Oasis School Science and Technology 10 New

Oasis School Science and Technology - 10 351 Step 2 : Once you are in camera, scroll along the bottom of your screen to find the video file. Step 3 : Press the record button on your screen to start the video recording . Step 4 : Press stop button (the same record button) to end the video recording. Some of the devices save the video automatically while others ask your permission. So you may press on ‘save’ button in such case. To find your recorded video, search either a videos application or a file application or gallery application. 2. Online video recording through application: There are several video recording applications available in the internet free of cost. applications like Droplr, FilmoraGo, XRecorder, Screencast-O-Matic, Vidma Recorder, Screencapture.com, etc. Such applications are provided with tutorials for their uses. Every video recording application can be used easily as per the settings and features of the application. Source: https://hotmart.com/en/blog/video-recording-apps B. Video cutting or trimming Video cutting or trimming is the process of removing the clip’s front or tail portions to create a new clip. It can be done through video editing applications both from mobiles and computers. 1. Video cutting in an android: In an android device, videos can be trimmed using built-in Gallery application. When you cut a video, you will not lose your original video, rather you create a new one. The steps given below can be followed to trim/ cut a video. Step 1 : Open the Gallery application on your device and tap on the video that you want to trim. Step 2 : Tap the pencil icon in the bottom left corner to get a new editing screen. Step 3 : Move the sliders at the bottom of the screen to mark the start and end of your video that you want to cut. Step 4 : Tap ‘save’ at the top right corner. Your trimmed video will be saved in the Gallery application. Source: https://www.howtogeek.com/201843/how-to-trim-and-cut-videos-on-yourandroid-device/ 2. Online video cutting: Video shooting and editing may be the hobbies of many students where you may have some large video files to cut. In internet, we can find several video cutters available for free. For example Gihosoft Free Video Cutter, Free Video Cutter, Media Cope, Video Edit Master, Free Video Cutter Joiner and so on. Almost every application has similar way of editing videos. Here, we discuss about the steps followed to trim videos through Free Video Cutter. Step 1 : Select and upload a video file from your device. Choose a video up to 1 hour long. Step 2 : Trim your clips by sliding the handlebars or by entering the time cuts manually. Step 3 : Instantly download your newly trimmed video clip.

352 Oasis School Science and Technology - 10 C. Video joining or merging It is the process of joining or combining of two or more video clips into a single clip. It is done by several applications available in the internet or by using built-in features of video merging in a phone. 1. Video merging in an android: Multiple videos can be merged into one by using builtin Gallery application in some of the android devices. To combine two or more videos, one can follow the steps given below. Step 1 : Start the Gallery application. Step 2 : Locate one of the videos that you want to merge. Step 3 : Tap the edit button (having the shape of a pencil) in the lower left corner of the screen. Step 4 : Add ‘Tap’ at the top of the screen and then choose a second video to combine with the first one. You can add multiple videos to make a single video file and then tap ‘Done’ when you are ready. Step 5 : Tap ‘Save’ at the top of the screen to save new combined-media video. If built-in applications are not present in the android then, the video merging can be done by installing few free applications in the phone. Such video editing applications are easily available in the internet. For example Video Merge, Kinemaster, Androvid, VidTrim, Video Joiner and so on. Such applications are provided with tutorials for their uses. Every video merging applications can be used easily as per the settings and features of the applications. 2. Online Video Merging in Computer: Some windows of computer are provided with built-in application to combine videos. Several applications are also available in the internet that can be used for joining two or more videos. Applications like FlexClip, Windows Photos application, EaseUS Video Editor, Windows Media Player, VLC Media Player, iMovie, and so on. Here, we discuss the method of merging videos using EaseUS Video Editor.

Oasis School Science and Technology - 10 353 Step 1 : Import the source videos by clicking ‘Import’ button or you may drag the videos to the appropriate area. Step 2 : Add the imported files to the video track by choosing the ‘Add to Project’ option, or you may drag and drop the videos to the track. Step 3 : Click on ‘Export’ to merge the videos. The free version of EaseUS Video Editor enables you to combine any number of MP4 files into one video most simply and securely. Source: https://multimedia.easeus.com/video-editor Activity 2 Prepare a power point presentation on the topic ‘Merits and Demerits of Internet’ and present them in your class. (Please include texts, pictures, audio-visuals, etc. in your presentation) Activity 3 Make a short video of your school by using the methods of recording, cutting and merging. Present them in your class. (Your video must include clips of school premises, labs,library, playground, different activities with background audio, etc.) Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. Internet service providers use broadband-based transmission. Internet service providers use broadband-based transmission because it can transmit audio, video and data over a very long distance. It is cheaper and faster. 2. Compare between modulator and demodulator. The comparison between modulator and demodulator are: SN Modulator SN Demodulator 1 It is done by the transmitter. 1 It is done by the receiver. 2 The modulation is necessary to add carrier signal and message signal and transfer it. 2 The demodulation is necessary to separate the message signal from the carrier signal. 3. Excessive screen time on social networking sites can cause mental illness. Excessive screen time is injurious to mental health. It can cause poor sleep and poor school performance. It can increase anxiety in children. Social networking sites can increase stress, depression and hatred in children. Children that spend more time in multimedia usually have a mood disorder. Those who spend more time on mobile will involve less in social activities, family gatherings and festivals. So, they cannot socialize properly. As a result, they will have difficulty maintaining important relations in future.

354 Oasis School Science and Technology - 10 As explained above excessive screen time on social networking sites can cause mental illness. 4. What kinds of activities are considered cyberbullying? Does digital technology promote bullying? The activities that are considered cyberbullying are: i. Texting hurtful, shameful or threatening messages on a mobile device. ii. Commenting hurtful things in someone's posts on social networking sites. iii. Posting something that hurts someone or some community. iv. Sharing harmful, false and mean content about someone else. Digital technology promotes bullying because the person does not need to be physically present there. They feel less or no guilt at all when commenting or posting mean because they are not face-to-face with them. It is easier to bully on social networking sites by making fake accounts also. 5. How can we be a reputed netizen? We can be reputed netizens if we are responsible and rational. i. We should value others' views. ii. We should be very careful before posting anything on social networking sites. iii. We should avoid fake news and stop sharing them. iv. We should respect the copyright. v. We should never bully others on social networking sites. 6. How does ICT facilitate business? Information and communication technology have facilitated business in many ways. Some of them are: i. Business companies can advertise their company and product on social networking sites. ii. Companies can sell their products online. iii. Consumers can use applications to purchase various products online. iv. Customers can pay for goods and services through mobile banking. v. Companies can keep records of their transactions in clouds. 7. We should practise digital well-being. We should practice digital well-being to: i. avoid lack of sleep. ii. improve the real-time relationship. iii. be more engaged and energetic. 8. How do the use and application of social networking sites affect a child? Mention its two positive effects and two negative effects on them. Social networking sites obviously affect the child. Many social networking sites are not even allowed for children. Some positive effects of social networking sites for children are: i. They can learn to communicate with others. ii. They can learn new in new ways, be more empathetic etc. Some adverse effects of social networking sites are:

Oasis School Science and Technology - 10 355 i. Over pressure and bad rumours on many subjects ii. Exposed to bullying, lack of sleep and concentration 9. What are the importance and advantages of digital transmission? The importance and advantage of digital transmission are: i. It can transfer data without alteration. ii. It can transfer data without interference. iii. It is cheaper and can be mass-produced. Exercises 1. Choose the best answer from the given alternatives. a. What is the signal that changes value with time? i. analog signal ii. digital signal iii. carrier signal iv. downlink b. Let’s suppose you comment something bad on a friend's Facebook, what is it called? i. cyberbullying ii. computer ethics iii. netizenship iv. cyber laws c. Why should we be very careful before posting on social networking sites? i. it can consume our data ii. people can track our digital footprint which can damage our reputation in future iii. the photo we post may not be beautiful iv. we should not think much about posting d. What is the disadvantage of broadband connection? i. the cost of installation is high ii. it can transfer voice, video and data iii. it can transfer more bandwidth iv. it can transfer data to longer distance e. Which one of the following represents analog signal? i. medium wave radio ii. infrared thermometer iii. smartphones iv. computers f. What is represented by the habit of posting personal details too much on the internet? i. digital well being ii. cautions for digital well being iii. challenges to digital well being iv. application of digital well being

356 Oasis School Science and Technology - 10 2. Define the following terms with required examples. a. Information and technology b. Signal c. Analog signal d. Digital signal e. Bit f. Byte g. Digital signal transmission h. Baseband transmission i. Broadband transmission j. Cyberbullying k. Netizen l. Netizenship m. Online reputation n. Online reputation management o. Modulation p. Demodulation 3. Answer the following questions in very short. a. What kind of signal is used by digital electronics such as computers and mobiles? b. Write the full form of LAN. c. Write uses of broadband transmission. d. Write two examples of cyberbullying. e. What does it mean by digital well-being? f. What represents 1 bit and 1 byte? g. Write the steps for transmission of the digital signal. h. Give two examples of digital signals. 4. Give reasons. a. ICT is essential for us. b. Broadband transmission is better than baseband transmission. c. Broadband transmission is used in the telephone network. d. Digital technology is widespread in our society. e. Digital technology can have negative psychological consequences. f. Digital footprint is important. g. We should be able to manage our online reputation. h. Audio-visual recording is important for scientists and others. i. We must practice digital well-being. 5. Differentiate between the following. a. Analog signal and digital signal b. Bit and byte c. Baseband transmission and broadband transmission d. Modulator and demodulator e. Aanalog communication and digital communication f. Digital well-being and digital reputation

Oasis School Science and Technology - 10 357 6. Answer the following questions in short. a. What are the advantages and disadvantages of baseband transmission? b. What are the advantages and disadvantages of broadband transmission? c. How can we cut an audio file? d. How can we merge multiple audio files? e. What factors affect the online reputation? f. How has ICT facilitated the educational process? g. What are the importance and advantages of digital transmission? h. Give a few examples of digital technology used in our daily life. i. Discuss the role of digital technology in the development of information and communication technology. j. Write any four advantages and precautions of digital well-being. k. Write the importance of digital reputation management. l. Write any two advantages and disadvantages of digital technology in our daily life. 7. Answer the following long questions. a. What is digital technology? How is it advantageous to human life? Discuss. b. Digital technology can be dangerous for our society. Discuss. c. Let’s suppose we are a very popular person on social networking sites. What set of socially acceptable behaviour we must follow? d. Let’s suppose we are active on social networking sites. How should we manage our online reputation? e. What is audio-visual recording? How are audio and video recorded from android mobiles? f. How is a video cut into multiple videos and how are multiple videos merged into one? g. How does the internet help to decrease social crimes? h. List a person's or company's various activities that harm their online reputation. i. List the characteristics of good netizens. j. Explain the relationship between netizen, netizenship and netiquette. k. Write any two positive effects and two negative effects of the use and application of social networking sites.

