Chemical Bonding

1. 11
LEARNING OUTCOMES
 Explain the formation of ionic bonds;
 Define and give examples of ionic solids;
 Explain the formation of covalent bonds;
 Define and give examples of simple
molecular solids;
 Explain metallic bonding;
 Relate the structure of sodium chloride to its
properties;
Chemical Bonding
Chapter 7

2. 22
LEARNING OUTCOMES
 Distinguish between ionic and simple
molecular solids;
 Explain the term allotropy;
 Define and give examples of giant molecular
solids;
 Relate the structure of diamond and graphite
to their properties
Chemical Bonding
Chapter 7

3. 33
The Electronic Structure
of Noble Gases
 The noble gases like helium, neon and argon, which are in
Group 0 of the Periodic Table, are very unreactive.
 They do not form bonds with other atoms.
 They have fully filled outermost (valence) shells.
 Except for helium, which has 2 outer electrons, all the other
noble gases have 8 outer electrons.
Chemical Bonding
Chapter 7

4. 44
The Electronic Structure
of Noble Gases
 The outer shell of 8 electrons is called an octet
structure and it makes the atom very stable.
E.g. Helium, neon, argon
 Atoms of other elements become stable like the
noble gases by losing or gaining electrons or by
sharing electrons.
 They achieve this by forming bonds with other
atoms.
Chemical Bonding
Chapter 7

5. 55
Types of Bonds
Covalent Bond Ionic Bond
Sharing of Electrons Transfer of Electrons
Between Non-metals Between Metal + Non-metal
Chemical Bonding
Chapter 7

6. 66
Ionic Bonds
 When sodium reacts with chlorine, the sodium atom loses
an electron to become a positively charged sodium ion:
Chemical Bonding
Chapter 7

7. 77
Ionic Bonds
 The chlorine atom gains an electron to become a
negatively charged chloride ion:
Chemical Bonding
Chapter 7

8. 88
Ionic Bonds
 The positive sodium ion and the negative chloride ion then
attract each other to form sodium chloride.
 Sodium chloride is called an ionic compound.
Chemical Bonding
Chapter 7

9. 99
Other ionic compounds
 Another example of an ionic
compound is that formed
between magnesium and
chlorine.
 Each magnesium atom
transfers 2 electrons, one to
each chlorine atom, to form
magnesium chloride.
The formula of magnesium chloride is therefore
given as MgCl2.
Chemical Bonding
Chapter 7

10. 1010
Quick check 1
1. Ionic bonds are formed between a ______ and a _____.
2. A metal atom ______ an electron to form a _______ ion while
a non-metal ______ an electron to become a ________ ion.
3. The two oppositely charged ions ________ each other to form
an ______ compound.
4. An ionic bond is formed by the _________ of _______.
5. (a) Is aluminium oxide an ionic or covalent compound?
(b) State the formula of aluminium oxide.
Solution
Chemical Bonding
Chapter 7

11. 1111
1. Ionic bonds are formed between a metal and a non-metal.
2. A metal atom loses an electron to form a positive ion while
a non-metal gains an electron to become a negative ion.
3. The two oppositely charged ions attract each other to form
an ionic compound.
4. Ionic bond is formed by the transfer of electrons.
5. (a) Aluminium oxide is an ionic compound.
(b) Al2O3
Return
Chemical Bonding
Chapter 7
Solution to Quick check 1

12. 1212
Covalent Bonds
 To achieve a more stable structure like helium, it needs one
more electron in the first shell.
 So two hydrogen atoms join together and share their
electrons. A hydrogen molecule is formed.
 A hydrogen atom has only one electron in its first shell.
Chemical Bonding
Chapter 7

13. 1313
Covalent Bonds
 This sharing of electrons is called covalent bonding.
 In an oxygen atom, the outer shell has 6 electrons, so to achieve
an octet structure of 8 electrons like neon, two oxygen atoms
combine to share 4 electrons.
This is called a double bond.
Chemical Bonding
Chapter 7

