DK SMITHSONIAN SUPERSIMPLE CHEMISTRY

Elements

52 Elements

The Periodic Key Facts
Table
✓ The periodic table lists all known elements,
The periodic table lists all known 118
elements. Scientists organize elements in order of increasing atomic number.
in the periodic table according to their
atomic number and by the similar ✓ Horizontal rows are called periods.
properties they have as groups. ✓ Vertical columns are called groups.
✓ Trends (or patterns) relating to a property
Groups and Periods
can be seen as you go down or up a group.
Groups run from left to right.
1 2 Periodic table’s colors
Periods The colors used on this
Elements in the same period (row) have the 1 4 periodic table highlight
same number of electron shells (see page 28) elemental groups.
in their atoms (see page 26). For example, H Be
elements in period one have one electron shell,Periods run from top to bottom. 21 22 23 24
while those in period six have six electron shells. Hydrogen Beryllium
Groups Sc Ti V Cr
Members of a group (column) have the same 1 9
number of electrons in their outermost shells. Scandium Titanium Vanadium Chromium
For example, Group 1 elements have one 3 12
electron in their outer shell, while Group 7 45 47.9 50.9 52
elements have seven outer electrons. 1 Li Mg
Lithium 39 40 41 42
6.9 Magnesium
Y Zr Nb Mo
11 24.3
Yttrium Zirconium Niobium Molybdenum
2 Na 20
Sodium 89 91.2 92.9 95.9
23 Ca
57-71 72 73 74
19 Calcium
La-Lu Hf Ta W
3K 40.1
Potassium Hafnium Tantalum Tungsten
39.1 38
178.5 181 183.8
37 Sr
89-103 104 105 106
4 Rb Strontium
Rubidium Ac-Lr Rf Db Sg
85.5 87.6
Rutherfordium Dubnium Seaborgium
55 56
261 262 266
5 Cs Ba
Cesium
133 Barium

87 137.3

6 Fr 88
Francium
223 Ra

Radium

226

Lanthanides, a group of 57 58 59
elements, are listed here.
La Ce Pr
Actinides, a group of
elements, are listed here. Lanthanum Cerium Praseodymium

138.9 140.1 140.9

89 90 91

Ac Th Pa

Actinium Thorium Protactinium

227 232 231

Elements 53

Reading the Table 3 The atomic number
The element’s symbol
Each element has a unique one or two letter symbol. Li The element’s full name
These always start with a capital letter. These symbols The relative atomic mass
are used in formulas (see page 34) and equations Lithium
(see page 36), and are recognized in all languages.
The atomic number is the number of protons 6.9
in each of the element’s atoms. The relative atomic
mass is the average mass of an element’s atoms,
including all of its isotopes (see page 31).

Transition metals do not 3 4 5 6 7 0
have a group but they do
have similar properties, and 5 6 7 8 9 2
they can be found positioned
between groups 2 and 3. B C N O F He

Boron Carbon Nitrogen Oxygen Fluorine Helium

10.8 12 14 16 19 4

13 14 15 16 17 10

Al Si P S Cl Ne

Aluminum Silicon Phosphorus Sulfur Chlorine Neon

267 28.1 31 32.1 35.5 20.2

25 26 27 28 29 30 31 32 33 34 35 18

Mn Fe Co Ni Cu Zn Ga Ge As Se Br Ar

Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Argon

54.9 55.9 58.9 58.7 63.6 65.4 69.7 72.6 74.9 79 79.9 40

43 44 45 46 47 48 49 50 51 52 53 36

Tc Ru Rh Pd Ag Cd In Sn Sb Te I Kr

Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Krypton

96 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 83.8

75 76 77 78 79 80 81 82 83 84 85 54

Re Os Ir Pt Au Hg Tl Pb Bi Po At Xe

Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Xenon

186.2 190.2 192.2 195.1 197 200.6 204.4 207.2 209 209 210 131.3

107 108 109 110 111 112 113 114 115 116 117 86

Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Rn

Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Radon

264 277 268 281 272 285 284 289 288 293 294 222

118

Og

Oganesson

294

60 61 62 63 64 65 66 67 68 69 70 71

Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium

144.2 145 150.7 152 157.3 158.9 162.5 164.9 167.3 168.9 173 175

92 93 94 95 96 97 98 99 100 101 102 103

U Np Pu Am Cm Bk Cf Es Fm Md No Lr

Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium

238 237 244 243 247 247 251 252 257 258 259 262

54 Elements Key Facts

History of the ✓ In the 1800s, scientists were looking for patterns
Periodic Table
within the properties of the known elements.
At the end of the 19th century, scientists
studying the properties of elements found ✓ Mendeleev created the first periodic table, similar
patterns when they listed them in order of
increasing atomic mass. John Newlands to the one in use today, in 1869.
ordered elements by atomic mass, and
every eighth element has similar properties. ✓ Mendeleev left gaps in this table that predicted the
However, in 1869, Russian chemist Dmitri
Mendeleev improved his method. existence of elements that were discovered later.

Spaces were left for
elements that were
discovered later.

Some of the
elements were later

repositioned to sit
with others that had

similar properties.

Mendeleev’s
periodic table
Mendeleev created the first
periodic table. He left gaps
for elements that he knew
possibly existed because
of the properties of
neighboring elements.

Hydrogen Elements 55

Hydrogen is the first element in the periodic table, Key Facts
and the most common element in the Universe.
Hydrogen usually exists as a gas, and has the ✓ Hydrogen is a nonmetal.
smallest and simplest atoms of any element. ✓ Hydrogen is a gas at room temperature.
✓ Hydrogen is the lightest element in
Atomic structure
Hydrogen is usually diatomic (two atoms), the Universe.
each containing one proton and one electron.
They share their electrons and bond together ✓ Hydrogen is highly reactive and its
to form one hydrogen molecule.
combustion forms water.

✓ Hydrogen is usually diatomic.

Proton Electron
Proton

Electron

One hydrogen molecule

Lightest Element Hydrogen Water Molecules Oxygen atom
molecule
As a gas, hydrogen is When hydrogen burns, O
the lightest element Air molecules two hydrogen atoms (H)
because it has the form covalent bonds HH
smallest atoms, and so with one oxygen atom
also has the smallest (O) in the air. This Hydrogen atom
molecules. This is why reaction forms one
hydrogen-filled balloons molecule of water (H2O).
float upward in the air.
Hydrogen atom

56 Elements Key Facts

Metals ✓ Most elements are metals.
✓ Most metals are solids at
Over three-quarters of elements (see page 30) are
classified as metals. They share many properties room temperature.
that are very useful. Iron, aluminum, copper, and
zinc are the four most commonly used metals in ✓ Most metals are strong and shiny.
alloys (see page 89). The properties of nonmetals ✓ Metals are malleable and ductile.
are not as consistent as those of metals. ✓ Metals are good conductors

Most metals are of electricity.
shiny and able to
withstand ✓ Metals are good conductors
pressure.
of heat.

✓ Most metals have high melting

and boiling points.

✓ A few metals are magnetic.

Shiny and strong
Metals can resist forces without bending or
breaking. They are often shiny when their
surfaces have been polished.

Conduct electricity Delocalized electrons Electrons move in one
Metals can conduct move randomly. direction when
electricity because
electrons are able to move conducting electricity.
freely between their atoms.
Metals such as copper are
used in electrical wiring.