358 Oasis School Science and Technology - 10 Key terms and terminologies 1. Classification of elements: The grouping of elements according to their similarities and differences is called the classification of elements. 2. Mendeleev's periodic law: According to Mendeleev's periodic law, "the physical and the chemical properties of elements are the periodic functions of their atomic masses." 3. Mendeleev's periodic table: The table or chart which is obtained after arranging elements based on increasing atomic masses is called Mendeleev's periodic table. 4. Modern periodic law : According to Modern periodic law, "the physical and the chemical properties of elements are the periodic functions of their atomic numbers." 5. Modern periodic table : The table or the chart which is obtained after arranging elements based on their increasing atomic numbers is called the modern periodic table. 6. Lanthanides : The 15 elements from cerium (58Ce) to lutetium (71Lu) along with lanthanum (57La) are called Lanthanides. 7. Actinides : The 15 elements from thorium (90Th) to lawrencium (103Lr) along with actinium (89Ac) are called Actinides. UNIT 14 CLASSIFICATION OF ELEMENTS Estimated teaching periods Theory 7 Practical 2 • Modern periodic law • Introduction to modern periodic table • Structure of modern periodic table, group and period • Sub-electronic configuration of the first 20 elements • s, p, d and f block elements of periodic elements • Position of metals, nonmetals and metalloids in the modern periodic table • Periodic variation (variation of atomic size, electropositivity, electronegativity, valency and reactivity) The Sequence of Curriculum Issued by CDC Dmitri Ivanovich Mendeleev is well known for his periodic table. He was born in Russian Empire on 8th February 1834 and demised on 2nd February 1907. He was an inventor and a chemist. He formulated a periodic law based on atomic weight and arranged available elements in Mendeleev’s periodic table. He was honoured with the Davy medal, Faraday Lectureship Prize etc. About the Scientist D. I. Mendeleev

Oasis School Science and Technology - 10 359 8. Alkali metals : Elements of group IA are called alkali metals except for hydrogen. They dissolve with water to produce strong water-soluble bases called alkali. 9. Alkaline earth metals : Elements of the IIA group are called alkaline earth metals. They are found on the earth's crust and react with water to give hydroxides. 10. Transition metals : The elements that lie from the 3rd column (IIIB) to the 12th column (IIB) are called transition metals. They are d-block elements. 11. Halogens : The elements of group VIIA(17) are called halogens because they can react with metals to produce salts. 12. Inert gas : The zero group elements are called inert gas. 13. Periods : The horizontal rows of the periodic table where elements with gradual changes in characters and atomic numbers are kept are called periods. 14. Groups : The vertical columns of the periodic table where elements with similar characteristics are kept are called groups. 15. Sub-shells : Sub-shellls are the regions in main shells, where the probability of finding electrons is maximum. 16. Aufbau principle : According to the Aufbau principle, "filling of electrons always occurs from the lower energy level to the higher energy level." 17. Electronic configuration : The distribution of electrons in different shells and sub-shells is called electronic configuration. 18. s-block elements : The elements which have the last electron in the s- subshell are called s-block elements. 19. p-block elements : The elements which have the last electron in the p-subshell are called p-block elements. 20. d-block elements : The elements which have the last electron in the d-sub shell are called d-block elements. 21. f-block elements : The elements which have the last electron in the f-sub shell are called f-block elements. Introduction Classification of elements refers to the process of grouping elements based on their similarities and dissimilarities. In the initial stage of the study of science, very few elements were known to us. These elements could be studied individually. With the rapid development of scientific research, more and more new elements with their different physical and chemical properties are discovered. Till now, one hundred eighteen elements with different atomic masses and numbers are known to us. Among them 92 are natural whereas 26 are synthesized in the laboratory. So, it is quite difficult to study these elements separately. To solve this problem, chemists realized that elements with similar properties should be classified into one group. The grouping of elements according to their similarities and differences is called the classification of elements. After classification, elements are arranged in a table called periodic table. Thus, the table in which elements are arranged in rows and columns based on certain law is called the periodic table. Mendeleev's Period Law Russian chemist Dmitri Mendeleev followed the idea which was given by John Newland in 1864 AD. At this time, about 63 elements were known to people. Mendeleev studied the physical and chemical properties of these elements as well as their compounds. After the

360 Oasis School Science and Technology - 10 complete study of these elements, he made a sequence of elements in ascending order of atomic masses similar to the sequence which was given by John Newland in 1864 AD. In this sequence, he found that elements with similar properties occur at regular intervals. This observation led Mendeleev to conclude a law, which is called Mendeleev's periodic law. According to Mendeleev's periodic law, "the physical and the chemical properties of elements are the periodic functions of their atomic masses." It means that when elements are arranged based on increasing atomic masses, the elements having similar physical and chemical properties are repeated after a regular interval. In the above periodic law, the meaning of periodic function is such that the properties of elements go on changing when atomic mass is increased but after a certain regular interval; they repeat the characteristics of the previous element. Mendeleev's Periodic Table After the study of the physical and chemical properties of elements, Mendeleev proposed his periodic law. Based on this law, he arranged elements according to the increasing atomic masses. As a result, he founded a table called Mendeleev's periodic table. The table or chart which is obtained after arranging elements based on increasing atomic masses is called Mendeleev's periodic table. In Mendeleev's periodic table, there are seven horizontal rows called periods, and eight vertical columns called groups. Sometimes periods are also called series and groups are also called families. In this table, elements with similar physical and chemical properties fall under groups and elements with a gradual change in characteristics fall under periods. During the time of Mendeleev, only 63 elements were known to us, so he left some gaps for undiscovered elements. A part of Mendeleev's periodic table is given below: Fig: A part of Mendeleev's periodic table Fact File Dmitri Ivanovich Mendeleev is called the Father of the Periodic Table.

Oasis School Science and Technology - 10 361 Characteristics of Mendeleev's periodic table i. Mendeleev arranged elements based on increasing atomic masses. ii. In this table, there are seven horizontal rows (periods) and eight vertical columns (groups). iii. In Mendeleev's periodic table, he left gaps for undiscovered elements. For example; scandium, gallium, germanium, etc. iv. Each group of Mendeleev's periodic table was further divided into two sub-groups, which were sub-group A and sub-group B. v. Inert gases like He, Ne, Ar, Kr, Xe and Rn were not discovered during the time of Mendeleev, so there was no separate place for them. Modern Periodic Law To overcome the defects of Mendeleev's periodic table, a group of chemists led by Henery Moseley studied the physical and chemical properties of elements in 1913 AD with the help of x-ray spectra. They concluded that atomic number is more fundamental property of elements rather than their atomic masses. This conclusion was quite satisfactory for an atom because the chemical properties of elements depend upon the number of electrons present in its atom. With the help of the above study, Henry Moseley modified Mendeleev's periodic law. This modified law is called modern periodic law. According to Modern periodic law, "the physical and the chemical properties of elements are the periodic functions of their atomic numbers." It means that when elements are arranged based on their increasing atomic number, at a regular interval, the properties of elements are repeated. While making the sequence of elements based on their increasing atomic number, it is found that the elements which have similar physical and chemical properties lie in the same vertical column. Similarly, the elements with a gradual change in properties lie in the same horizontal row one after another. Modern Periodic Table After the complete study of the physical and chemical properties of elements and their compounds, the team of Henry Moseley proposed the modern periodic law, which is a modified form of Mendeleev's periodic law. With the help of this modern periodic law, Bohr arranged elements based on increasing atomic numbers. As a result of this, he found a table called the modern periodic table. The table or the chart which is obtained after arranging elements based on their increasing atomic numbers is called the modern periodic table. In the modern periodic table, there are seven horizontal rows called periods. In these periods, elements with gradual changes in characters lie one after another. Similarly, in this table, there are a total of nine groups starting from the Roman number I to VIII and zero (total 18 groups according to IUPAC). In these groups, elements with similar physical and chemical properties fall one below another.

362 Oasis School Science and Technology - 10 Fig: Modern periodic table Advantages of Modern Periodic Table. In the modern periodic table, elements are classified based on increasing atomic numbers. This system of classification helps to solve the defects of Mendeleev's periodic table in the following ways. 1. Position of hydrogen The position of hydrogen has not yet been solved completely. But as its atomic number is the least (i.e. one), it is placed in group IA of the modern periodic table along with alkali metals. Reasonable Fact Two reasons why hydrogen is kept in group 1 in the periodic table. Two reasons for keeping hydrogen in group 1 in the periodic table are: (i) Hydrogen has one electron in its shell. (ii) Hydrogen can lose one electron like other elements of group 1. Alkali metals are more reactive. The atoms of alkali metals have only one electron in their outermost orbit. They are bigger and have less ionization potential than other elements in their period. Therefore, alkali metals are more reactive to obtain octet state. 2. Position of isotopes Isotopes are atoms of the same elements, which have the same atomic numbers but different atomic masses. Therefore, isotopes of one element are placed together in the same group. For example, there are three isotopes of carbon (i.e. 6 C12, 6 C13 and 6 C14) with the same atomic numbers placed together in IVA group of the modern periodic table.

Oasis School Science and Technology - 10 363 3. Correction of the wrong position of elements When elements are arranged based on their increasing atomic numbers, the wrong position of argon, potassium, nickel and cobalt is solved automatically without changing their own places. 4. Position of alkali metals and coinage metals In the modern periodic table, the most reactive alkali metals are placed in IA group whereas the least reactive coinage metals are placed in IB group. 5. Position of lanthanides and actinides In the modern periodic table, fifteen elements of the lanthanide series (starting from La to Lu) and fifteen elements of the actinide series (starting from (Ac to Lr) are placed in a separate box below the main periodic table. The 15 elements from cerium (58Ce) to lutetium (71Lu) along with lanthanum (57La) are called Lanthanides and other 15 elements from thorium (90Th) to lawrencium (103Lr) along with actinium (89Ac) are called Actinides. Characteristics of Modern Periodic Table. The main features of the modern periodic table are given below. i. In the modern periodic table, elements are arranged based on their increasing atomic numbers. ii. In this table, there are seven periods and nine groups (eighteen groups in a modified or a long form of the periodic table given by IUPAC). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 IA IIA IIIB IVB VB VIB VIIB VIIIB VIIIB VIIIB IB IIB IIIA IVA VA VIA VIIA 0 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Be Kr iii. Inert gases like He, Ne, Ar, Kr, Xe and Rn are placed in a separate group (zero group) at the extreme right side of the table. iv. In the modern periodic table, metals are kept on the left-hand side, non-metals on the right-hand side and metalloids are placed between metals and non-metals. v. In this table, hydrogen is placed in IA group and lanthanides and actinides are placed in a separate box below the main table. vi. Except zero and VIII, all the groups of the modern periodic table are further divided into two sub-groups A and B. vii. Based on sub-shells, elements are divided into four blocks. They are s-block, p-block, d-block and f-block. Classification of Elements in the Modern Periodic Table Elements are broadly classified as metals, non-metals and metalloids in the modern periodic table. a. Metal Metals are electropositive elements. They tend to lose electrons. They are very good conductors of heat and electricity. They are usually solid, tensile, malleable and ductile. They are kept on the left-hand side of the periodic table.