14. 1414
Other covalent molecules
Water
H2O (2 single bonds)
Methane
CH4 (4 single bonds)
Chemical Bonding
Chapter 7
OOHH HHCC
HH
HHHH
HH

15. 1515
Quick Check 2
1. The joining of atoms to form a molecule is called
__________ ________ .
2. The two types of bonds are ________ bond and
________ bond.
3. Covalent bonds are formed by the _________ of
_________ .
4. Ionic bonds are formed by the __________ of_________ .
5. _________ ______ are formed between non-metals
e.g. hydrogen, oxygen and carbon.
Solution
Chemical Bonding
Chapter 7

16. 1616
1. The joining of atoms to form a molecule is called
chemical bonding .
2. The two types of bonds are covalent bond and
ionic bond.
3. Covalent bonds are formed by the sharing of
electrons .
4. Ionic bonds are formed by the transfer of
electrons .
5. Covalent bonds are formed between non- metals e.g. hydrogen,
oxygen and carbon.
Return
Chemical Bonding
Chapter 7
Solution to Quick check 2
Lesson 2

17. 1717
Properties of Covalent Compounds
 The intermolecular forces
between the molecules are
weak so covalent
compounds have low melting
and boiling points.
For example, water, a
covalent compound, has a
melting point of 0 o
C and a
boiling point of 100 o
C.
Weak intermolecular
forces
Chemical Bonding
Chapter 7

18. 1818
Properties of Covalent Compounds
 Covalent compounds do not
conduct electricity in any
state.
 Most covalent compounds
are insoluble in water.
Instead they are soluble in
organic solvents.
For e.g. iodine is insoluble in
water, but soluble in ethanol. Pure water does not
conduct electricity
waterwater
Chemical Bonding
Chapter 7

19. 1919
Properties of Ionic Compounds
 The electrostatic forces
between the oppositely-
charged ions are very strong
so ionic compounds have
very high melting points and
boiling points.
For e.g. sodium chloride, an
ionic compound, has a
melting point of 801 o
C and a
boiling point of 1 517o
C.
Chemical Bonding
Chapter 7

20. 2020
Properties of Ionic Compounds
 Ionic compounds conduct
electricity when molten or
dissolved in water. This is
because the ions can move about
and conduct electricity.
Molten sodium
chloride conducts
electricity.
 Most ionic compounds are soluble in
water, but insoluble in organic solvents.
For e.g. sodium chloride is soluble in
water, but insoluble in oil or petrol.
Chemical Bonding
Chapter 7

21. 2121
Summary
Ionic Compounds Covalent Compounds
Have very high melting and boiling
points
Have low melting and boiling points
Conduct electricity when molten or in
aqueous solution
Cannot conduct electricity in any state
Are usually soluble in water, but
insoluble in organic solvents
Are usually insoluble in water, but
soluble in organic solvents
Differences between Ionic and Covalent Compounds
Chemical Bonding
Chapter 7

22. 2222
Quick check 3
1. Covalent compounds have _______ forces of attraction
between the molecules, so they have ____ melting points and
______ boiling points.
2. Ionic compounds have very ______ forces of attraction
between the oppositely charged ions, so they have very
______ melting points and ______ boiling points.
3. All covalent compounds cannot _____ _______ .
4. All ionic compounds can conduct ________ when they are
_______ or ________ in water.
5. Sugar is a covalent compound but it is soluble in water. State
one test you would use to show that sugar is a covalent
compound.
Contd.
Chemical Bonding
Chapter 7

23. 2323
Quick check 3 (cont.)
6. The table below shows 3 substances.
(a) Which substance is an ionic compound?
(b) Which substance is a metal?
(c) Which substance could be a covalent compound? Solution
Chemical Bonding
Chapter 7
Substance Electrical Conductivity
when solid when molten
A does not conduct does not conduct
B does not conduct conducts
C conducts conducts

24. 2424
1. http://www.quia.com/jq/19617.html
2. http://www.purchon.com/chemistry/bonding.htm
To learn more about Chemical Bonding,
click on the links below!
Chemical Bonding
Chapter 7