Conduct heat Heat applied to Heat causes electrons
Metals are good a metal rod. to vibrate. In metals,
conductors of heat the electrons move
because their atoms are freely and carry heat
tightly packed together. energy with them.
Heat energy causes atoms
inside metals to vibrate, Heat spreads through
causing them to bump into the metal rod.
each other, spreading heat
through the metal.

Elements 57

Malleable Ions are held together by
Metals are malleable—they can the opposite charge of their
be hammered into different delocalized electrons.
shapes. They are also ductile, and
can be stretched out into a wire. Ions can slide
over one another

while still being
held by electrons.

External force

Lump of gold Flattened gold

Magnetic Nonmetals
Magnets are objects that produce
a magnetic field, which attract Nonmetals generally have a range
the metals iron, cobalt, nickel, of properties, many of which are
manganese, and gadolinium. Only almost the opposite of metals.
these metals can be attracted by Nonmetals can be dull instead of
a magnet, or made into magnets. shiny, brittle, and easily broken
Most other metals are not magnetic. instead of malleable or ductile,
poor conductors of heat and
Iron filings are electricity, and have low melting
attracted to magnets. and boiling points. Not all
nonmetals have these properties
High melting points and there are a few exceptions.
Metals are made of positive Groups and their properties are
ions and negative electrons. covered in more detail in the
The attraction between the following pages.
two is very strong. Only very
high temperatures can
break this attraction, and
this is why many metals
have high melting points.

Molten metal is
usually viscous.

58 Elements Key Facts

Group 1 ✓ Group 1 metals are very reactive.
✓ Group 1 metals are shiny and soft.
Physical Properties ✓ Group 1 metals are good conductors

Group 1 elements (except hydrogen, see page of heat and electricity.
57) are also called the alkali metals. These
elements have such low melting points that ✓ Group 1 metals have very low melting and
they can be cut with a knife. They also have
such a low density that they float on water. boiling points.

✓ Group 1 metals are not dense.

Physical properties of Group 1
These metals are not found pure in nature. They must
be refined in a laboratory into their pure forms, and
held within glass cases so they don’t react with air.

Lithium Sodium Potassium Rubidium Cesium

Pure lithium Pure sodium Pure potassium Pure rubidium Pure cesium is
becomes dull when is a light is a light is a dark a silver-gold
exposed to air. silver color. silver color. color.
silver color.

Group 1 Elements 59

Chemical Properties Key Facts

Group 1 metals are dangerous because they ✓ Group 1 elements are very reactive.
react easily and violently in water and acid. They ✓ Group 1 elements have one electron in
also react with air to form compounds called
metal oxides. They react with water to form their outer shell.
alkaline compounds called metal hydroxides,
giving this group the name alkali metals. ✓ Group 1 elements react with nonmetals

Bright reaction to form ionic compounds.
Potassium reacts vigorously with
water to create potassium hydroxide Property Trends
(a type of metal hydroxide).
Group 1 elements become more reactive as you
Potassium Hydrogen gas go down the group. At the bottom of the group,
burns with a is released. electrons are far away from the nucleus. The
purple hue. electrostatic attraction (the attraction between the
negative electrons and positive nucleus) is weak.
Reactivity increasesThe weaker this attraction is, the easier it is for
electrons to be lost during a reaction—this is why
metals at the bottom of Group 1 are more reactive.

3

Li

Lithium

6.9

11

Na

Sodium

23

19

K

Potassium

39.1

37

Rb

Rubidium

85.5

55

Cs

Cesium

132.9

87

Fr

Francium

223

Francium’s electrons are further
away from its nucleus, so it is
more reactive than lithium.

60 Elements Key Facts

Group 2 ✓ Group 2 elements are metals.
✓ Group 2 elements are reactive.
Group 2 elements have metallic properties ✓ Group 2 elements have two electrons
(see pages 56–57). They are also called the
alkaline earth metals. They are reactive, but in their outer shells.
not as reactive as Group 1 elements.
✓ Group 2 elements typically react with
Physical properties of Group 2
Pure samples of Group 2 elements are shiny nonmetals to form ionic compounds.
and solids at room temperature.
Pure magnesium is
Pure beryllium silver-colored.
is dark gray.

Pure calcium
is silver to pale
yellow-colored.

Beryllium Calcium Magnesium

Pure strontium is Pure barium is
usually gray but silver-gray colored with
a yellow tint.
turns yellow when
exposed to air.

Strontium Barium

Radium and Decay Alpha Beta
particle particle
Radium, the last element
in Group 2 on the periodic Alpha decay Beta decay
table, has the largest atoms
of its group. Their nuclei may
undergo radioactive decay
(break up) and give out an
alpha particle (two protons
and two neutrons). They may
also lose an electron, giving
out a beta particle.

Group 3 Elements 61

Most of the elements in Group 3 are Key Facts
metals. They are less reactive than Group
1 and 2 elements. Most Group 3 metals ✓ Most of the Group 3 elements have
react with oxygen and water, forming
ionic metal oxides and hydroxides. metallic properties.

Physical properties of Group 3 ✓ Group 3 elements are less reactive
Most of the elements in Group 3 are shiny metals,
except boron, which is a dull nonmetal. than elements in Groups 1 and 2.

Pure boron is ✓ Group 3 elements have three
dark compared to
other elements in electrons in their outermost shells.
its group.
Pure aluminum is
silver-colored.

Gallium melts
slightly above room

temperature.

Boron Aluminum Gallium

Pure indium is Pure thallium is kept in
soft enough to glass vials to prevent it
carve lines into it.
reacting with air.

Indium Thallium

Artificial Element 113
113
Nihonium, at the bottom of Group 3, 183
is an artificial element that can be Nihonium atom
formed when scientists collide zinc
and bismuth atoms together. Nuclear
fusion (see page 253) occurs, and the
larger atom that forms is the element
nihonium. Moscovium (see page 68)
can also break down into nihonium.

62 Elements Key Facts

Transition ✓ Transition metals can be found in
Metals
the center of the periodic table.
The transition metals are a large group of elements
found in the center of the periodic table. They have ✓ They have a range of uses and properties
the typical properties of metals, and their atoms
can form many ions (see page 73). Many transition (most of them metallic).
metals are used as catalysts (see page 184) to
speed up production in the chemical industry. ✓ Most have more than one ion.
✓ Their ionic compounds are usually colorful.
Colorful solutions ✓ Some are good catalysts.
Transition metals form many colorful ionic
compounds that dissolve in water. They are
kept in tall flasks with markings that clearly
indicate the volume of each solution.

Chromium (C3+) is a
pale green color.

Titanium
solutions are

usually
colorless
unless with
certain anions.

Varying Colors V 2+ Elements 63

Transition metals can create V3+ has lost three electrons, so
different colored solutions, its solutions are lime green.
depending on how many electrons
their atoms have lost during a V3+ V4+
reaction. For example, vanadium
solutions may appear in three
different colors. Light interacts with
the varying amount of electrons in
different ways, producing different
colors in the solutions.

Tight stoppers are
fitted onto the flask
so air does not react
with the solution.

This nickel Copper ions
ion is a pale in a water
turquoise color.
solution are
usually a
pale sky

blue color.

64 Elements Key Facts

Lanthanides ✓ Lanthanides are elements with the atomic

Lanthanides are a group of elements with the numbers 57–71 on the periodic table.
atomic numbers 57–71 in the periodic table.
They have similar properties to transition metals. ✓ They are commonly found in Earth’s crust,
Lanthanides tarnish (lose their shine) easily in
air, and they are sometimes stored in argon or in compounds with other elements.
under oil to prevent this.
✓ Lanthanides are reactive and form ionic
Physical properties of lanthanides
Lanthanides are found mixed with other compounds with nonmetals.
elements in Earth’s crust, and must be
extracted and purified into pure samples. ✓ Lanthanides have large atoms.

