Matter 1.1 & 1.2

Chemistry

Lecture

Chapter 1
MATTER

lecture tutorial Lab
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Today lecture

Introduction

⚫Matter
Anything that occupies space and has mass.
e.g; air, water, animals, trees, atoms, …..

⚫Matter may consists of atoms, molecules or ions.

Three States of Matter

matter 4

Chapter 1 : MATTER

1.1 Atoms and Molecules
1.2 Mole Concept
1.3 Stoichiometry (next lecture)

matter 5

1.1 Atoms and Molecules

Learning Outcome

At the end of this lecture, students should be able :
a) Write isotopic notation.
b) Interpret mass spectrum.

matter 6

1.1 Atoms and Molecules

Terms

Atom
⚫An atom is the smallest / basic unit of a chemical
element/compound.

Example: Na, Li ,Ne

Molecule
⚫ A unit consist of two or more atoms that are
chemically bonded together
⚫There are two types;
⚫ diatomic molecule : Cl2, F2, HCl, O2
⚫ polyatomic molecule : H2O, CO3

Element
⚫A substance that cannot be separated into
simpler substances by chemical means.
⚫Element consist of only one kind of atom.
⚫Element can exist as atom or molecule.

Example: Na, Li, F2, Ne, Cl2

matter 8

ACTIVITY – 1 9

Categorize the followings:
F2, NaSO4, O2, CO, Li, and CO2 as;

ATOM : Li
MOLECULE: F2, NaSO4, O2, CO, CO2
ELEMENT : Li, F2, O2
COMPOUNDS : NaSO4, CO, CO2

matter

Subatomic particles

An atom is made up,

Proton (p+) Packed in a small nucleus

Neutron (no)

Electron (e–) Move rapidly around the nucleus of

an atom

Atom is
e- electrically

neutral

8/2/2021 matter 10

1.1-15

Elements are arranged in the
order of proton number
in the periodic table

What is proton number?

PROTON NUMBER (Z)

Also known as atomic number
Number of protons in the nucleus of each atom.
In neutral atom,
number of protons = number of electrons

EXAMPLE:

11
88
11 11
18 18

NUCLEON NUMBER (A)

Nucleon number also known as mass number

Total number of protons and neutrons
present in the nucleus of an atom.

Nucleon number = Proton Number + Number of Neutrons
(A) (Z) (N)

A = 13 A = 90 A = 61

Isotopes

⚫Are atoms of the same element , having the
same number of protons but different number of
neutrons in their nucleus.

1 H 12H 3200 Hg
1 1 H80

U235 U238
92 92

⚫Are atoms of the same element , having the 14
same protons number but different nucleon
number.

matter

Isotope Notation,AZ X

• An atom can be represented by an isotope notation
( atomic symbol )

A = Nucleon element
Number of X symbol

= Z+n

Z = Proton Number 15
of X

=p

Note : X can be atom or ion

matter

EXAMPLE:

35 Cl
17

Number of protons = proton number (Z) = 17

Number of electrons = 17

Number of neutrons = 35 - 17 = 18

Nucleon number (A)
= number of protons + number of neutrons

= 17 + 18 = 35

EXAMPLE – 1

Indicate the number of protons, neutrons, and
electrons in each of the following species:

157N 1363S 2694Cu 3884Sr
15360Ba 17846W 28002Hg

Ans: EXAMPLE – 01

157N 5 17 – 5 = 12 5
1363S
16 33 – 16 = 17 16
2694Cu
3884Sr 29 64 – 29 = 35 29
20820 Hg
13506 Ba 38 64 – 29 = 35 38
18764 W
80 202 – 80 = 122 80

56 130 – 56 = 74 56

74 186 – 74 = 112 74

X A isotope notation
Z

Z=6 Z = 40 Z = 28
A=6+7
A = 40 + 50 A = 28 + 33
= 13 = 90 = 61

13 C 4900Zr 2681Ni
6

ION

⚫Atom or group of atoms that has positive or
negative charge.