364 Oasis School Science and Technology - 10 (i) Alkali metals: Elements of group IA are called alkali metals except for hydrogen. They dissolve with water to produce strong water-soluble bases called alkali. Metals of the IA group are bigger and more reactive than other metals of the same period. They are lighter and softer than other metals. They are s-block elements. Lithium, sodium and potassium are some IA elements. 2Na + 2H2 O 2NaOH + H2 2K + 2H2 0 2KOH + H2 Reasonable Fact Lithium and sodium are kept in group 1. Both lithium and sodium contain one valence electron, and both of them react with water to produce corresponding alkali and hydrogen gas. So, lithium and sodium are placed in group IA of the modern periodic table. (ii) Alkaline earth metals: Elements of the IIA group are called alkaline earth metals. They include magnesium (Mg), calcium (Ca), etc. They are found on the earth's crust and react with water to give hydroxides. Mg + 2H2 0 Mg (OH)2 + H2 Ca + 2H2 0 Ca (OH)2 + H2 They are less reactive than IA metals. They are s-block elements. Elements of the IIIA group except boron are metals. They can form metal oxides and metal hydroxides. They are less reactive than the IIA group. They are p-block elements. Aluminium and gallium are some IIIA elements. (iii) Transition metals: The elements that lie from the 3rd column (IIIB) to the 12th column (IIB) are called transition metals. They are d-block elements. They have variable valency. Gold, copper, silver and iron are some transition elements. (iv) Lanthanides and actinides: Lanthanides and actinides are kept below the modern periodic table. They are f-block elements. Cerium and europium are some lanthanides. Uranium and plutonium are some actinides. b. Metalloids The elements of the IVA group are usually metalloids. Boron of the IIIA group is also a metalloid. Metalloids have intermediate properties between metals and nonmetals. They can pass electricity at higher temperatures. They are used to make semiconductors. Boron, silicon, germanium etc. are some metalloids. c. Non-metals Non-metals are electronegative elements. They tend to gain electrons. They are mostly insulators. They are usually liquid or gas. They are non-malleable and nonductile. They are kept on the right-hand side of the modern periodic table. Nonmetals are mostly p-block elements except hydrogen and helium. The elements of the group VA, VIA, VIIA and zero group are non-metals. Nitrogen, phosphorus etc. are some elements of the VA group. They react with oxygen to form various acidic oxides. Oxygen, sulphur etc. are some elements of the VIA group. They can react with metals. (i) Halogens: The elements of group VIIA(17) are called halogens because they can react with metals to produce salts. Fluorine, chlorine and bromine are

Oasis School Science and Technology - 10 365 some elements of VIIA group. They are more reactive than the other nonmetals of the same period. (ii) Inert gas: The zero group elements are called inert gas. Elements of zero group are neon, argon etc. They are p-block elements except for helium. They are either in a duplet or octet state. They do not take part in the chemical reaction. They are larger than the other non-metals of the same period despite having greater nuclear charge because they are stable atoms. Position of Elements in the Modern Periodic Table i. Position of hydrogen Hydrogen has only one shell with one electron. To complete a duplet, it gains one electron like halogens (F, CI, Br and I) and sometimes, it loses one electron like alkali metals (Li, Na, K, etc.). Due to the above-mentioned reasons, the position of hydrogen is still controversial, but due to its one atomic number, it is placed under IA group of the modern periodic table along with alkali metals. ii. Position of metals, non-metals and metalloids In the modern periodic table, metals are present on the left-hand side, non-metals are present on the right-hand side and metalloids are placed between metals and non-metals. iii. Position of lanthanides and actinides The 15 elements from cerium (58Ce) to lutetium (71Lu) along with lanthanum (57La) are called Lanthanides and other 15 elements from thorium (90Th) to lawrencium ( 103Lr) along with actinium (89Ac) are called Actinides. These thirty elements (15 lanthanides and 15 actinides) are kept separately in a separate box below the main periodic table. These elements have dissimilar characters from other elements of the rest of the periodic table. iv. Position of inert gases He, Ne, Ar, Kr, Xe and Rn are called inert gases as they do not participate in chemical reactions. These elements, which have zero valency are kept in the zero group, at the extreme right-hand side of the modern periodic table. Reasonable Fact Argon atoms can exist freely in nature. The outermost orbit of Argon atom is filled with eight electrons. They are stable by octet. Due to this, it does not take part in the chemical reaction. Therefore, the argon atom can exist freely in nature. Differences between Mendeleev's Periodic Table and Modern Periodic Table SN Modern Periodic Table SN Mendeleev's Periodic Table 1 The modern periodic table is obtained after arranging elements based on increasing atomic numbers. 1 Mendeleev's periodic table is obtained after arranging elements based on increasing atomic masses. 2 In this table, there are seven periods and eighteen groups. 2 In this table, there are seven periods and eight groups. 3 Hydrogen, isotopes, lanthanides and actinides are kept properly in this table. 3 The proper position for hydrogen, lanthanides and actinides is not allocated in this table.

366 Oasis School Science and Technology - 10 Periods and Groups of the Modern Periodic Table Periods In the modern periodic table, there are seven horizontal rows called periods. In each period, there are fixed numbers of elements with gradual changes in atomic numbers and characteristics. As we move from left to right in the period, the size of atoms decreases but the atomic number increases. Thus, horizontal rows of the periodic table where elements with gradual changes in characters and atomic numbers are kept are called periods. All seven periods of the modern periodic table are divided into five groups based on the number of elements present. They are as follows: Very short period: It includes only the first period. In this period, there are only two elements, namely hydrogen and helium. Short periods: It includes the second and third periods. In these periods, there are eight elements each. Long periods: It includes the fourth and fifth periods. In these periods, there are eighteen elements each. Very long periods: It includes the sixth and seventh periods. In these periods, there are thirty-two elements each. S.N. Period Number of Elements Types of Periods 1 First 2 Very short period 2 Second 8 Short period 3 Third 8 Short period 4 Fourth 18 Long period 5 Fifth 18 Long period 6 Sixth 32 Very long period 7 Seventh 32 Very long period Groups The vertical columns of the periodic table are called groups. There are a total of 18 groups (starting from the Roman number I to VIII, and zero) in the modern periodic table. In these groups, elements with similar characteristics fall one below another. Thus, vertical columns of the periodic table where elements with similar characteristics are kept are called groups. Except for zero and VIII groups, all other groups are further divided into sub-groups A and B. In the eighth group, there are three vertical columns but they are not represented by A, B and C. Altogether, there are a total of eighteen vertical columns, which are also called 18 groups in the long form modern periodic table. It is based on IUPAC system. Groups Sub-groups Groups based on IUPAC Group I Sub-groups IA and IB 1 and 11 Group II Sub-groups IIA and IIB 2 and 12 Group III Sub-groups IIIA and IIIB 13 and 3

Oasis School Science and Technology - 10 367 Group IV Sub-groups IVA and IVB 14 and 4 Group V Sub-groups VA and VB 15 and 5 Group VI Sub-groups VIA and VIB 16 and 6 Group VII Sub-groups VIIA and VIIB 17 and 7 Group VIII Three vertical columns 8, 9 and 10 Group Zero Single column 18 Total Groups=Nine Total Vertical Columns=Eighteen Total =18 groups Differences between Periods and Groups SN Periods SN Group 1 The horizontal rows of the periodic table are called periods. 1 The vertical columns of the periodic table are called groups. 2 Elements in the same period can have different valency. 2 Elements in the same group have the same valency. 3 Each element of the same period has an equal number of orbits. 3 The number of orbits increases in each element from top to bottom. 4 Atomic size decreases from left to right in a period. 5 Atomic size increases from top to bottom in a group. Characteristics of Periods and Groups 1. Atomic size The distance between the nucleus and the outermost shell of an isolated gaseous atom is called atomic size. When we move from top to bottom in the group, the size of atoms increases as the number of additional shells increases. Similarly, when we move from left to right in a period, the size of atoms decreases as a nuclear force of attraction increases.

368 Oasis School Science and Technology - 10 2. Ionization potential (Nuclear power) The amount of energy required to remove the loosely bonded outermost electron from an isolated gaseous atom is called ionization potential. It increases with the decreasing size and decreases with the increasing size. Therefore, in the period left to right, it increases and in the group top to bottom, it decreases. 3. Valence electrons The total number of electrons present in the outermost shell of an atom are called valence electrons. It increases in the period and remains same in the group. 4. Valency The total number of electrons either gained or lost or shared with an atom during the chemical combination is called valency. In the period, from left to right, it first increases up to four and then decreases up to zero. In groups from top to bottom, it remains the same. Element: Li Be B C N O F Ne Valency: 1 2 3 4 3 2 1 0 5. Electropositivity and Electronegativity The tendency of an atom to donate an electron is called electropositivity. The electropositivity of an element increases down the group and decreases from left to right in the period. The amount of energy required for an atom to attract foreign electrons towards itself is called electronegativity. It increases with the decreasing size and decreases with the increasing size. In the period, from left to right it increases and in the group from top to bottom it decreases. 6. Metallic characters Metallic characters increase from top to bottom in the group and decrease from left to right in a period. Sub-shells (Orbitals) Orbitals or sub-shells are the regions in the orbits where electrons are most likely to be found. Each orbital has a distinct shape. For example, s-orbital is spherical. Based on the 2n2 formula, when there are two electrons in the outermost shell of an atom, it is called duplet (for example helium). Similarly, when there are eight electrons in the outermost shell, it is called an octet such as Ne, Ar, Kr, Xe and Rn. The electronic configuration of all the elements cannot be explained by the 2n2 formula. Thus, the concept

Oasis School Science and Technology - 10 369 of sub-shells was proposed. According to this concept, every main shell contains one or more sub-shells, which are denoted by s, p, d and f. Different shells contain different numbers of sub-shells. The shells with their sub-shells are given in the table. Main shell Sub-shells (Orbitals) Main shell first (n=1) s Main shell second (n=2) s and p Main shell third (n=3) s, p and d Main shell fourth (n=4) s, p, d and f The s- sub-shell may contain a maximum of two electrons. The p- sub-shell may contain a maximum of six electrons. The d- sub-shell may contain a maximum of ten electrons. The f- sub-shell may contain a maximum of fourteen electrons. Based on the above data, we can co-relate the 2n2 formula with sub-shells (s, p, d and f). The main shell, its sub-shells and the maximum number of electrons present there can be summarized as follows: Main shell Sub-shells Total electrons K (n = 1) 1s 2 L (n = 2) 2s, 2p 2 + 6 = 8 M (n = 3) 3s, 3p, 3d 2 + 6 + 10 = 18 N (n = 4) 4s, 4p, 4d, 4f 2 + 6 + 10 + 14 = 32 Aufbau Principle According to the concept of the sub-shell, every main shell contains one or more sub-shells, which are represented by s, p, d and f. There is a difference in the energy level of these sub-shells. The entering of electrons always occurs from the lower energy level to the higher energy level. So, according to the Aufbau principle, "filling of electrons always occurs from the lower energy level to the higher energy level." To find out the sequence of the energy levels of different subshells, an arrow diagram is given below. Based on the arrow diagram, the sequence of energy levels is given below : 1s< 2s< 2p< 3s< 3p< 4s< 3d< 4p< 5s< 4d< 5p< 6s< 4f < 5d < 6p < 7s........ Fact File The aufbau principle cannot describe electronic configuration of copper and chromium. Electronic Configuration The distribution of electrons in different shells and sub-shells is called electronic configuration. Based on the Aufbau principle, the electronic configuration of some Fig: Aufbau’s principle

370 Oasis School Science and Technology - 10 elements in different shells and the sub-shells is given in the table below. Atomic Number Name Symbol Electronic configuration Based on shells Based on subshells K L M N 1 Hydrogen H 1 1s1 2 Helium He 2 1s2 3 Lithium Li 2 1 1s2 , 2s1 4 Berylium Be 2 2 1s2 , 2s2 5 Boron B 2 3 1s2 , 2s2 2p1 6 Carbon C 2 4 1s2 , 2s2 2p2 7 Nitrogen N 2 5 1s2 , 2s2 2p3 8 Oxygen O 2 6 1s2 , 2s2 2p4 9 Fluorine F 2 7 1s2 , 2s2 2p5 10 Neon Ne 2 8 1s2 , 2s2 2p6 11 Sodium Na 2 8 1 1s2 , 2s2 2p6 , 3s1 12 Magnesium Mg 2 8 2 1s2 , 2s2 2p6 , 3s2 13 Aluminium Al 2 8 3 1s2 , 2s2 2p6 , 3s2 3p1 14 Silicon Si 2 8 4 1s2 , 2s2 2p6 , 3s2 3p2 15 Phosphorus P 2 8 5 1s2 , 2s2 2p6 , 3s2 3p3 16 Sulphur S 2 8 6 1s2 , 2s2 2p6 , 3s2 3p4 17 Chlorine Cl 2 8 7 1s2 , 2s2 2p6 , 3s2 3p5 18 Argon Ar 2 8 8 1s2 , 2s2 2p6 , 3s2 3p6 19 Potassium K 2 8 8 1 1s2 , 2s2 2p6 , 3s2 3p6 , 4s1 20 Calcium Ca 2 8 8 2 1s2 , 2s2 2p6 , 3s2 3p6 , 4s2 Fig: subshell electronic configuration of first 20 elements Classification of Elements based on Subshell-electronic Configuration According to the sub-shells electronic configuration, the elements and the periodic table are divided into four parts called blocks. The four different blocks are described below: i. s-block The block of alkali metals (IA) and alkaline earth metals (IIA) which are present on the left-hand side of the periodic table is called an s-block. The elements which have the last electron in the s- subshell are kept in this block. Examples of these elements are Li, Na, K, Rb, Cs, Be, Mg, Ca, etc. ii. p-block The block of metals, non-metals, metalloids and inert gases which are present in IIIA, IVA, VA, VIA, VIIA and zero groups is called p-block. It is present on the righthand side of the modern periodic table. The elements which have the last electron