Cerium Praseodymium

Lanthanum Pure europium has
golden crystals.

Pure samarium Europium
is silver-white.
Neodymium Samarium

Pure gadolinium
is hard.

Gadolinium Terbium Pure terbium is Thulium
so soft it can be
cut with a knife.

Common Uses Fluorescent bulb TV Guitar This metal
is made of
Lanthanides are used to samarium-
manufacture certain objects cobalt alloys.
because they have useful
properties. For example,
lanthanum used in bulbs
reduces the amount of yellow
light emitted, and some TV
screens have small amounts
of cerium, which emits color.

Actinides Elements 65

Actinides are the group of elements with the Key Facts
atomic numbers 89–103 in the periodic table.
They have similar properties to lanthanides, ✓ Many actinides are artificial.
but they are more reactive. Actinide atoms are ✓ Actinides are more reactive than
very large and are radioactive (see page 60).
Most of the elements in this group are artificial. lanthanides and react easily with air.

Physical properties of actinides ✓ Actinides have large atoms.
Pure samples of actinides are very ✓ Actinide atoms are radioactive.
rare because they are radioactive.
Actinides are usually found in trace
amounts inside certain minerals.

Autunite
(mineral containing
traces of actinium)

Monazite Torbernite
(mineral containing (mineral containing
traces of protactinium)
thorium)
Pure uranium is
Californium, an shiny and gray.
artificial actinide, are
contained in pellets in

the laboratory.

Californium Uranium

66 Elements Key Facts

Carbon ✓ Carbon is a nonmetal.
✓ Carbon is present inside all
Carbon is a nonmetal element that is
important because it can combine with living things.
many other elements to form millions of
natural and artificial compounds, including ✓ Carbon forms many different
carbon dioxide gas, plastics, and fuels.
compounds with other elements.
Carbon atom
One carbon atom Neutron
normally contains six
protons, six neutrons,
and six electrons.

Proton

Carbon-Based Life Tiger Electron

Carbon is one of four main Tree Fungi
elements (including hydrogen,
oxygen, and nitrogen) that make
up all living things. Carbon
atoms form complex molecules
essential for life, such as
DNA, proteins, carbohydrates
(see pages 224–26), and fats.

Group 4 Elements 67

Group 4 elements have quite different properties Key Facts
from each other. Carbon (see page 66) is
a solid nonmetal, silicon and germanium are ✓ Group 4 elements includes metals
semimetals, and the remaining three are metals.
and nonmetals.

✓ Group 4 elements have four electrons

in their outermost shell.

✓ Group 4 elements react with

hydrogen to form hydrides.

Physical properties of Group 4 Pure carbon can be Pure silicon Pure germanium
Group 4 elements in their pure very dark and shiny. is silver. is silver.
forms are all solids at room
temperature and shiny.

Carbon Silicon Germanium

Pure tin Pure lead is
is silver. dull and gray.

Tin Lead

Conductors of electricity Silicon atom

Pure silicon and germanium Free space for
are semiconductors. If a small electrons to
amount of another element, such move, so
as gallium (their atoms have electricity can
3 outer electrons), is added to be conducted.
either silicon or germanium, their
spare electrons allow electricity Gallium atom
to be conducted. Silicon wafer
chips used in computers are Silicon wafer
made of these alloys.

68 Elements Key Facts

Group 5 ✓ Group 5 elements vary in physical

Group 5 elements vary in their appearance and chemical properties.
and properties. They are also called the nitrogen
group, after the first element in the group. They ✓ Group 5 elements include both
range from nitrogen, a relatively unreactive
colorless gas, to bismuth, a shiny, solid metal. nonmetals and metals.

Physical properties of Group 5 ✓ Group 5 elements have five electrons
Aside from nitrogen, all of the
elements in Group 5 are solids in their outermost shells.
at room temperature.
Property Trends
Pure nitrogen is held in a
glass sphere and turns As we go down Group 5, the size of each
purple when electrified. element’s atoms increases. The elements
also become more metallic closer to the
Nitrogen Pure bottom of the group. Melting points, Density, melting points, and boiling points increase
phosphorus boiling points, and densities generally
can be a fine increase down the group.
red powder.
7
Pure arsenic Phosphorus
is black N
and shiny.
Nitrogen
Pure antimony
is silver, hard, 14

and brittle. 15

Arsenic P

Antimony Phosphorus

Pure bismuth reacts 31
with oxygen to form
colorful crystals. 33

As

Arsenic

75

51

Sb

Antimony

121.8

83

Bi

Bismuth

209

115

Mc

Moscovium

288

Moscovium, the last element in
Group 5, has the largest and
most dense atoms.

Bismuth

Group 6 Elements 69

Group 6 elements include the nonmetals oxygen and Key Facts
sulfur, the semimetals (properties of both metals and
nonmetals) selenium, tellurium, and the metal ✓ Group 6 contains semimetals and
polonium, and the artificial element livermorium. This
group is also called the oxygen group. Both nonmetals nonmetals.
react with metals to form ionic compounds.
✓ Group 6 elements are highly reactive.
✓ Group 6 elements contain six

electrons in their outermost shells.

Physical properties of Group 6 Pure sulfur is a fine
Most of the elements in Group 6 are solids at yellow powder.
room temperature, except oxygen, which is a
gas. Polonium and livermorium exist as tiny
trace amounts and are not pictured here.

Pure oxygen is
silver-blue when
electrified.

Sulfur

Oxygen Pure tellurium is
shiny and

silver-white.

Pure selenium is
shiny and gray.

Selenium Tellurium

70 Elements Key Facts

Group 7 ✓ Group 7 elements are nonmetals.
✓ Group 7 elements react with metals
Group 7 elements are highly reactive nonmetals. They
are also called the halogens (meaning “salt-forming,” to form ionic compounds.
because they react with metals to make salts, see
pages 141–42). These elements have many ✓ Group 7 elements are diatomic
properties, and some are used in common household
products, such as in disinfectants and bleaches. (consist of two atoms).

Physical properties of Group 7 ✓ Group 7 elements have seven
Most Group 7 elements are found
as gases. As you go down the group, electrons in their outermost shell.
they also get darker.
Pure bromine gas
Pure fluorine gas is red-brown.
is pale yellow.
Pure iodine crystals
are dark purple
and shiny.

Bromine

Fluorine Pure chlorine gas
is yellow-green.
Chlorine
Iodine
Property trends
Chlorine atoms are
Group 7 elements have seven electrons in able to take one more
their outer shell. Their outer shell can take electron in their
one more electron when it reacts with the outermost shell.
atoms of other elements. Group 7 elements
become less reactive as you go down the Chlorine atom
group. This is because their electrostatic
attraction (see page 59) becomes weaker.

Group 0 Elements 71

Group 0 elements are colorless, odorless gases Key Facts
with very low boiling points. They are also called
the noble gases or Group 8. The atoms of Group 0 ✓ Group 0 elements are colorless gases.
elements have full outer shells, so they can’t lose ✓ Group 0 elements have very low
or gain electrons and are therefore unreactive.
They are usually found as single atoms. boiling points.

Physical properties of Group 0 ✓ Group 0 elements all have full
Group 0 elements are gases at room
temperature. They are only visible when outer shells.
electrified within clear glass spheres.
✓ Group 0 elements are very unreactive.
Pure helium
glows purple Pure argon glows
when electrified. pale purple when

electrified.