Cation Anion
a positive charge ion a negative charge ion
formed when a neutral formed when a neutral
atom loses an electron(s). atom gains an electron(s).

Na Na+ Cl Cl-

11 protons 11 protons 17 protons 17 protons
11 electrons 10 electrons 17 electrons 18 electrons

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EXAMPLE – 4

Give the number of protons and electrons in each
of the following common ions:
K+, Mg2+, Fe3+, Br–, Mn2+, C4–, Cu2+.
(Refer to the periodic table)

Ans: EXAMPLE-4

19 19 – 1 = 18 Write Nuclear symbol

12 12 – 2 = 10 For K+, given neutron
number for potassium

26 26 – 3 = 23 is 20

35 35 + 1 = 36 K39 +
25 25 – 2 = 23
19
6 6 + 4 = 10
29 29 – 2 = 27

Ans:EXERCISE – 6

“The chemical identity of an atom can be
determined solely from its atomic number (Z)”

It means if we want to identify what element
the atom is, we must refer to the
atomic number (Z) or number of protons.

Because the atomic number is unchanged
no matter the atoms are isotopes or become ions.

24 Mg
12

Ans: EXERCISE – 6

EXAMPLE:

12 24 – 12 = 12 12

12 25 – 12 = 13 12

12 26 – 12 = 14 12

12 24 – 12 = 12 10

MASS SPECTROMETRY

Technique used to determined relative
atomic mass and the relative abundance
of isotopes
Different atoms / isotopes / molecules can
be identified by their characteristic pattern of
lines (peak)

MASS SPECTROMETER

A device used to determined
Relative atomic mass and the
Relative Molecular mass
Relative Isotopic mass
Structural formula of compound

MASS SPECTROMETER 1.1-26

① vaporization chamber ④ magnetic field

⑤ ion detector

③ accelerating chamber
② ionization chamber

Mass Spectrum of Magnesium

⚫The line of mass

spectrum shows Mg

consists of three
63 isotopes:

8.1 9.1 24Mg, 25Mg and 26Mg.
⚫The height of each line

is proportional to the
24 25 26 m/e (amu) abundance of each

isotope.

⚫24Mg is the most

abundant of the three

isotopes

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Example: MASS SPECTRUM OF ISOTOPES

Intensity of peaks

1200Ne (90.2%)

22Ne (8.82%)

21Ne 10

10 (0.26%)

19 20 21 22

Atomic mass (amu)

Note: relative intensity = relative abundance

1.2 Mole Concept

Learning Outcome

At the end of this lecture, students should be able :
a) Define the term empirical and molecular formulae
b) Define term molarity, molality,mole fraction,
percentage by mass, percentage by volume.

matter 30

Definition of mole

Amount of substances that contains the

same number of particles (atoms, molecules,

formula units, ions) as there are atoms in

exactly in 12 g of C–12 Avogadro’s

1 mol contains 6.023 x 1023 particles number (NA)

EXAMPLE: 6.023 x 1023 C–12 atoms

1 mol of C–12 contains

1 mol of H2O contains 6.023 x 1023 H2O molecules
1 mol of NaCl contains 6.023 x 1023 NaCl formula units

EXAMPLE – 01

1 molecule of H2O :

1) ? hydrogen atom
1 molecule H2O consists 2 hydrogen atoms

2) ? oxygen atom
1 molecule H2O consists 1 oxygen atom

3) How many atoms in a H2O molecule?

Total atoms in 1 H2O molecule =
2 hydrogen atom + 1 oxygen atom

3 atomsMATTER= 32

In 1 mole of H2O :

1) How many water molecules?
1 mole water ~ 6.023 x 10 23 molecules

2) ? hydrogen atom

1 mole H2O molecule ~ 2 mole hydrogen atom

6.023 x 10 23 ~ 2 x 6.023 x 10 23

molecules hydrogen atoms

1 mol contains 6.02 x 1023 entities 33

MATTER

1 mole each of several elements:
copper, iron, carbon, sulfur and mercury

Each of them contain 6.023 x 1023 atoms

Molar Mass

⚫The mass of 1 mole of an element or 1 mole
of compound.