Oasis School Science and Technology - 10 371 in the p-subshell are kept in this block. For example; C, N, O, F, CI, etc. iii. d-block The block of transitional metals which is present in the middle part of the modern periodic table is called a d-block. This block includes elements of IB to VIIB and VIllth groups. The d-block is present between the s-block and the p-block, so it is also known as the transitional block. The elements which have the last electron in the d-sub shell are called d-block elements. For example; Ag, Au, Fe, Cu, etc. iv. f-block The block of lanthanides and actinides which is present below the main periodic table is called f-block. The elements which have the last electron in the f-sub shell are kept in this block. It is also called the block of inner transitional elements as it is taken out from the transitional block. In this block, there are only 28 elements. For example; Ce, Th, U, etc. Chemical Reactivity of Elements Metals have 1, 2 and 3 electrons in their last shell and non-metals have 5, 6 and 7 electrons in their last shell. According to the duplet and octet rules, metals lose electrons and nonmetals gain electrons to make stable electronic configurations. The metal which loses electrons easily is called a reactive metal, and the non-metal which gains electrons easily is called a reactive non-metal. There are several factors which affect the reactivity of elements, such as size, ionization, potential, electronegativity, etc. Reactivity of metals Sodium and potassium both are metals. They have one electron in their valence shell but potassium loses its valence electron more easily than sodium. This is because potassium has a bigger atomic size and less nuclear force of attraction as compared to sodium. Na 1 2 3 Sodium atom K Potassium Atom Reasonable Fact Potassium is more reactive than sodium although they both belong to the same group. Potassium is more reactive than sodium because the atomic size of the potassium atom is larger than that of sodium. So, the valence electron of potassium can more easily be taken by other reacting atoms as compared to that of sodium. Hence, potassium is more reactive than sodium.

372 Oasis School Science and Technology - 10 From the above example, it is clear that the metal atom which has a bigger atomic size with a less nuclear force of attraction (ionization potential) loses its outermost valence electron easily in the process of chemical combination. We have already discussed that in the periodic table, atomic size increases in groups and decreases in the period. Therefore, the reactivity of metals also differs in these two cases. Reactivity of metals in groups In the modern periodic table, as we move from top to bottom, the size of atoms increases as an additional shell is added. A bigger atomic size having less ionization potential (nuclear force of attraction) loses electrons more easily. Therefore, the reactivity of metals increases in the group as we move from top to bottom. Reasonable Fact Elements of Group IA, IIA and IIIA (or group 1, 2 and 13) are more reactive as we go down in the group of the periodic table. Elements of Group IA, IIA and IIIA (or group 1, 2 and 13) are more reactive as we go down in the group because of the following reasons: (i) Atomic radius of these elements increases as we go down in the group. (ii) Ionization potential decreases as we go down in the group. Reactivity of metals in periods In the modern periodic table, as we move from left to right, the size of its atoms decreases as a nuclear force of attraction increases. In this condition, it is difficult to lose electrons from the outermost shell of an atom. Therefore, the reactivity of metals decreases as we move from left to right in periods of the modern periodic table. Reactivity of non-metals Fluorine and chlorine are both non-metals. They have seven electrons in their valence shell. During the process of chemical combination, fluorine gains one electron easily as compared to chlorine. This is because fluorine having a small atomic size and more electronegativity gains electron easily and becomes more reactive. This discussion leads to the conclusion that a nonmetal atom with a smaller atomic size is more reactive than one with a bigger atomic size. Li Least reactive metal Most reactive metal Chemical reactivity of metals increases on moving down in a group Na K Rb Cs Fr Group 1 Most reactive non-metal Least reactive non-metal Reactivity of non-metals decreases on moving from top to bottom in a group F Cl Br I At Group VIIA/17

Oasis School Science and Technology - 10 373 F Cl Fig: Fluorine atom Fig. Chlorine atom Reactivity of non-metals in groups In the modern periodic table, while we move from top to bottom in the group, the size of atoms increases and electronegativity decreases. Therefore, the reactivity of non-metals also decreases. Reasonable Fact Elements of group VA, VIA and VIIA (or group 15, 16, and 17) are less reactive as we go down in the group of the Modern periodic table, why? The atomic size of elements increases as we move downwards in groups. The elements of group VA, VIA and VIIA (or group 15, 16 and 17) are non-metals. The chemical reactivity of non-metals decreases when the atomic size of those elements increases. Therefore, the elements of group VA, VIA and VIIA (or group 15, 16 and 17) are less reactive as they go down in the group of the Modern periodic table. Why is fluorine more active than chlorine although both lie in the same group? Since the atomic size of fluorine is smaller than that of chlorine, nuclear attraction is more on the valence shell of the fluorine atom. As a result, fluorine can get one electron more easily during the chemical reaction. Therefore, fluorine is more reactive than chlorine although both of them belong to the same group. Reactivity of non-metals in periods In the modern periodic table, as we move from left to right, the size of atoms decreases as nuclear force of attraction increases. In this condition, it is easy to gain electrons for a non-metal atom. Therefore, the reactivity of non-metals increases as we move from left to right in periods of the modern periodic table. Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. The size of nonmetals is smaller than metals of the same period. Nonmetals are smaller than metals if they are in the same period. The reason is the increase in nuclear charge (charge of protons). Metals are on left and non-metals are in right. When going from left to right the number of protons in the nucleus increases. The increase in the nuclear charge attracts the valance electrons more strongly pulling them closer to the nucleus. As a result, atomic size decreases across the period.

374 Oasis School Science and Technology - 10 2. Electrons go to the ‘4s’ subshell of the fourth orbit even though there is room in the ‘3d’ subshell of the third orbit in case of K and Ca. Electrons go to the ‘4s’ subshell of the fourth orbit even though there is room in the ‘3d’ subshell of the third orbit because 4s is at low energy level than 3d. Electrons always arrange themselves in the lowest possible energy level according to Aufbau’s principle. 3. Calcium belongs to the fourth-period, IIA group. The electronic configuration of calcium is [K(2), L(8), M(8) and N(2)]. Since there are four orbits, calcium belongs to the fourth period.There are two valance electrons in the last orbit(N). So, it belongs to the IIA group. 4. Even though magnesium has more protons and electrons than sodium, it is still smaller than sodium. Why? Magnesium has 12 protons and 12 electrons. Sodium has 11 protons and 11 electrons. Even though magnesium has more protons and neutrons, it is smaller than sodium. The reason is a nuclear charge. The nucleus of magnesium has more nuclear charge than sodium. The nucleus of magnesium attracts electrons more strongly than sodium. As a result, the magnesium atom shrinks more than the sodium atom. Hence, the magnesium atom becomes smaller than the sodium atom. 5. Larger atoms of metals are more reactive than the smaller atoms of metal. The main property of the metal is its ability to lose electron. It should have less ionization potential and less electronegativity to lose electrons easily. If the atoms of metal are larger, the valance electrons will be farther away from the nucleus. As a result, electrons will be held loosely. It means the atom has less ionization potential and less electronegativity. Therefore, larger atoms of metal can lose electrons easily. If atoms of metal are smaller, electrons will be closer to the nucleus. Electrons will be held strongly. It means the atom has greater ionization potential and greater electronegativity. Therefore, a small atom of metal cannot lose electrons easily.Therefore, we can conclude that larger atoms of metals are more reactive than smaller atoms of metals. 6. Oxygen is an element. Why is it considered non-metal? Why its valency is 2? Oxygen has an electronic configuration of [K(2), L(6)]. Its valance orbit has six electrons. To be stable by the octet rule, oxygen needs to take two electrons from other elements. Since it can take electrons, it is called non-metal. Since it can take two electrons, its valency is 2. 7. Helium is ‘s’ a block element but it is kept with p-block elements in the modern periodic table. Helium is a ‘s’ block element but it is kept in p-block element in the modern periodic table because it is an inert element. Unlike other ‘s’ block elements, it does not take part in chemical reaction. So, it is kept with inert ‘p’ block elements. 8. A hypothetical sequence with an electronic configuration of some elements is given below. With the help of this sequence, answer the following questions. Elements A B C D E F G H configuration 2,1 2,2 2,3 2,4 2,5 2,6 2,7 2,8 i. Which period elements are given in the table? These elements lie in the second period of the modern periodic table because they have two shells in their electronic configuration.

Oasis School Science and Technology - 10 375 ii. What will be the valency number of the element when we move from left to right? The valency number of these elements first increases from 1 to 4 and then decreases up to zero. iii. Identify metal, non-metal, metalloid and inert gas from the sequence. In the given table, A, B and C are metals as they have 1, 2 and 3 electrons in their valence shell which they tend to lose for stability. D is a metalloid as it has four electrons in the valence shell which it is likely to share. E, F and G are nonmetals as they have 5, 6 and 7 electrons in their valence shell , so they tend to gain electron. H is called inert gas because it has 8 electrons in the valence shell. So, it does not not lose or gain electron to be stable. iv. Write the variation of atomic sizes as we move from left to right in the sequence. The size of these elements decreases as we move from left to right in the sequence. This is because the nuclear force of attraction of these elements increases with the increase in the number of protons. Exceptionally, H has a bigger atomic size because it is a stable atom. 9. On the basis of the given electronic configuration answers the following questions. A = 1s2 , 2s2 2p6 , 3s1 B = 1s2 , 2s2 2p6 , 3s2 3p6 , 4s1 C = 1s2 , 2s2 2p5 D = 1s2 , 2s2 2p6 , 3s2 3p5 i. Identify period, group, valency, metallic nature and block of the above elements. Element Period Group Valency Reactivity Block A 3 IA 1 Reactive metal s B 4 IA 1 Reactive metal s C 2 VII A 1 Reactive nonmetal p D 3 VII A 1 Reactive nonmetal p ii. Name the compound formed between A with D and B with C. The compound formed by the reaction between A and D is sodium chloride (NaCl). The compound formed by the reaction between B and C is potassium fluoride (KF) iii. Which is more reactive between: a) A and B b) C and D Between A and B, B is more reactive as it has a bigger atomic size, less ionization potential and loses electrons easily. Similarly, between C and D, C is more reactive as it has a smaller atomic size, more electro negativity and gains electrons easily. 10. Hydrogen is kept in IA despite not being an alkali metal. Hydrogen is kept in IA despite not being an alkali metal because it is simplest and first element with one valance electron.