Helium Neon Pure neon glows Argon
orange when
Pure krypton electrified.
glows blue-white
when electrified. Pure radon is a
transparent gas.

Krypton Xenon Pure xenon Radon
glows blue when
Unreactive elements electrified.

Most Group 0 elements are very Argon atoms’ outer shells
unreactive because their atoms cannot are full, and so cannot
take on any extra electrons. For example, take more electrons.
the outer shells in argon atoms have
eight electrons, and so are full.

Structure and
Bonding

Ions Structure and Bonding 73

Ions are atoms, or groups of atoms, that have gained or Key Facts
lost at least one electron. Electrons have a negative
charge, so if an atom gains electrons it becomes ✓ Ions are charged particles that
negatively charged (an anion). If an atom loses electrons,
it becomes positively charged (a cation). The charge form from a single atom or a group
corresponds to the number of electrons gained or lost. of atoms.

✓ Positive ions are called cations and

negative ions are called anions.

✓ The number of electrons gained or

lost equals the charge of the ion.

Loss One electron lost +
Some atoms lose electrons
to achieve a full outer shell. Ions are drawn inside a
square bracket with
A lithium atom loses the charge of the ion
its single outer written on the top right.

electron to form a
positive lithium ion.

Lithium atom Lithium ion Having lost its single outer
electron, the lithium ion’s
new outer shell is full.

Gain A fluorine atom needs to gain The electron gained
Some atoms gain an electron in its outer shell to completes the
electrons to achieve form a negative fluoride ion.
a full outer shell. -outermost shell.
One electron gained

Fluorine atom Fluoride ion

Transfer of Element Type Atom Ion Number of electrons
K K+ (potassium) gained or lost
Electrons Potassium Metal Ca Ca2+ (calcium) One lost
H
Metal atoms can only Calcium Metal O H− (hydride) Two lost
lose electrons to form O2− (oxide)
positive ions (cations). Hydrogen Nonmetal One gained
Nonmetal atoms can
either gain or lose Oxygen Nonmetal Two gained
electrons, but negatively
charged ions (anions)
are more common.

74 Structure and Bonding Key Facts

Ionic Bonding ✓ Ionic bonds form between metals

When metals and nonmetals react with each other they and nonmetals.
form ionic bonds—electrostatic attractions between
positive and negative charges. Metal atoms always lose ✓ During chemical reactions, atoms
negatively charged electrons to form positively charged
ions, while nonmetal atoms gain those same electrons to gain or lose electrons to achieve a
form negative ions. The resulting ions always have a full outer shell, which is more stable.
stable, full outer shell of electrons.
✓ Metals always lose electrons to form
Forming an ionic bond
Only atoms of the noble gases in Group 0 (see positive ions.
page 71) of the periodic table have full outer
shells of electrons. Other atoms achieve this ✓ When ionic bonds form, nonmetals
by gaining or losing electrons to form ions.
gain electrons to form negative ions.

Lithium loses its single Fluorine has seven The innermost shell of any The fluorine atom
outermost electron to electrons in its outer shell. atom can only hold two gains the electron
form a lithium ion. It needs to gain one to electrons. So lithium’s lost from lithium to
achieve a full shell of eight. form a fluoride ion.
outermost shell is now full.
-
Electron is +
transferred

Lithium atom Fluorine atom Lithium ion Fluoride ion

Why Ions Element Type Atom Electronic Ion Electronic
configuration formed configuration
Are Formed Na
Mg of atom of ion
Atoms lose or gain O
electrons to achieve a full Sodium Metal Cl 2, 8, 1 Na+ 2, 8
outer shell. As a result, the Magnesium Metal 2, 8, 2 Mg2+ 2, 8
electronic configuration of Nonmetal O2− 2, 8
the ion is always the same Oxygen Nonmetal 2, 6 Cl− 2, 8, 8
as the configuration of the Chlorine 2, 8, 7
nearest noble gas.

Structure and Bonding 75

Ions and the Key Facts

Periodic Table ✓ Metals in Groups 1, 2, and 3 lose electrons

Atoms have an equal number of protons and to form positive ions (cations).
electrons, which means they have no overall
charge. An ion is an atom (or group of atoms) that ✓ Nonmetals in Groups 5, 6, and 7 gain
has gained or lost at least one electron. Metals
tend to lose electrons, forming positively charged electrons to form negative ions (anions).
ions (cations). Nonmetals tend to gain electrons,
forming negatively charged ions (anions). ✓ Hydrogen is unusual because it can form

both positive and negative ions.

✓ Elements in the same group form ions with

the same charges.

Hydrogen can form both +1 and −1 ions. Group 7 elements form ions with a −1 charge. He

Group 1 elements form ions with a +1 charge. Group 6 elements
form ions with a −2 charge.
Group 2 elements form ions with a +2 charge.
Group 5 elements form
H ions with a −3 charge.

Li Be Group 3 elements form B C N O F Ne
Na Mg ions with a +3 charge. Al Si P S Cl Ar

K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr

Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te l Xe

Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Fr Ra Ac Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og

Predicting Charge Element Group Type Atom Ion Ions formed

The periodic table allows us Sodium 1 Metal Na Na+ Loses one electron
to predict the charge of an Magnesium 2 to form a sodium ion
ion by looking at its group 6 Metal
number. Elements in the Oxygen 7 Mg Mg2+ Loses two electrons to form a
same group (ignoring the Non- magnesium ion
transition elements) have the metal
same number of electrons in O O2− Gains two electrons to form
their outermost shell, which Non- an oxide ion
means they form ions with metal
the same charges.

Chlorine Cl Cl− Gains one electron to form
a chloride ion

76 Structure and Bonding Key Facts

Dot and Cross ✓ Dot and cross diagrams show the
Diagrams
arrangement of electrons in atoms,
Chemical reactions are all about moving electrons. ions, or simple molecules.
Dot and cross diagrams help us to visualize where
electrons start from and where they end up. Dot ✓ Each electron is represented by
and cross diagrams without circles around the
atoms are often called Lewis structures, after the a dot or a cross.
US scientist who first suggested the idea.
✓ For compounds, the diagram
Sodium fluoride
When sodium reacts with fluorine, an electron is transferred shows which atom the electrons
from the sodium atom to the fluorine atom, forming a originally came from.
positive sodium ion (Na+) and a negative fluoride ion (F−).
This makes the compound sodium fluoride (NaF).

The sodium electrons The fluorine electrons This electron in the -
are drawn as dots. are drawn as crosses. fluoride ion originally came

from the sodium atom.

+

Sodium atom Fluorine atom Sodium fluoride

Magnesium oxide Magnesium loses its
Magnesium forms 2+ ions, and oxygen forms 2− ions. This two outer electrons and
time, we only need one magnesium ion and one oxide ion to becomes an Mg2+ ion.
form neutral magnesium oxide (MgO).
2+ 2−

Magnesium atom Oxygen atom Magnesium oxide

Structure and Bonding 77

Sodium oxide The oxygen atom gains the 2−
Sodium forms 1+ ions while oxygen forms 2− ions. In two sodium electrons to
order to balance these charges and form a neutral form an oxide ion.
ionic substance, sodium oxide (Na2O), two sodium
atoms must combine with one oxygen atom. +

Each sodium atom gives up +
the single electron in its outer
shell, forming two Na+ ions. Sodium oxide

Oxide atom Each fluorine atom gains -
one magnesium electron -
Sodium atoms
to form a fluoride ion.
Magnesium fluoride
Magnesium fluoride (MgF2) is made up 2+
of Mg2+ ions and F− ions. Two F− ions are needed to
balance the 2+ charge on a single magnesium ion. Magnesium fluoride

The Magnesium atom
gives up two electrons
in its outer shell,
forming an Mg2+ ion.