Unit : g mol-1

⚫Example: 24 g mol-1
- molar mass of Mg = (12 + 4) gmol-1
- molar mass of CH4 = 16 g mol-1
=

MATTER 35

MOLECULAR MASS

The sum of the atomic masses in a
molecule (unit : amu)

EXAMPLE:

1S 32.07 amu
2O + (2 x 16.00) amu
SO2 SO2 64.07 amu

MOLECULAR MASS Vs MOLAR MASS

For any compound
molecular mass (amu) =“nusmamereic”ally= molar mass (grams)

1 molecule / 1 mole (6.02 x 1023particles)
1 formula unit

H2O 18.02 amu 18.02 g
NaCl
58.44 amu 58.44 g

Micro World Macro World
atoms & molecules grams

EXAMPLE: H2O

Atomic Mass (1 atom)
Unit: amu

Ar or Mr Molecular Mass (1 molecule)
no unit Unit: amu 18 amu

18 Molar Mass (1 mol of
molecules)

Unit: g/mol 18 g/mol

For calculation of mole, use molar mass

CALCULATING MOLES

Number of mole
= Mass (g)

Molar Mass (g mol-1 )

Conversion factor:

EXAMPLE:

1 mol of Fe = 55.85 g of Fe
1 mol of Fe contains 6.023 x 1023 atoms Fe

MATTER 39

The mole concept provide the bridge
between mass and number of entities

GRAMS

use molar mass

MOLES

use Avogadro’s number

MOLECULES or ATOMS

1.2.1 Mole Concept of Gases

2 condition for molar volume of any gas,
⚫At s.t.p (standard temperature and pressure)
⚫At room temperature

MATTER 41

Calculate number of oxygen in in 56cm3 of C02

56 cm3 ≡ 0.056 dm3

a. 22.4 dm3 = 1 mole of CO2
0.056 dm3 = 0.0025 mole

b. Number of molecules CO2 = number of mol x NA
= 0.0025 x 6.023 x 1023

= 1.506 x 1021 molecules

a.1 molecule of CO2 = 2 O atoms

1.506 x 1021 molecule of CO2 = (1.506 x 1021 x 2 ) O atoms

= 3.011 x 1021 O atoms

MATTER 42

TYPES OF CHEMICAL FORMULA

Empirical Formula
Molecular Formula
Structural Formula
Formula Unit (for ionic compounds)

EXAMPLE: benzene 43

Empirical Formula = (CH)n
Molecular Formula = C6H6

Structural Formula =

MATTER

EMPIRICAL FORMULA:

Shows the simplest ratio of atoms of each
element in a compound.

MOLECULAR FORMULA:

Shows the actual number of atoms of each
element in a molecule of the compound.

EXAMPLE: Hydrogen peroxide 44

Empirical Formula = (HO)n
Molecular Formula = H2O2

MATTER

-The relationship between empirical formula and
molecular formula is :

Molecular formula = n (empirical formula)

Where ;

n = molecular mass @ molar mass
emprical formula mass

MATTER 45

MASS FROM CHEMICAL FORMULA

Ratio Composition by mass

CO2

What mass of C in CO2?
What mass of O in CO2?

Mass of element C =

Mass of CO2 molar mass of C (g/mol)
x

molar mass of compound (g/mol)

Concentrations of solutions in daily life

A SOLUTION

Homogenous mixture of two or more
substances

SOLUTE
Substance present in the smaller amount

SOLVENT

Substance present in the larger amount
use to dissolve solute
2 types of solvent,
i) non-polar (example; benzene)
ii) polar (common: water)

1.2-54

solvent water

CuSO4 solution
solution

solute
CuSO4

1.2.2 Concentration of Solution

Amount of solute present in a given quantity
of solvent or solution

Molarity (M)
Molality (m)
Mole fraction (X)
Percentage by mass (mass %)
Percentage by volume (volume%)

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