376 Oasis School Science and Technology - 10 Exercises 1. Choose the best answer from the given alternatives. a. What is Mendeleev’s periodic table based upon? i. atomic mass ii. atomic number ii. number of electrons iii. atomic size b. Why is hydrogen kept at the top of IA group? i. its valency is 1. ii. it loses one electron like IA group. iii. it has one electron in the outermost orbit. iv. it is the element with the least atomic number. c. The calcium belongs to the fourth period. Why? i. It has four valence electrons. ii. it has four protons and four neutrons. iii. it has four shells. iv. its atomic mass is four. d. Why does the ionization potential increase from left to the right in the periodic table? i. due to increase in the size of the atom due to additional electrons. ii. due to decrease in the size of atom due to additional protons and neutrons. iii. due to presence of additional shells. iv. due to loss of electrons. e. Reactivity of a metallic atom increases from top to bottom in the group. Why? i. due to increase in electronegativity and due to an increase in atomic size. ii. due to decrease in ionization potential and due to an increase in atomic size. iii. due to decrease in atomic size and due to an increase in nuclear charge. iv. due to increase in the number of valance electrons. f. Which one of the following is the most reactive nonmetal? i. fluorine ii. nitrogen iii. oxygen iv. neon 2. Define the following terms with required examples. a. Periodic table b. Modern periodic table c. Mendeleev’s periodic table d. Modern periodic law e. Mendeleev’s periodic law f. Isotopes g. Lanthanides h. Actinides i. Inert gases j. Alkali metals k. Halogens l. Periods m. Groups n. Atomic size

Oasis School Science and Technology - 10 377 o. Ionization potential p. Valance electron q. valency r. Electronegativity s. Aufbau principle t. Electronic configuration u. s-block elements v. p-block elements w. d-block elements x. f-block elements y. Transition metals z. Alkaline earth metals 3. Answer the following questions in very short. a. Write the electronic configuration of sodium, chlorine and potassium based on the sub-shell. b. Which element has this electronic configuration? 1s2 , 2s2 2p6 , 3s2 3p6 , 4s1 c. Which one is more reactive between Mg and Al? d. How many groups and periods are there in the modern periodic table? e. How many electrons can fit in each subshell? f. Which group do the element 1s2 , 2s2 2p5 belong to? g. What are the elements that lie in the group between IIA and IIIA called? h. In which group do inert gases belong to? i. Which block of the modern periodic table makes acidic oxides? j. Write the group of alkali metals and halogens. 4. Give reasons. a. Elements must be classified. b. Elements of IIA group are called alkaline earth metals. c. Sodium is more reactive than magnesium but less reactive than potassium. d. Inert gases are kept in the zero group. e. Lanthanides and actinides are kept separately below the main block. f. As we move from top to bottom, the reactivity of non-metals decreases. g. Potassium is kept in the s- block of the periodic table. h. Lanthanides and actinides are also called inner-transitional elements. i. As we move from top to bottom, the reactivity of metals increases. j. The reactivity of metal decreases from left to the right in the period. k. Ionization potential increases from left to right in periodic table. l. Atomic size increases down the group. m. Atomic size decrease across the period from left to right. n. Fluorine is more reactive than chlorine. o. Neon is kept in the zero group. p. Elements of IA group are called alkali metals. q. Reactivity of non-metal increases across the period from left to right. 5. Differentiate between the following. a. Modern periodic table and Mendeleev’s periodic table b. Period and group c s-block and p-block e. Alkali metals and halogens

378 Oasis School Science and Technology - 10 6. Answer the following questions in short. a. Describe in brief the position of hydrogen in the modern periodic table. b What are the characteristics of modern periodic table? c. On what basis groups and periods are classified in the modern periodic table? d. How does the reactivity of the metal vary in the group? e. How does the reactivity of metal vary in the period? f. Why do electrons jump to 4s before going to 3d? g. Write the electronic configuration of oxygen and write its position in the modern periodic table. h. Write the location of aluminium in the modern periodic table. Why is it in p-block? 7. Answer the following questions based on the given electronic configuration. A = 1s2 , 2s2 2p6 , 3s1 B = 1s2 , 2s2 2p6 , 3s2 3p5 i. Identify periods and groups of the above elements. ii. Name the above elements. iii. Which compound is formed between A and B? Write any two characteristics of this compound. 8. Answer the following long questions. a. What are the characteristics of the groups and periods? b. What are subshells? Describe its types. c. Discuss the reactivity of non-metal in groups and periods. d. In which group and period do fluorine, chlorine and bromine belong? Which one of them is most reactive? Why? e. Enlist the advantages of modern periodic table. 9. A hypothetical sequence with an electronic configuration of some elements is given below. With the help of this sequence, answer the following questions. Elements A B C D E F G H Configuration 2, 1 2, 2 2, 3 2, 4 2, 5 2, 6 2, 7 2, 8 i. Which period is shown in the table? ii. Which group E belongs to? How many orbits does it have? iii. Which of them are metals, nonmetals and inert gas? iv. What is the valency of B and G and why? v. Write the name of the most reactive metal and most reactive nonmetal from this table.

Oasis School Science and Technology - 10 379 UNIT 15 CHEMICAL REACTION Estimated teaching periods Theory 4 Practical 2 • Types of chemical reaction: composition, decomposition, displacement and acid-base reaction. • Rate of chemical reaction • Factors affecting the rate of chemical reaction(heat, pressure, catalyst, light and surface area) The Sequence of Curriculum Issued by CDC Amedeo Avogadro is well known for his contribution to the molecular theory known as Avogadro’s law. He was born in Italy on 9th August 1776 and died on 9th July 1856. He is an Italian chemist. He discovered that 1 mole of substances contains 6.02214076 ×1023 entities, known as Avogadro’s constant. About the Scientist Amedeo Avogadro Key terms and terminologies 1. Chemical reaction : The chemical change which involves the addition/ decomposition/ displacement of the atom or a group of atoms is called a chemical reaction. 2. Chemical equation : The equation in which chemical reactions are expressed using words or symbols is called a chemical equation. 3. Word equation : If the chemical change is expressed by writing the full names of reactant and product molecules, it is called the word equation. 4. Formula equation : If the chemical change is expressed by using symbols of reactant and product molecules, it is called the formula equation. 5. Reactants : The chemical substances which take part in the chemical reaction are called reactants. 6. Products : The chemical substances which are obtained after the chemical reaction are called products. 7. Exothermic reactions : Those chemical reactions which release heat to the surrounding are called exothermic reactions. 8. Endothermic reactions : Those chemical reactions which absorb heat from the surrounding are called endothermic reactions.

380 Oasis School Science and Technology - 10 9. Reversible reactions : Such types of reactions which occur both in forward and backward directions are called reversible reactions. 10. Irreversible reactions : Those chemical reactions which occur only in one direction are called irreversible reactions. 11. Unbalanced equation : The chemical equation in which the total numbers of atoms of each element in reactant and product molecules are not equal is called an unbalanced chemical equation. 12. Balanced equation : The chemical equation in which the total numbers of atoms of each element in reactant and product molecules are equal is called a balanced chemical equation. 13. Addition reactions : Those chemical reactions in which two or more atoms or groups of atoms are combined to give a single product are called addition reactions. 14. Decomposition reactions: Those chemical reactions in which a single reactant molecule is decomposed into two or more products are called decomposition reactions. 15. Displacement reactions: Those chemical reactions in which atoms or group of atoms are displaced by other atoms or group of atoms are called displacement reactions. 16. Acid-base reactions : Those chemical reactions in which acid and base react together to give salt and water are called acid-base reactions. 17. Rate of reaction : The amount of the reactant that is converted into the product per unit time is called the rate of the chemical reaction. 18. Catalysts : The chemical substances which either increase or decrease the rate of chemical reactions are called catalysts. 19. Positive catalysts : Positive catalysts increase the rate of chemical reactions. They include manganese dioxide, V2 O5 (Vanadium pentoxide) iron, nickel, copper, etc. 20. Negative catalysts : Negative catalysts decrease the rate of chemical reactions. For example, glycerine H3 PO4 (Phosphoric acid), etc. Introduction Change is the rule of nature. Every time changes are occurring in our surroundings as well as inside the body. Cloud, rain, day, night, seasons, etc. are the result of changes in the surrounding. Growth, development, happiness, sadness, etc. are the result of changes in the body. Boiling of water, cooking of food, digestion of food inside the stomach, corrosion of metals, making of different objects from soil and wood, etc. are some more changes in our surroundings. If we categorize these changes, then we can make them into two groups, namely physical change and chemical change. In a physical change, only physical properties like physical state, colour, odour, taste, etc. are changed. It is a temporary reversible change. Whereas, in a chemical change, new substances are formed. It is a permanent irreversible change. Digestion of food, corrosion of metals, burning of fuels, etc. are some examples of chemical change. In every chemical change, there occurs addition/ decomposition/ displacement of atoms or molecules of matter. Chemical Reaction Take some amount of hydrochloric acid, mix it with sodium hydroxide and observe the mixture. You will see some solid matter at the bottom of this reacting vessel. This solid

Oasis School Science and Technology - 10 381 substance is called salt. Do you know how this salt forms? Similarly, take a piece of zinc and insert it into a test tube containing some dilute sulphuric acid. Observe this mixture for some time. Do you see any change there? All these activities are called chemical reactions. In these reactions, there may be addition or decomposition or displacement of atoms or molecules of matter. Thus, the chemical change which involves the addition/ decomposition/ displacement of the atom or a group of atoms is called a chemical reaction. The chemical reactions can be expressed in words or symbols. The equation in which chemical reactions are expressed using words or symbols is called a chemical equation. It could be a word equation or a formula equation. 1. Word equation It is a very simple method to express chemical change. In this method, the full names of reactant and product molecules are written on their respective sides. So, if the chemical change is expressed by writing the full names of reactant and product molecules, it is called the word equation. Hydrogen + Oxygen Water Nitrogen + Hydrogen Ammonia Calcium carbonate D Calcium oxide + Carbon dioxide 2. Formula equation It is an easy and scientific method to express chemical change. In this method, the symbols of reactant and product molecules are written on their respective sides. So, if the chemical change is expressed by using symbols of reactant and product molecules, it is called the formula equation. 2H2 + O2 2H2 O N2 + 3H2 2NH3 CaCO3 CaO + CO2 Reactants and Products Let’s see the given chemical equation, HCI + NaOH NaCl + H2 O In this equation, hydrochloric acid and sodium hydroxide react together to give sodium chloride and water. Here, hydrochloric acid and sodium hydroxide are reactants as they are participating in the chemical reaction. Similarly, sodium chloride and water are products because they are obtained after the reaction. We write reactants on the left-hand side of an arrow and products on the right-hand side. The chemical substances which take part in the chemical reaction are called reactants and similarly, the chemical substances which are obtained after the chemical reaction are called products. HCI + NaOH NaCl + H2 O Reactants Products Exothermic and Endothermic Reactions There are so many chemical reactions which do not require heat for their initiation and completion. They occur spontaneously without any external energy. These reactions are

382 Oasis School Science and Technology - 10 called exothermic reactions. Thus, those chemical reactions which release heat to the surrounding are called exothermic reactions. C + O2 CO2 + Heat C + 2H2 CH4 + Heat CH4 + 2O2 CO2 + 2H2 O + Heat There are also some chemical reactions which do not initiate, proceed and complete without supplying external heat. They are non-spontaneous chemical reactions. These reactions are called endothermic reactions. Therefore, those chemical reactions which absorb heat from the surrounding are called endothermic reactions. 2KCIO3 D 2KCI + 3O2 CaCO3 D CaO + CO2 Reversible and irreversible reactions Let’s discuss the formation of hydrogen iodide and sodium chloride. In the formation of hydrogen iodide, hydrogen and iodine are combined together. When some amount of hydrogen iodide is produced, it undergoes decomposition to give hydrogen and iodine again. Such types of reactions which occur both in forward and backward directions are called reversible reactions. To express these reactions, we use a double-headed arrow (⇌) between reactant and product molecules. H2 + I2 2HI N2 + 3H2 2NH3 Similarly, sodium chloride is formed from sodium atom and chlorine atom. When sodium chloride is formed, the formation of sodium and chlorine does not occur again. These types of reactions occur only in the forward direction. To express them, we use a single-way arrow (→) between reactant and product molecules. Those chemical reactions which occur only in one direction are called irreversible reactions. CaCO3 CaO + CO2 2H2 O2 2H2 O + O2 Unbalanced chemical equation To write a chemical reaction, we write an unbalanced/skeletal equation first. In this reaction, the total numbers of atoms of each element in reactant and product molecules are not equal. So, the chemical equation in which the total numbers of atoms of each element in reactant and product molecules are not equal is called an unbalanced chemical equation. KCIO3 KCI + O2 N2 + H2 NH3 Balanced chemical equation To overcome the defects of an unbalanced chemical equation and to make it more informative, an unbalanced/skeletal equation is balanced by giving a suitable coefficient.