Magnesium atom

Fluorine atoms

78 Structure and Bonding

Ionic Structures Key Facts

When metals and nonmetals react with each ✓ Ionic compounds are made up of
other, they form ionic compounds. Unlike simple
compounds such as water and carbon dioxide, alternating positive and negative ions.
these aren’t made up of individual molecules, but
instead are repeating, three-dimensional structures of ✓ The ions are held together by strong
positive and negative ions. This type of arrangement is
called a giant ionic lattice. electrostatic attractions between
positive and negative charges.

✓ This arrangement is called a giant

ionic lattice.

Sodium chloride Ball-and-Stick Models
While the “spacefill” diagram below shows just a few
ions, a single crystal of sodium chloride actually contains “Ball-and-stick” models are also used
around six hundred quadrillion sodium and chloride ions. to represent ionic structures, and can
make it easier to visualize how the ions
The repeating pattern of Each positively charged are arranged. However, the relative
sodium and chloride ions sodium ion is surrounded sizes of the ions may not be as clear,
by negatively charged and in reality the space between the
forms a giant ionic chloride ions. ions does not exist.
lattice structure.

Chloride Sodium
ion (Cl−) ion (Na+)

Each negatively Sodium chloride
charged chloride ion is
surrounded by positively The stick represents the strong
charged sodium ions. electrostatic attraction between
the positive and negative ion.
Sodium ions are smaller
than chloride ions.

Table salt, also known as sodium
chloride (NaCl), is made up of
sodium ions (Na+) and chloride
ions (Cl−) in a repeating pattern.

Structure and Bonding 79

Ionic Properties Key Facts

Ionic compounds have particular properties due ✓ There are strong electrostatic attractions
to their ionic lattice structure (see page 78). They
are crystalline when solid and generally have high between the ions in ionic compounds.
melting and boiling points, although there are
some exceptions. Ionic compounds can conduct ✓ Ionic solids tend to have high melting points
electricity when molten or dissolved in water, but
they do not conduct electricity when solid. because it takes a lot of energy to overcome

the attractions between ions.

✓ Solid ionic compounds do not conduct

electricity.

✓ When molten or dissolved in water, ionic

compounds do conduct electricity.

Crystals Sodium ions (Na+) +− +
Sodium ions and chloride ions + −+− +
are arranged in a regular, Chloride ions (Cl−)
repeating pattern in sodium
chloride crystals.

−+−+−

+− + −+

+−+ There are strong
electrostatic attractions
between the positive
and negative ions.

Sodium chloride is a The ions are not able to
solid at room move so they cannot
temperature. conduct electricity.

Melting and Dissolving The ions are able to
move so they can
In ionic solids, the ions cannot
move. When ionic compounds conduct electricity.
melt or dissolve, the ions break
down and are able to move and
carry an electrical charge. Some
ionic compounds dissolve easily
in water, but not all of them.

Solid Liquid

80 Structure and Bonding

Covalent Bonding Key Facts

A covalent bond forms when two atoms share a pair of ✓ Covalent bonds form when two
electrons between them. By sharing in this way, each atom
acquires a full outer shell of electrons, making it more stable. atoms share a pair of electrons.
Covalent bonds vary in strength, but generally require a lot
of energy to break, and so are considered strong. ✓ Atoms share electrons in order

Nonmetal atoms to acquire a full outer shell.
Covalent bonds can form between nonmetal atoms,
which may be the same, such as in the element ✓ Only electrons in the outermost
chlorine (Cl2), or different, such as in the compounds
water (H2O) or carbon dioxide (CO2). shell are shared.

The “stick” represents Two “sticks” represent two ✓ Covalent bonds form between
a shared pair of shared pairs of electrons,
nonmetal atoms.
electrons, called a called a double covalent bond.
single covalent bond. Carbon atom
Oxygen atom

Chlorine atom

Chlorine molecule (Cl2) Carbon dioxide
molecule (CO2)

Oxygen atom Hydrogen atom

Water molecule (H2O) Electrons are
represented by
How Covalent Each chlorine atom dots or crosses.
has seven electrons
Bonding Works By sharing a pair of electrons,
in its outer shell. a covalent bond forms and
The most stable electronic each atom effectively acquires
configuration (see page 29) for Covalent bonding a full outer shell of eight.
an atom is to have a full outer diagrams often only
shell of electrons. By sharing
electrons, each atom effectively show outer shell
gains one or more electrons to electrons as atoms
“fill” its outer shell and achieve only share electrons in
the same stable electronic
configuration as its nearest their outer shells.
noble gas (see page 71).

Representing Structure and Bonding 81

Covalent Bonds Key Facts

In molecules, covalent bonds form between atoms ✓ 3D structures show us the shape
when they share electrons with each other. A single
bond is formed when two atoms share one pair of of molecules.
electrons, a double bond is two shared pairs, and so
on. There are different ways to represent these ✓ Dot and cross diagrams show how
covalent bonds.
electrons are shared to form the
covalent bond or bonds.

✓ Structural formulas clearly show all

the atoms and bonds at a glance,
but only in two dimensions.

3D structures Nitrogen atom The two “sticks” represent a
Sometimes called “ball-and- double covalent bond between
stick” models, these show
atoms and the angles of bonds the oxygen atoms.
in a molecule. They are helpful
for visualizing shapes, but can
be confusing when we
consider larger molecules.

The “stick” represents a single Ammonia Oxygen atom Oxygen
covalent bond between a nitrogen molecule Hydrogen atom molecule

atom and a hydrogen atom.

Dot and cross diagrams A Lewis structure is a The oxygen atoms
These show how the electrons dot and cross diagram share two pairs of
are arranged and which atom without circles around electrons, forming a
the electrons came from. the atoms. double covalent bond.
Unlike other types of diagram,
they also show electrons that Ammonia The nitrogen electrons are Oxygen
are not involved in bonding, molecule represented by crosses and molecule
which can be useful for the hydrogen electrons by dots.
figuring out why molecules
have certain shapes.

Structural formulas Chemical symbols are Two lines represent a
These show how all the used to identify atoms. double bond between
atoms are connected in two
dimensions, and whether A single covalent the oxygen atoms.
bonds are double, single, or bond (one pair of
triple. They make it easy shared electrons) Oxygen molecule
to see how atoms are is shown as a single
connected at a glance. straight line between
two atoms.

Ammonia molecule

82 Structure and Bonding Key Facts

Simple Molecules ✓ A molecule is two or more atoms bonded together.
✓ Molecular bonds are covalent.
A molecule is made up of two or more atoms ✓ Molecules of the same substance always contain
joined by one or more covalent bonds. Simple
molecules, such as oxygen and water, are all the same number and type of atoms. For example,
around us. The atoms in a molecule may be of water molecules always contain two hydrogen
the same element or different elements. But atoms and one oxygen atom.
molecules of the same substance always contain
the same number and type of atoms. The atoms are joined by a
single covalent bond and each
Hydrogen Two hydrogen atoms
Hydrogen atoms each has a share in two electrons.
have one electron in
their outer shell and One hydrogen molecule
need a total of two
electrons to achieve The atoms are joined by double
a full outer shell. covalent bonds and each has a
share in eight electrons overall.
Carbon dioxide
Carbon dioxide is a
simple molecule with
the formula CO2.
Carbon and oxygen
are bigger atoms
than hydrogen—
they need eight
electrons to achieve
a full outer shell.

One carbon and two oxygen atoms One carbon dioxide molecule

Water The atoms are joined by
Water (H2O) contains single covalent bonds.
hydrogen and oxygen.
Each hydrogen atom only One water molecule
needs two electrons to
have a full outer shell,
while an oxygen atom
needs eight in total.

One oxygen and two hydrogen atoms

Properties of Structure and Bonding 83

Simple Molecules Key Facts

The atoms in molecules such as water ✓ The atoms in simple molecular substances
(H2O) and chlorine (Cl2) are held together by
covalent bonds. Between individual molecules, are held together by covalent bonds.
there are weak forces of attraction called
intermolecular forces. It takes relatively little ✓ Intermolecular forces of attraction
energy to disrupt these forces, so simple
molecules tend to have low melting and between individual molecules are weak.
boiling points.
✓ Most simple molecular substances are
Chlorine
Chlorine (Cl2) is a simple gases or liquids at room temperature
molecular substance with and pressure.
weak intermolecular
forces between individual ✓ Simple molecular substances are also
Cl2 molecules. It’s a gas
at room temperature called simple covalent substances.
and pressure with a
boiling point of Chlorine atoms in
−29.2°F (−34°C). molecules are held
together by a shared
pair of electrons (or a

covalent bond).

Chlorine is a yellow–green There are weak forces
gas at room temperature of attraction, known as
and pressure. intermolecular forces, between
individual chlorine molecules.
Intermolecular Forces
Strong Intermolecular forces in
When simple molecular covalent bond water are stronger than
substances melt or boil, only the those between smaller
intermolecular forces between
molecules are broken, not the oxygen molecules.
covalent bonds. Larger molecules
have stronger intermolecular Strong
forces, and higher melting and covalent bond
boiling points, but the types of
atoms make a difference as well. Weak intermolecular
forces
Oxygen Water

84 Structure and Bonding Key Facts

Polymers ✓ Polymers are formed from many

Polymers are very big molecules—sometimes called smaller molecules called monomers.
macromolecules—that form when lots of monomers
(smaller molecules) join together in long chains. ✓ Monomers join together to produce
Polymers have useful properties, and in particular
they can be very strong. They occur naturally and long polymer chains of repeating units.
can also be made artificially. For more on polymers,
see pages 213, 214, 222, 260 and 261. ✓ The monomers can be different or can

The outer layer of be all the same type of molecule.
this hair shaft has
overlapping scales ✓ Most polymers are held together with
of keratin.
covalent bonds.

Human hair
There are many different polymers in our
bodies. This is a strand of human hair that
has been magnified under a microscope.
Hair is made of keratin—a natural polymer
that’s also found in our nails.

The atoms in the keratin
polymer are joined by
covalent bonds.

How Polymers Form Monomer ++ Smaller molecules
(monomers) join end
Both natural and artificial polymers, Polymerization to end to form long
such as plastics, are made from polymer chains.
lots of smaller molecules called
monomers. Some polymers are
made from one type of monomer,
but proteins (see page 225) such
as keratin form from different types
of monomers (amino acids).

Polymer

Covalent Network Structure and Bonding 85
Solids
Key Facts
Covalent network solids are made up of many
atoms arranged in a repeating pattern, called a ✓ Covalent network solids are made up
lattice. All the atoms are connected by covalent
bonds to form very strong substances. For more of many atoms joined by covalent bonds
on the properties of covalent network solids, and arranged in a repeating, 3D pattern
see page 86. called a lattice.

Silicon dioxide ✓ They have high melting points and tend
The silicon and oxygen
atoms in silicon dioxide, to be hard.
also known as silica, are
joined by covalent bonds ✓ Most covalent network solids have no
and arranged in a giant
repeating lattice. charged particles that are free to move,
so do not conduct electricity.

Covalent bonds
link all of the
atoms together.

Each silicon atom
bonds covalently to
four oxygen atoms.

Oxygen–silicon
bonds are very
strong and cannot
be easily broken.

Silicon atom
Oxygen atom

Silicon dioxide (SiO2)

Silicon Dioxide The mineral form of
silicon dioxide is
It takes a lot of energy to break the bonds in
covalent network solids, so silicon dioxide called quartz. Quartz
has a very high melting point. Silicon dioxide is the main mineral
does not easily conduct electricity as it does component in sand.
not have any delocalized electrons that are
free to move around.

86 Structure and Bonding Key Facts

Allotropes of Carbon ✓ Allotropes are forms of an

Allotropes are forms of an element that are in the element in the same physical state
same physical state but with different arrangements but with different arrangements
of atoms. Diamond, graphite, and graphene are three of atoms.
allotropes of carbon. They are all solids at room
temperature and are covalent network solids (see ✓ Diamond, graphite, and graphene
page 85), but have different properties because of
the differences in their structures. are three allotropes of carbon.

Diamond Diamond is the ✓ Diamond, graphite, and graphene
Each carbon atom in diamond is hardest naturally
covalently bonded to four others. occurring substance. have different properties because
Diamond is very hard and it does of differences in their structures.
not conduct electricity, although
it is a good conductor of heat. It takes a lot of
energy to break all
the covalent bonds
in diamond, so it
has a very high
melting point.

Graphite The carbon atoms
Each carbon atom in graphite is in graphite form
covalently bonded to three others,
leaving one free electron. These free layers of hexagons.
electrons become delocalized, giving
graphite particular properties, Layers can slide
including high electrical conductivity. over each other
as the attraction
The covalent bonds cannot be between them
broken easily, so graphite has is weak.

a high melting point. The carbon atoms
in graphene are
Graphene Graphene is almost arranged in hexagons.
Graphene is essentially a transparent and very light.
single layer of graphite. It
is extremely strong, very
lightweight, and can be used to
enhance the strength of other
materials. It is better at
conducting electricity
than many other materials.

Fullerenes Structure and Bonding 87

Fullerenes are another allotrope of carbon (see Key Facts
page 86). They are large molecules of pure carbon,
shaped like balls or tubes. The first fullerene to be ✓ Fullerenes are large carbon molecules
discovered, buckminsterfullerene (C60), was
discovered in 1985 and was named after the shaped like balls or tubes.
American architect R. Buckminster Fuller, who
was famous for building dome structures. ✓ One of the best-known fullerenes is

Buckminsterfullerene buckminsterfullerene (C60) in which the
Buckminsterfullerene is the atoms are arranged in hexagons and
most common naturally pentagons to form a ball.
occurring fullerene and
small amounts of it are ✓ Fullerenes can be made to form around
found in soot. Its molecules
are also known as another atom or molecule, which is then
“buckyballs” because trapped inside.
of their spherical shape.
Each carbon atom is
bonded to three others.

The carbon atoms Buckminsterfullerene
are connected by is a hollow sphere.

covalent bonds. Carbon nanotubes
are like a sheet of
60 carbon atoms are graphene (see
arranged in 12 page 86) rolled
into a tube.
pentagons and 20 Nanotubes are just
hexagons, like a ball. a few billionths of a
meter across, but
Nanotubes they can be many
centimeters long.
Nanotube structures have a diameter of
just a few billionths of a meter, but are
thought to be the strongest and stiffest
materials yet discovered. They are used in
electronics, solar cells, and in composite
materials, such as sport equipment,
because of their lightness and strength.