Oasis School Science and Technology - 10 383 In this equation, the atoms of each element in the reactant and product molecules are the same. The chemical equation in which the total numbers of atoms of each element in reactant and product molecules are equal is called a balanced chemical equation. 2KCIO3 2KCI + 3O2 N2 + 3H2 2NH3 Some examples of balanced chemical equations 1. Nitrogen + Hydrogen Ammonia (word equation) N2 + H2 NH3 (skeletal equation) N2 + 3H2 2NH3 (balanced equation) 2. Iron + Oxygen Ferric oxide (word equation) Fe + O2 Fe2 O3 (skeletal equation) 4Fe + 3O2 2Fe2 O3 (balanced equation) 3. Phosphorus + Oxygen Phosphorus pentoxide (word equation) P + O2 P2 O5 (skeletal equation) 4P + 5O2 2P2 O5 (balanced equation) Types of Chemical Reactions There are several types of chemical reactions; among them, four basic types of chemical reactions are discussed below: 1. Addition (or Combination or Synthesis) reaction Formation of water from hydrogen and oxygen, formation of carbon dioxide from carbon and oxygen, formation of ammonia from nitrogen and hydrogen, etc. are some examples of addition reactions. In these reactions, two or more atoms are combined to give a single product. Those chemical reactions in which two or more atoms or groups of atoms are combined to give a single product are called addition reactions. For example: 2Na + Cl2 2NaCl 2H2 + O2 2H2 O N2 + 3H2 2NH3 C + O2 CO2 S + O2 SO2 2. Decomposition reaction When calcium carbonate is heated at high temperatures, it gives calcium oxide and carbon dioxide. In this reaction, a single reactant molecule (i.e. calcium carbonate) is converted into two products (i.e. calcium oxide and carbon dioxide). Such types of reactions are called decomposition reactions.

384 Oasis School Science and Technology - 10 The chemical reactions in which a single reactant molecule is decomposed into two or more products are called decomposition reactions. For example: CaCO3 CaO + CO2 2KClO3 2KCI + 3O2 2H2 O2 2 H2 O + O2 CuCO3 CuO + CO2 2Pb(NO3 )2 2PbO + 4NO2 + O2 3. Displacement reaction Put a piece of zinc in a test tube containing dilute sulphuric acid. It starts to evolve hydrogen gas and makes zinc sulphate. In this reaction, hydrogen is a chemical reaction displaced by zinc from sulphuric acid. Such types of reactions where atoms or molecules are displaced by others are called displacement reactions. The chemical reactions in which atoms or group of atoms are displaced by other atoms or group of atoms are called displacement reactions. There are two types of displacement reactions. a. Single displacement reaction b. Double displacement reaction a. Single displacement reaction In this type of chemical reaction, one atom or one group of atoms is displaced by another atom or group of atoms. For example Zn + H2 SO4 ZnSO4 + H2 Fe + CuSO4 FeSO4 + Cu Mg + 2HCI MgCl2 + H2 2KI + CI2 2KCI + I2 b. Double displacement reaction In this type of chemical reaction, both the reactant molecules are decomposed into opposite ions and give new products after exchanging corresponding opposite ions. For example NaCl + AgNO3 NaNO3 + AgCl CaCl2 + 2AgNO3 Ca(NO3 )2 + 2AgCl Na2 CO3 + MgCl2 2NaCl + MgCO3 Pb (NO3 ) 2 + Na2 SO4 PbSO4 + 2NaNO3

Oasis School Science and Technology - 10 385 4. Acid-base or neutralization reaction Take a test tube and put some amount of hydrochloric acid and sodium hydroxide. After their reaction, we will get sodium chloride and water. This is an acid-base reaction. As a result of this reaction, acid and base lose their own properties; hence it is also called a neutralization reaction. Those chemical reactions in which acid and base react together to give salt and water are called acid-base reactions. For example Acid + Base Salt + Water HCI + NaOH NaCl + H2 O H2 SO4 + KOH K2 SO4 + H2 O 2HNO3 + Ca(OH)2 Ca(NO3 )2 + 2H2 O Reasonable Fact An acid-base reaction also called a neutralization reaction. In an acid-base reaction, both acid and base lose their properties during the chemical reaction. As a result, a neutral substance (i.e., salt and water) is formed. So, the acid-base reaction is also called the neutralization reaction. Rate of Chemical Reaction Let’s take a piece of zinc and put it in the test tube containing dilute sulphuric acid. Zinc starts to dissolve in acid. The bubbles of hydrogen gas start to form in the test tube. It is a very fast chemical reaction. Similarly, put a piece of iron rod in the open air. It takes some days to be rusted. It is a very slow chemical reaction. So, the rate of chemical reaction differs for different substances. It also depends upon several external factors like heat, light, catalyst, pressure, electricity, etc. The rate of the reaction is determined by calculating the amount of the reactant that is converted into a product in the given period. The amount of the reactant that is converted into the product per unit time is called the rate of the chemical reaction. To increase the rate of the chemical reaction, we can increase the rate of the reactant molecules. This is because the rate of most of the chemical reactions increases with increasing temperature. The catalyst also increases the rate of the chemical reaction. Factors affecting the rate of the chemical reaction. There are many factors which affect the rate of chemical reaction; among them, some important factors are described below. a. Heat Heat is a form of energy which supplies kinetic energy to the reacting molecules. When heat is absorbed, the vibration of reacting molecules increases increasing the frequency of collision. So, the more heat the more collision and more products.

386 Oasis School Science and Technology - 10 For example; when we supply heat, the decomposition of calcium carbonate and potassium chloride becomes fast. CaCO3 CaO + CO2 2KClO3 2KCl + 3O2 b. Light There are certain chemical reactions which occur in the presence of sunlight. Not only this but there are also some reactions which are initiated in the presence of sunlight only. They include photosynthesis in plants, chlorination in alkanes, decomposition of silver bromide, etc. H2 + Cl2 light 2HCl CH4 + Cl2 light CH3 Cl+ HCl 2AgBr light 2Ag + Br2 6CO2 + 6H2 O light, chlorophyll 6C6 H12O6 + 6O2 c. Pressure Pressure is a factor which decreases the volume of reacting molecules. As a result of this, reactant molecules come close to each other and collide easily. So, if the volume of reactant molecules is more than product molecules, we should supply pressure to accelerate the rate of reaction. For example, the formation of ammonia from nitrogen and hydrogen takes place in the presence of 200 to 500 atmospheric pressure. N2 + 3H2 200 to 500 atm/500°C/ Fe, Mo 2NH3 d. Catalysts The decomposition of hydrogen peroxide increases in the presence of manganese dioxide and decreases in the presence of glycerine. Here, manganese dioxide and glycerine are called catalysts. So, the chemical substances which either increase or decrease the rate of chemical reactions are called catalysts. There are two types of catalysts. i) Positive catalysts ii) Negative catalysts i) Positive catalysts They increase the rate of chemical reactions. They include manganese dioxide, V2 O5 (Vanadium pentoxide) iron, nickel, copper, etc. N2 + 3H2 Fe,Mo 2NH3

Oasis School Science and Technology - 10 387 2H2 O2 MnO2 2H2 O + O2 2KClO3 MnO2 2KCl + 3O2 Reasonable Fact Manganese dioxide (MnO2 ) is called a positive catalyst. Manganese dioxide (MnO2 ) increases the rate of the chemical reaction. So, it is called a positive catalyst. ii) Negative catalysts They decrease the rate of chemical reactions. For example, glycerine H3 PO4 (Phosphoric acid), etc. 2H2 O2 Glycerine 2H2 + O2 e. Electricity During the process of electrolysis of water, we supply the electricity in acidified water. As a result, we get hydrogen and oxygen gases at their respective electrodes. Similar types of many reactions occur in the presence of electricity. 2H2 O electrolyte/electricity 2H2 + O2 f. Solution When silver nitrate and sodium chloride are mixed, they do not give any product. But when they are mixed in water, they react together and give silver chloride and sodium nitrate. This experiment shows that solution is a factor to initiate, accelerate and complete the chemical reaction. For example, AgNO3 (aq) + NaCl(aq) AgCl (s) + NaNO3 (aq) g. Contact Contact is the main and prime factor to initiate a chemical reaction. So, if there is no contact, there is no reaction and there is no product. For example, when sodium metal comes in contact with chlorine non-metal, it gives sodium chloride. 2Na + Cl2 2NaCl Reasonable Fact The rate of a chemical reaction increases with increasing the concentration of reactants. The rate of a chemical reaction increases with increasing the concentration of reactants. It is because increasing the concentration of reactants increases the number of reacting molecules. There will be more collision between the reacting molecules and hence the rate of chemical reaction increases. h. Surface area The surface area plays a very important in the rate of reaction. If reactants have a greater surface area, more molecules come in contact and increase the rate of the chemical reaction and vice versa. Fact File Tablet of vitamin C dissolves slower than the powder of vitamin C tablet.

388 Oasis School Science and Technology - 10 Reasonable Thinking Skill Reasonable Thinking Skill R T S 1. A reaction between hydrochloric acid and sodium hydroxide is called a neutralization reaction. Give reason along with a chemical equation. A reaction between hydrochloric acid and sodium hydroxide is called a neutralization reaction because whenever these two reactants react, they produce neutral substances such as salt (sodium chloride) and water. Hydrochloric acid + Sodium hydroxide → Sodium chloride + Water HCl + NaOH → NaCl + H2 O 3. When glycerine was added to hydrogen peroxide the rate of production of oxygen slowed down. What is the role of glycerine in this chemical change? Does it take part in a chemical reaction? When glycerine was added to hydrogen peroxide, the rate of production of oxygen slowed down. Since glycerine itself does not take part in chemical reactions but the rate of reaction has slowed down, the role of glycerine here is a negative catalyst. No! the glycerine won’t take part in a chemical reaction when added to hydrogen peroxide. 4. Powder sodium chloride does not react with powder sliver nitrate but they react when water is added to them. Powder sodium chloride does not react with powder silver nitrate but it can easily react when water is added to it. The reason is the solution state of the reactant. When the sodium chloride and silver nitrate are mixed with water, they will change into a solution. They will ionize and produce radicals. More molecules will come in contact and the reaction will occur faster. 5. Reaction between nitrogen and hydrogen to produce ammonia is a reversible reaction. The reaction between nitrogen and hydrogen to produce ammonia is a reversible reaction because they combine to form ammonia, which can instantly decompose to produce hydrogen and nitrogen. N2 + 3H2 ⇌ 2NH3 2NH3 ⇌ N2 + 3H2 8. Carbon dioxide is a fire extinguisher. What happens if a burning magnesium is put in a gas jar full of carbon dioxide? Write a balanced chemical equation and mention the type of reaction. Carbon dioxide does not support burning. It is a fire extinguisher. But if burning magnesium is put in a gas jar full of carbon dioxide, the fire won’t go out. The magnesium ribbon keeps burning by replacing carbon from carbon dioxide. As a result, a white powder of magnesium oxide and black particles of carbon are formed. Above chemical reaction is represented as: Word equation : Magnesium + Carbon dioxide → Magnesium oxide + Carbon Unbalanced equation : Mg + CO2 → MgO + C Balanced equation : 2Mg + CO2 → 2MgO + C The above reaction between burning magnesium ribbon and carbon dioxide is a displacement reaction.

Oasis School Science and Technology - 10 389 9. What happens when, an iron nail is placed in a blue vitrol (copper sulphate) solution for a few days? What type of reaction is it? Write a balanced chemical equation for the reaction. Since iron is more reactive than copper, iron displaces copper from copper sulphate to produce iron sulphate. Word equation : Copper sulphate + Iron → Iron sulphate + Copper Balanced equation : CuSO4 + Fe → FeSO4 + Cu So, when an iron nail is placed in blue vitrol solution for a few days, the iron nail starts to lose iron molecules continuously and copper molecules fill those eroded places. After a few days, the iron nail will change into a copper nail due to a continuous displacement reaction. 10. What happens when limestone is heated at a higher temperature in a coal furnace? Mention the type of reaction. When limestone is heated at a higher temperature it absorbs heat and breaks down to produce calcium oxide and carbon dioxide. Limestone D Calcium oxide + Carbon dioxide CaCO3 D CaO + CO2 The reaction where limestone is heated to form calcium oxide and carbon dioxide is a decomposition reaction. Exercises 1. Choose the best answer from the given alternatives. a. Which of the following are reactants in the given equation? HCl + NaOH → NaCl + H2 O i. HCl ii. NaCl iii. HCl and NaOH iv. H2 O b. What does this symbol (⇌) represent? i. endothermic reaction ii. exothermic reaction iii. reversible reaction iv. irreversible reaction c. Which one of the following is a combination reaction? i. 2Na + Cl2 → 2 NaCl ii. CaCO3 → CaO + CO2 iii. HCl + NaOH → NaCl + H2 O iv. Na+ + e– → Na d. How does heat affect the chemical reaction? i. by decreasing the vibrations of the molecules ii. by increasing the kinetic energy of the molecules iii. by passing electricity into the reactants iv. heat increases pressure in the reactants

390 Oasis School Science and Technology - 10 e. What is the type of this reaction?HCl + NaOH → NaCl + H2 O i. addition ii. decomposition iii. displacement iv. acid-base 2. Define the following terms with required examples. a. Chemical reaction b. Balanced equation c. Combination reactions d. Decomposition reactions e. Displacement reactions f. Single displacement reactions g. Double displacement rections h. Acid-base reactions i. Rate of chemical reactions j. Catalyst k. Positive catalyst l. Negative catalyst 3. Answer the following questions in very short. a. Balance the given equation. H2 + O2 → H2 O b. Identify the type of reaction. Write the names of reactants and products. Fe + CuSO4 → FeSO4 + Cu c. What is the type of reaction if sodium chloride reacts with lead nitrate? d. What are the four factors that affect the rate of a chemical reaction? e. What is the role of glycerine while preparing oxygen from decomposition of hydrogen peroxide? 4. Give reasons. a. Addition reaction is also known as a synthesis reaction. b. Acid-base reaction is also known as neutralization reaction. c. Rusting of iron is a chemical change. d. Heating of calcium carbonate is called an irreversible reaction. e. Acid-base reaction is an exothermic reaction. f. Manganese dioxide is added to hydrogen peroxide while producing oxygen. g. Formation of table salt from sodium and chlorine is called an addition reaction. h. Heating can accelerate the chemical reaction. i. Silver chloride, silver nitrate, hydrogen peroxide etc. cannot be stored in a transparent bottle. j. When we consume lots of pineapples, teeth will be corroded. 5. Differentiate between the following. a. reversible reaction and irreversible reaction b. balanced chemical equation and unbalanced chemical equation c. Single displacement reaction and double displacement reaction

Oasis School Science and Technology - 10 391 6. Answer the following questions in short. a. Explain a double displacement reaction with an example. b. How does the catalyst affect the chemical reaction? Explain with an example. c. Write the balanced chemical equation for the reaction between sodium and chlorine. Mention the type of reaction. d. Give an example of a single displacement reaction and double displacement reaction and balance it. e. Give an example of each combination reaction and decomposition reaction. f. What happens to the rate of chemical reaction, when yeast is added to the hydrogen peroxide? g. Why does the water rise in the glass, when a burning candle, on a plate with water is covered by the inverted glass? 7. Answer the following long questions. a. What information is obtained from balanced chemical equations? b. What factors affect the chemical reaction? Enlist and describe each of them. c. How does pressure affect the chemical reaction? Explain with an example. d. Write the name of reactant X in the given chemical equation. Na + X → Na2 O. Complete the reaction and balance it. e. Observe the given chemical reaction and answer the following question. Calcium carbonate D Calcium oxide + Carbon dioxide i. Write the names of reactants and products. ii. Mention the type of reaction. iii. What does the triangle represent? 8. Some word equations are given below. Translate these word equations into a balanced formula equation. Also, mention their type. a. Iron + Oxygen → Iron oxide b. Potassium chlorate → Potassium chloride + Oxygen c. Zinc + Sulphuric acid → Zinc sulphate + Hydrogen d. Calcium chloride + Silver nitrate → Silver chloride + Sodium nitrate e. Sulphuric acid + Sodium hydroxide→ Sodium sulphate + Water f. Ammonium chloride + Calcium hydroxide → Calcium chloride +Ammonia + Water g. Lead nitrate → Lead oxide + Nitrogen dioxide + Oxygen h. Methane + Oxygen → Carbon dioxide +Water

392 Oasis School Science and Technology - 10 UNIT 16 SOME GASES Estimated teaching periods Theory 5 Practical 3 • Laboratory preparation of carbon dioxide and ammonia gases • Physical properties, chemical properties and application • Greenhouse effect: causes, effects and control measures • Acid rain: causes (reaction of carbon dioxide and sulphur dioxide with water to produce respective acid) • Effects and control measures The Sequence of Curriculum Issued by CDC Fritz Haber is well known for developing the Haber-Bosch process to synthesize ammonia from nitrogen and hydrogen. He was born in Prussia (now Poland) on 9th December 1868 and died on 29th January 1934. He was a chemist who is known for surface chemistry, the Haber process, Haber’s rule, explosives and fertilizer. He synthesised urea that could be used as fertilizer. He was honoured with the Iron cross, Nobel Prize in Chemistry etc. About the Scientist Fritz Haber Key terms and terminologies 1. Laboratory preparation of CO2 : In the laboratory, carbon dioxide gas can be prepared by the reaction of dilute hydrochloric acid with calcium carbonate (or marble or limestone). 2. Dry ice : The solid form of carbon dioxide gas which is obtained by cooling it below -78°C is called dry ice. 3. Laboratory preparation of NH3 : In a laboratory, ammonia gas can be prepared by heating a mixture of ammonium chloride (NH4 Cl) and calcium hydroxide {Ca(OH)2 } in a ratio of 2:1. 4. Greenhouse : A natural or artificial set-up that can trap heat energy and regulate the temperature of a particular place keeping greenery of the plants is called a greenhouse. 5. Greenhouse effect : The phenomenon of increasing the temperature of the earth as in an artificial greenhouse is called the greenhouse effect. 6. Greenhouse gases : The gases which are responsible for the greenhouse effect are called greenhouse gases.

Oasis School Science and Technology - 10 393 7. Artificial greenhouse : Artificial greenhouse is a structure with walls and roofs made chiefly of transparent materials such as glass or plastics in which plants requiring regulated climatic conditions are grown. 8. Cold frame : A miniature greenhouse is known as a cold frame. 9. Acid rain : The rain that contains a small volume of acids formed by chemical reactions between rain and industrial gases is called acid rain. Introduction to Carbon dioxide Gas Lavoisier discovered that carbon dioxide is a compound gas of one carbon and two oxygen atoms in 1755. The molecular formula of carbon dioxide is CO2 , and its molecular weight is 44. It is found in a free as well as a combined state in nature. In the atmosphere, the volume of carbon dioxide gas is about 0.03%. It is heavier than air, so it is present at the lower level of the atmosphere like deep wells, mines, caves, etc. The main sources of carbon dioxide are burning of carbon-containing fuel, respiration of living beings, fermentation of organic matter, volcanic eruption and exhaust of vehicles. Carbon dioxide has great importance in the existence of life on the earth. Green plants transfer solar energy into chemical energy with the help of the photosynthesis process. In this process, they use carbon dioxide and water in the presence of sunlight. It was discovered in 1630 By Van Helmont from fire. It was prepared by Joseph Black by heating magnesium carbonate. Compound Carbon dioxide Molecular formula CO2 Molecular weight 44 Colour Colourless Odour Faint acidic smell Nature Acidic O C O Fig: molecular structure of carbon dioxide General methods of preparation of carbon dioxide gas 1. By the combustion of carbon-containing compounds We can prepare carbon dioxide gas by the combustion of carbonic compounds like methane, ethane, carbohydrates, etc. CH4 + 2O2 CO2 + 2H2 O

394 Oasis School Science and Technology - 10 C6 H12O6 + 6O2 6CO2 + 6H2 O 2. By the reaction of the acid with carbonates and bicarbonates The acid reacts with carbonates and bicarbonates of different types of metals to give carbon dioxide gas. CaCO3 + 2HCl CaCl2 + H2 O + CO2 Ca(HCO3 )2 + 2HCl CaCl2 + 2H2 O + 2CO2 Laboratory Preparation of Carbon dioxide Gas Principle In the laboratory, carbon dioxide gas can be prepared by the reaction of dilute hydrochloric acid with calcium carbonate (or marble or limestone). CaCO3 + 2HCl CaCl2 + H2 O + CO2 Apparatus required i. Woulfe's bottle ii. Thistle funnel iii. Gas jar iv. Delivery tube Chemicals required Calcium carbonate or limestone or marble (CaCO3 ) Dilute hydrochloric acid (HCI) Dilute hydrochloric acid Delivery tube Carbon dioxide Moist blue litmus paper Gas jar Thistle funnel Cork Woulfe's bottle Lime stone pieces Fig. Laboratory preparation of carbon dioxide Procedure 1. Take a Woulfe’s bottle and put a few pieces of marble chips inside it. 2. The apparatus arrangement should be made according to the above figure. 3. Pour dilute hydrochloric acid with the help of a thistle funnel till it covers the marble chips and the lower end of the thistle funnel. 4. As soon as marble chips come in contact with acid, a reaction takes place with brisk effervescence.