88 Structure and Bonding Key Facts

Metallic Bonding ✓ Metals have giant structures, with

In a piece of metal, the outer shell electrons of all particles arranged in a lattice pattern.
the ions are delocalized around positive metal ions
in a fixed lattice. The free electrons allow metals to ✓ The outer shell electrons are
conduct electricity. The electrostatic attractions
between all the electrons and the metal ions result delocalized (free to move around).
in most metals having high melting points.
✓ This results in positive metal ions
How metallic bonding works
In metals, the electrons are free to move around the surrounded by a “sea” of negatively
positive metal ions. This means metals have “mobile charged electrons.
charge carriers”—the electrons—so they all
conduct electricity, although some are better ✓ As the electrons are free to move,
conductors than others.
metals are good electrical conductors.
The ions are arranged
in layers to form a The delocalized electrons are free to move
around the lattice structure, which allows
giant lattice structure. metals to conduct electricity.

The particles of gold are held
together by forces of
electrostatic attraction
between the metal ions and
the delocalized electrons. This
is called metallic bonding.

Positive metal ions

Gold Gold is a solid at
room temperature—its
Gold has a high melting point because structure consists of closely
a lot of energy is needed to overcome
all the electrostatic attractions between packed metal ions.
the ions and the negatively charged
electrons within its structure.

Structure and Bonding 89

Pure Metals Key Facts
and Alloys
✓ Most alloys are combinations of two
An alloy is a combination of two or more metals, or a
combination of metals with nonmetallic elements. or more metal elements, but some
Alloys have different properties from the elements used to contain nonmetals such as carbon
make them and, in particular, are sometimes harder than or sulfur.
any of the pure metals used to make them. Some everyday
alloys include steel, bronze, brass, and amalgam (used in ✓ Alloys are always harder than the
dentistry)—for more examples, see page 262.
pure metals used to make them,
Iron alloy because differently sized atoms make
Iron (Fe) is a silvery-gray metal that reacts readily it more difficult for the layers
with oxygen and water to form rust (see page 264). to slide over each other.
Steel is an alloy of iron with a very small amount of
carbon, and is harder and stronger than pure iron. The alloy steel is much harder
than pure iron and is often
Pure metals are often used in construction.
softer than alloys.

Iron The atoms can be forced to Steel
slide over each other, by
Alloy Hardness Adding atoms of another
actions such as hammering. element makes it more
Alloys are made by combining difficult for the layers to
two or more pure elements. Pure metal slide over each other.
Atoms of different elements
have different sizes, making it Alloy
more difficult for the layers to
move over each other, and as
a result alloys are harder than
pure metals.

States
of Matter

Solids States of Matter 91

Solids are one of the three key states of matter. Key Facts
Unlike liquids and gases, solids keep their shape and
do not flow to the sides of a container. The particles ✓ The particles in solids are held in
in a solid can’t easily move past one another, but at
any temperature above −459.4°F (−273°C)— fixed positions by forces of attraction.
absolute zero—they do constantly vibrate in place.
✓ The particles vibrate in their fixed
Ice cube
Ice is the solid form of water positions.
(H2O). The water molecules
are in fixed positions and ✓ Because particles cannot move from
cannot move over each
other, unless the ice their positions, solids have a fixed
melts and becomes shape and do not flow.
liquid water.
The particles are arranged
in a repeating pattern.

Ice is rigid and
does not flow until

the temperature
increases and it
begins to melt.

The particles in a solid
are packed closely
together and do not have
space to move around.

Properties of Solids

Having particles in fixed positions Volume and shape Density and compressibility Flow
gives solids a set of properties that
distinguish them from liquids and Solids have fixed shapes Since the particles are close Forces of attraction stop
gases. They have a fixed shape, tend with defined edges. Their together, most solids have particles in a solid moving
to be dense, and do not flow to fill a volume changes only a high density, and can’t over each other; solids do
container they’re placed in. They slightly with temperature. easily be compressed. not flow.
also cannot be compressed.

92 States of Matter Key Facts

Liquids ✓ Particles in a liquid are arranged

When a substance is in its liquid form, its randomly and are free to move
particles have gained enough energy to move over and past each other.
past each other. As a result, liquids flow to the
edges of their container and form a nearly flat ✓ Liquids flow to the edges of a
surface. However, although the shape of a
liquid changes to fit the shape of its container, container and form a flat surface.
the total volume remains the same.
✓ The volume of liquids changes only
Water
The word “water” is usually used slightly with temperature.
to describe the liquid state of
the compound H2O. ✓ The particles are very close together,

Water is a colorless so liquids are not easily compressed.
liquid at room
temperature.

The particles are
packed tightly but are
randomly arranged
and can move over
each other.

Properties of Liquids

When a substance is in the Volume and shape Density and compressibility Flow
liquid state, it means its
particles have gained enough Liquids flow to the edges of Liquids have a high The particles in a liquid are
energy (usually in the form of a container, but while their density, so can’t be easily free to move over each other,
heat) to overcome some of the shape may change, the total compressed as their particles so liquids flow and can pass
forces of attraction holding volume stays the same. are close together. through narrow spaces.
them together in a solid. The
particles can now move over
each other, giving liquids
particular properties.

Gases States of Matter 93

Substances exist as gases when their Key Facts
particles gain enough energy to overcome
the forces of attraction keeping them ✓ Particles in a gas are very far apart.
together. Gases are less dense than solids and ✓ Gases have a low density—there are
liquids, and so are easy to compress. Gases have
no fixed shape, and their volume is very sensitive few particles in a large volume.
to temperature and pressure.
✓ The particles are constantly moving

—they move in straight lines until they
collide with another particle.

✓ Gases do not have a fixed shape.

Iodine forms a purple
gas when it’s heated.

Gases spread
quickly in all

directions.

Iodine The particles in a
Iodine sublimes (changes gas are typically
straight from a solid to a far apart.
gas) when heated. This is
because the attractions The particles have
between particles are space to move
quite weak, and it doesn’t randomly.
take much energy
to overcome them.

Properties of Gases Volume and shape Density and compressibility Flow
Gases have no fixed volume Gases have a low density and Gas particles are completely
When a substance is in its and take the shape of the can be easily compressed as free to move and can pass
gaseous state, it means its container they are in. their particles are far apart. through very small gaps.
particles have gained enough
energy to overcome the forces
of attraction between them. The
particles move freely, giving
gases particular properties.

94 States of Matter

Diffusion Key Facts

in Liquids ✓ Particles in liquids move randomly.
✓ Diffusion is the process where the particles
The particles in a liquid, such as water, are
constantly moving. If another substance is added, of one substance mix with another.
its particles bump into the water particles, causing
the new particles to move around and mix with the ✓ The random movement of particles allows
water. This process is called diffusion and it happens
spontaneously, without any need for stirring. the two substances to eventually mix
evenly without shaking or stirring.

✓ Particles in liquids keep moving, even

after they have completely mixed.

Dissolving purple dye in water The color spreads Eventually, the
When brightly colored dye is added to through the liquid water and the dye
water, the particles diffuse and the mixture
gradually becomes an even purple. by diffusion. are thoroughly
mixed together.
At first, the colored dye is
concentrated in one place.

How Diffusion
in Liquids Works

When the particles of a substance
are placed in water, they gradually
move from areas of high
concentration to low concentration
to become evenly spread.

The water and
dye molecules
move around
each other as
they start to mix.

Before diffusion

The particles
of dye diffuse
among particles
of water, and
eventually both
substances are
evenly mixed.