Oasis School Science and Technology - 10 395 5. Now, carbon dioxide gas is produced within Woulfe’s bottle. This gas is collected in a gas jar with the upward displacement of air, passing through the delivery tube. Reasonable Fact We should not use dilute sulphuric acid instead of dilute hydrochloric acid during laboratory preparation of carbon dioxide. Dilute sulphuric acid forms calcium sulphate when it reacts with calcium carbonate. This calcium sulphate covers the remaining part of the marble and does not allow further reaction. Hence, we do not use dilute sulphuric acid in place of dilute hydrochloric acid. Precautions i. Woulfe's bottle should be airtight. ii. The lower end of a thistle funnel should be dipped in the solution. iii. The end of the delivery tube should not touch the solution. iv. Carbon dioxide gas should be collected by upward displacement of air. Reasonable Fact The lower end of the thistle funnel should be dipped in the solution. The lower end of the thistle funnel should be dipped in the solution to prevent carbon dioxide gas from escaping from the thistle funnel. Test of Carbon dioxide Gas 1. We know that carbon dioxide is a non-combustible gas. It also does not support combustion. So, to test it, take a burning candle near the mouth of a gas jar. If a burning candle is extinguished, it confirms that it is carbon dioxide gas. 2. We already discussed that carbon dioxide is an acidic gas, so it turns moist blue litmus paper into red. 3. Carbon dioxide turns lime water milky white when it is passed through it for a short duration. The milky white colour is due to the formation of insoluble calcium carbonate (CaCO3 ). Carbon dioxide + Calcium hydroxide Calcium carbonate + Water CO2 + Ca(OH)2 CaCO3 + H2 O When carbon dioxide is allowed to pass for a long duration then it produces soluble calcium bicarbonate. As a result, the milky white colour disappears. Calcium carbonate + Water + Carbon dioxide Calcium bicarbonate CaCO3 + H2 O + CO2 Ca (HCO3 )2 Manufacture of carbon dioxide gas There are several uses for carbon dioxide gas. So, it is necessary to produce it on a large scale. For the commercial manufacturing of carbon dioxide gas, calcium carbonate (or limestone or marble) is heated strongly. As a result, carbon dioxide gas along with quick Fact File 1. Carbon dioxide is heavier than air, so it is collected by the upward displacement of air. 2. Carbon dioxide is a non-combustible gas, so it is used as a fire extinguisher.

396 Oasis School Science and Technology - 10 lime (or calcium oxide) is produced. Now, it is collected and used for different purposes. CaCO3 D CaO + CO2 Properties of carbon dioxide gas Physical properties of carbon dioxide i. Carbon dioxide is colourless, odourless with a faint acidic taste and smell. ii. It is quite soluble in water to produce carbonic acid (H2 CO3 ). iii. It is acidic. So, it turns blue litmus paper into red. iv. It is non-combustible gas and also does not support combustion. v. It is 1.5 times as heavy as air, so it is present in deep wells, mines, etc. vi. It can change into snow-like dry ice at -78°C. The solid form of carbon dioxide gas which is obtained by cooling it below -78°C is called dry ice. It melts without wetting the papers and clothes. So, it is also called dry ice. Chemical Properties of Carbon dioxide 1. Reaction with water When carbon dioxide gas is passed through water, it gives carbonic acid (H2 CO3 ). Carbon dioxide + Water Carbonic acid CO2 + H2 O H2 CO3 2. Reaction with ammonia When carbon dioxide reacts with ammonia gas, it gives urea, which is used as a fertilizer. Carbon dioxide + Ammonia Urea + Water CO2 + 2NH3 NH2 - CO - NH2 + H2 O 3. Reaction with magnesium Burning magnesium ribbon burns with carbon dioxide to produce magnesium oxide and carbon. Carbon dioxide + Magnesium Magnesium oxide + Carbon CO2 + 2Mg 2MgO + C 4. Reaction with alkali When carbon dioxide reacts with an alkaline solution of sodium hydroxide, it gives sodium carbonate and water. Carbon dioxide + Sodium hydroxide Sodium carbonate + Water CO2 + 2NaOH Na2 CO3 + H2 O Fact File Carbon dioxide is highly soluble in water to give carbonic acid. So, we do not collect it by passing through water. Fact File During the manufacture of soda water, carbon dioxide is dissolved in water at high pressure. As we open the lid of a bottle, pressure decreases and CO2 comes out in form of bubbles.

Oasis School Science and Technology - 10 397 5. Reaction with lime water When carbon dioxide reacts with lime water, it produces insoluble calcium carbonate. Carbon dioxide + Calcium hydroxide Calcium carbonate + Water CO2 + Ca(OH)2 CaCO3 ↓ + H2 O As we pass more amount of carbon dioxide gas through this solution soluble calcium bicarbonate is obtained. Calcium carbonate + Water + Carbon dioxide Calcium bicarbonate CaCO3 + H2 O + CO2 Ca (HCO3 )2 6. Photochemical reaction Green plants use carbon dioxide gas for the process of photosynthesis. In the presence of carbon dioxide, sunlight and water, they produce carbohydrates (glucose). Carbon dioxide + Water sunlight / chlorophyll Glucose + Oxygen 6CO2 + 6H2 O sunlight / chlorophyll C6 H12O6 + 6O2 7. Reaction with carbon When carbon dioxide is heated with red hot coke at 900°C, it changes into carbon monoxide. CO2 + C 900°C 2CO Uses i. A solid form of carbon dioxide (i.e. dry ice) is used as a cooling agent in the refrigerator. ii. It is used in aerated drinks like soda water, Coca-Cola, beer, etc. iii. It is used to make carbogen. iii. It is used to manufacture fertilizers like urea (NH2 CONH2 ). iv. Green plants use carbon dioxide for the photosynthesis process. v. In the sugar industry, carbon dioxide is used to purify sugarcane juice and kill insects. vi. It is used to make sodium carbonate and baking powder. vii. Carbon dioxide is used in fire extinguishers as it does not support combustion. Reasonable Fact Carbon dioxide can be used to put out the fire. Carbon dioxide covers the burning flame making itself just like a blanket. As a result, it does not allow oxygen to enter and finally puts out the fire. Fact File Carbogen is a mixture of 5% carbon dioxide and 95% oxygen. It is used for artificial respiration for corona patients, pneumonia patients etc. Fact File Dry ice is used in refrigerators to preserve foods, fruits, vegetables and meat.

398 Oasis School Science and Technology - 10 The Working Mechanism of a Fire Extinguisher A fire extinguisher is a red-coloured metallic cylinder, which has two sections inside it. The outer section is covered by a metallic cover containing a saturated solution of sodium bicarbonate (or baking soda). The innermost section is made by a glass vessel containing a concentrated solution of sulphuric acid. This glass vessel can break easily when the knob is pressed inside. As a result, the glass vessel gets broken and acid comes out. Now, sulphuric acid gets mixed with sodium carbonate and produces carbon dioxide. This produces carbon dioxide that comes out from the nozzle to extinguish the fire. The carbon dioxide will cover the fire and prevent oxygen from reaching it. Then the fire will burn out. 2NaHCO3 + H2 SO4 Na2 SO4 + 2H2 O + 2CO2 Ammonia Ammonia is a compound gas consisting of one nitrogen and three hydrogen atoms. Its molecular formula is NH3 and its molecular weight is 17. A very small quantity of ammonia is present in the surroundings. The sharp pungent smell of ammonia can be felt near a decaying heap of organic matter or a toilet. Most of the ammonia gas is present in a combined state with different chemicals. It is highly soluble in water, so, during rainy seasons, ammonia dissolves in rainwater and is mixed with soil. It is used in manufacturing chemical fertilizers, nitric acid, plastics, dyes, fibres, etc. Compound Ammonia Molecular formula NH3 Molecular weight 17 Colour Colourless odour Pungent smell Nature Basic General methods of preparation of ammonia gas Ammonia was first prepared by heating salammoniac (ammonium chloride) and lime (calcium hydroxide). Knob Nozzle for gas Metallic cylinder solution Concentrated H2 SO4 Saturated sodium bicarbonate Fig: fire extinguisher p+ = 1 n0 = 0 p+ = 7 n0 = 7 p+ = 1 n0 = 0 p+ = 1 n0 = 0 Molecular structure of ammonia (NH3 ) H H H N

Oasis School Science and Technology - 10 399 1. By the decomposition of ammonium salts Ammonium salts like ammonium chloride (NH4 CI), ammonium sulphate{(NH4 )2 SO4 }, ammonium carbonate{(NH4 )2 CO3 }, etc. give ammonia gas after heating. Ammonium carbonate D Ammonia + Carbon dioxide + Water (NH4 ) 2 CO3 D 2NH3 ↑ + CO2 + H2 O Ammonium sulphate D Ammonia + Sulphuric acid (NH4 )2 SO4 D 2NH3 ↑ + H2 SO4 2. By the reaction of ammonium salts with a strong base When ammonium salts like ammonium chloride (NH4 CI), ammonium sulphate {(NH4 )2 SO4 }, ammonium carbonate {(NH4 )2 CO3 ), etc. react with strong bases result, like sodium hydroxide (NaOH), potassium hydroxide (KOH), etc. they give ammonia gas. NH4 Cl + KOH KCl + H2 O + NH3 (NH)2 SO4 + 2NaOH Na2 SO4 + 2H2 O + 2NH3 Laboratory Preparation of Ammonia Gas Principle In a laboratory, ammonia gas can be prepared by heating a mixture of ammonium chloride (NH4 Cl) and calcium hydroxide {Ca(OH)2 } in a ratio of 2:1. 2NH4 Cl + Ca(OH)2 CaCl2 + 2H2 O + 2NH3 Apparatus required i) Hard glass test tube ii) Delivery tube iii) Gas Jar iv) Bunsen burner/ lamp v) Stand vi) Red litmus paper Chemicals required i) Ammonium chloride (NH4 Cl) ii) Calcium hydroxide (Ca(OH)2 ) Mixture of Ca(OH)2 and NH4 Cl Ammonia gas Lime tower CaO Burner Stand Stand Fig. Laboratory preparation of ammonia gas

400 Oasis School Science and Technology - 10 Procedure 1. A mixture of ammonium chloride and calcium hydroxide is prepared in the ratio of 2:1, directly in a hard glass test tube or made outside and put in it. 2. The arrangement of the apparatus is done as shown in the figure above. 3. Heat is supplied with the help of a Bunsen burner or any other sources. 4. When both chemicals react together, they produce ammonia gas, which is delivered through a delivery tube. The gas is passed through the lime tower to remove moisture. Gas is collected in a gas jar by the downward displacement of air. Reasonable Fact A lime tower is used during the laboratory preparation of ammonia gas. Lime or calcium oxide (CaO) absorbs the moisture from ammonia gas. As a result, we get pure and dry ammonia gas while passing it through a lime tower. Precautions i. The hard glass test tube should be made airtight and slightly inclined towards its mouth. ii. Ammonia gas is collected by the downward displacement of air as it is lighter than air. iii. Uniform heat should be supplied. iv. The source of heat should be removed when ammonia gas starts to evolve. v. We should not take the ammonia smell deeply. vi. Ammonia gas should be passed through the lime tower so that calcium oxide can absorb moisture and we can obtain dry ammonia. Test of ammonia gas 1. Ammonia is a basic gas. So, it turns moist red litmus paper into blue when it is brought near the mouth of a hard glass test tube. 2. It forms white fumes of ammonium chloride (NH4 CI) when a glass rod dipped in hydrochloric acid (HCI) is brought into contact with this gas. 3. We can identify ammonia gas as it has a pungent smell. Reasonable Fact We bring moist red litmus paper near the mouth of the gas jar. We bring moist red litmus paper near the mouth of the gas jar to test whether the gas jar is filled with ammonia or not. Since ammonia is basic in nature, it turns moist red litmus paper blue. Ammonia is not collected by the downward displacement of water similar to hydrogen and oxygen. Ammonia is not collected by the downward displacement of water similar to hydrogen and oxygen because it is highly soluble in water and gives ammonium hydroxide. NH3 + H2 O → NH4 OH (Ammonium hydroxide) Fact File Ammonia gas is collected in an inverted gas jar as it is lighter than air. It changes red litmus paper into blue as it is basic.