After diffusion

States of Matter 95

Diffusion in Gases Key Facts

In gases, particles move very quickly in all directions. ✓ Gas particles move very fast,
When two gases are allowed to mix, the particles of both
substances spread out in all directions, moving from an bumping into each other.
area of high concentration to one of low concentration.
This diffusion of gases happens spontaneously, as does ✓ When two different gases meet,
diffusion in liquids (see page 94) and solids.
their particles spread out, mixing
Bromine with each other.
Bromine (Br2) forms an orange–brown gas
under atmospheric pressure. Here, we see ✓ As they spread out, they end up
bromine gas diffusing into a container of air.
moving from areas of high
How Diffusion concentration to areas of low
in Gases Works concentration.

When the barrier is
removed, bromine gas
diffuses into the jar
containing air.

Gas particles move randomly.
When mixed, they gradually move
from areas of high concentration
to areas of low concentration to
become evenly spread.

Air particles are A barrier
spread out. between the
two jars stops
At the start, the the gases
bromine particles from mixing.
are closer together.

Before diffusion

Bromine particles Bromine Air moves into
become evenly mixed gas the jar that
with the air particles.
originally held
just bromine.

Eventually,
both jars are
evenly mixed.

After diffusion

96 States of Matter

Changes of State Key Facts

Changes of state—between solid, liquid, and gas—are ✓ Changes of state occur when
physical changes, meaning no chemical changes are taking
place. These changes are related to temperature (and a pure substance is heated or
pressure) and are reversible. A pure substance, containing cooled, or experiences a
only one element or compound, is a solid below its melting change in pressure.
point, a liquid at temperatures between its melting and
boiling point, and a gas above its boiling point. ✓ A pure substance is a solid

States of matter Liquids form when below its melting point, a
Water exists in three states— gases condense. liquid between its melting and
ice (solid), water (liquid), and boiling point, and a gas above
steam (gas). Ice melts to form its boiling point.
liquid water, and water boils
to form steam. Under certain ✓ As substances warm up, their
conditions, it can also
sublime (go straight particles gain energy to move.
from solid to gas).
Gas is formed when a liquid
reaches its boiling point.
Melting Boiling
Freezing Liquid Condensing

Solids form when Blue arrows
liquids freeze. represent cooling.

Sublimation

Solid Deposition Gas

How Particles are Arranged Red arrows In a liquid, particles are still touching,
represent warming. but now they’ve acquired enough
A simple model can be used to energy to move over each other.
represent how the particles in solids,
liquids, and gases are arranged. These In a gas, there are
diagrams have limitations—for example, very large gaps
drawn to scale, gas particles would be between particles,
much further apart than shown here. so the particles
are completely
In a solid, the particles free to move.
are tightly packed and
cannot move past each other,
but they do vibrate in position.

Heating and States of Matter 97

Cooling Curves Key Facts

Heating and cooling curves give information about ✓ Heating and cooling curves show
energy changes that happen when a substance
changes state. A substance is heated or cooled and what happens to the temperature of a
time and temperature are recorded to obtain substance when it is heated or cooled
information for the graph. The curves show us that over a period of time.
temperature does not change significantly during
changes of state, indicating that energy is absorbed ✓ A substance absorbs heat energy
(or released) by the substance.
from its surroundings when it melts
or boils, and energy is transferred to
the surroundings when it freezes
or condenses.

✓ The temperature of a substance remains

the same during changes of state.

Heating curve Temperature
A heating curve
experiment is carried out Boiling Gas Energy is taken in to
by gradually warming a Liquid break bonds.
substance and measuring Boiling
the temperature change point Melting The horizontal
over time. These graphs sections represent
have a characteristic Melting melting and boiling.
“stepped” shape. point

The temperature Solid
increases over time as the
Time
substance is warmed.

Cooling curve Temperature
A cooling curve
experiment is carried out Gas Energy is given out
by cooling a substance as bonds form.
and measuring the Condensation Condensing Liquid
temperature change point The temperature
over time. Its shape is Freezing Solid decreases over
similar to a heating Freezing time as the substance
curve, but reversed. point is cooled.

The horizontal Time
sections represent
condensing and freezing.

98 States of Matter Key Facts

State Symbols and ✓ State symbols show the physical
Predicting States
state of each substance in a
State symbols are added to equations to provide chemical reaction.
extra information about what’s happening. There are
four—(s), (l), (g), and (aq), representing solid, liquid, ✓ (s), (l), (g), and (aq) represent solid,
gas, and aqueous (dissolved in water) respectively.
We can figure out the state of a substance at a given liquid, gas, and aqueous (dissolved in
temperature if we know its melting and boiling points. water) respectively.

✓ The state of a substance at a given

temperature can be predicted if its
melting and boiling points are known.

States and equations Solid sodium reacting The solution turns pink because phenolphthalein
Here, sodium and with liquid water. indicator (see page 134) has been added and
water react to form aqueous sodium hydroxide is an alkali.
hydrogen gas and an
aqueous solution of Bubbles of Aqueous sodium
sodium hydroxide. The hydrogen gas form. hydroxide also forms.
physical state of each
substance is shown in
the balanced chemical
equation below.

sodium + water hydrogen + sodium hydroxide

2Na(s) + 2H2O(l) H2(g) + 2NaOH(aq)

Predicting States Element Melting point Boiling point
Oxygen –362.2°F (–219°C) –297.4°F (–183°C)
Below melting point, Gallium 4,044°F (2,229°C)
substances are solids. Bromine 86°F (30°C) 138.02°F (58.9°C)
Between melting and boiling 19.4°F (–7°C)
points, substances are
liquids. Above melting point,
substances are gases.

Question Figuring it out Answer

Which of the substances in 1. Oxygen boils at −297.4°C (−183°C), so Bromine is the only
the table would be a liquid substance that
at room temperature? is a gas at all temperatures above that. would be a liquid at
Assume room temperature room temperature.
is 68°F (20°C). 2. Gallium does not melt (become liquid) until

86°F (30°C), so will be solid at 68°F (20°C).

3. Bromine melts at 19.4°F (−7°C) and does

not boil until 138.02°F (58.9°C).

Nanoscience
and Smart
Materials

100 Nanoscience and Smart Materials Key Facts

Nanoparticles ✓ The size of a nanoparticle is between

Nanoparticles are tiny particles made up of a few 1 nm and 100 nm.
hundred atoms. A nanometer (nm) is one billionth
of a meter (1x10−9 m) in length, and nanoparticles ✓ One nanometer is equal to one
are between 1 nm and 100 nm in diameter.
Nanoparticles cannot be seen with the naked eye, billionth of a meter.
or even an optical microscope—an electron
microscope is needed to observe them. ✓ Nanoparticles can be only seen

Tiny particles under electron microscopes.
Nanoparticles are found in
nature, but can also be A nanoparticle is
made in the laboratory. usually made up of a
These images show few hundred atoms.
computer-generated
illustrations of
nanoparticle spheres.

A nanoparticle can
be between 1 and
100 nm wide.

How Big Are Nanoparticles? Particle Diameter
Atom 0.1 nm
Nanoparticles are between 1 and 100 nm in diameter. 0.5 nm
The table shows the size of nanoparticles compared to Small molecule 1–100 nm
other objects. More than 1,000 nanoparticles would fit Nanoparticle 7,000 nm
across the width of a single human hair, and about Red blood cell 100,000 nm
1 million nanoparticles would fit across the head of a pin. Human hair