25. 2525
1. Covalent compounds have weak forces of attraction between the
molecules, so they have low melting points and low boiling
points.
2. Ionic compounds have very strong forces of attraction between
the oppositely charged ions, so they have very high melting
points and high boiling points.
3. All covalent compounds cannot conduct electricity.
4. All ionic compounds can conduct electricity when they are molten
or dissolved in water.
5. Dissolve some sugar in water, then try to pass electricity through
it. The sugar solution will not able to conduct electricity.
Contd.
Chemical Bonding
Chapter 7
Solution to Quick check 3

26. 2626
Substance Electrical Conductivity
when solid when molten
A does not conduct does not conduct
B does not conduct conducts
C conducts conducts
6. The table below shows 3 substances.
(a) Ionic compound: B
(b) Metal: C
(c) Covalent compound: A
Return
Chemical Bonding
Chapter 7
Solution to Quick check 3 (contd.)

27. 2727
Simple moleculesSimple molecules
 Many covalent substances like water,Many covalent substances like water,
methane, carbon dioxide and iodinemethane, carbon dioxide and iodine
exist as small molecules.exist as small molecules.
 These compounds are said to haveThese compounds are said to have
simple molecular structuressimple molecular structures..
Macromolecular Structures
Chapter 7

28. 2828
MacromoleculesMacromolecules
 Some covalent substances like siliconSome covalent substances like silicon
dioxide (SiOdioxide (SiO22), diamond and graphite are), diamond and graphite are
made up of very large molecules.made up of very large molecules.
 These substances are said to haveThese substances are said to have
macromolecular structuresmacromolecular structures..
Macromolecular Structures
Chapter 7

29. 2929
Properties of MacromoleculesProperties of Macromolecules
 Due to the large structures of these macromolecules,Due to the large structures of these macromolecules,
their chemical and physical properties are differenttheir chemical and physical properties are different
from those of the simple molecules.from those of the simple molecules.
 The macromolecules are solids with very high meltingThe macromolecules are solids with very high melting
and boiling points.and boiling points.
E.g. The melting point of diamond is 3550E.g. The melting point of diamond is 3550 oo
C,C,
compared to 0compared to 0 oo
C for water.C for water.
 Due to their sizes, they are also not as reactiveDue to their sizes, they are also not as reactive
compared to the simple molecules.compared to the simple molecules.
Macromolecular Structures
Chapter 7

30. 3030
Metallic bondingMetallic bonding
 Metals are also made up of very large lattice structures.Metals are also made up of very large lattice structures.
 The metallic structure consists of a lattice of positive ionsThe metallic structure consists of a lattice of positive ions
in a “sea of electrons”.in a “sea of electrons”.
 Metals are malleable because the layers of atoms canMetals are malleable because the layers of atoms can
slide over one another easily as they are being arrangedslide over one another easily as they are being arranged
in neat layers.in neat layers.
Macromolecular Structures
Chapter 7

31. 3131
Properties of Metallic structureProperties of Metallic structure
 The closely packed positively charged metallic ionsThe closely packed positively charged metallic ions
form a lattice structure with the outer electronsform a lattice structure with the outer electrons
moving freely around the whole metallic structure.moving freely around the whole metallic structure.
 The electrostatic attraction between the metallicThe electrostatic attraction between the metallic
ions and the electrons holds the metallic ions tightlyions and the electrons holds the metallic ions tightly
in the lattice and this gives the metal ain the lattice and this gives the metal a highhigh
melting point.melting point.
 The free electrons are able to move andThe free electrons are able to move and
conduct electricity and heat.conduct electricity and heat.
 This explains why metals are goodThis explains why metals are good
conductors of heat and electricity.conductors of heat and electricity.
Macromolecular Structures
Chapter 7

32. 3232
Macromolecular Structures
Chapter 7
Van der Waals Forces
-Van der Waals forces of attraction can exist
between atoms and molecules.
-They are not the same as ionic or covalent
bonds. They arise because of fluctuating
polarities of nearby particles.
-The shape and size of molecules affect the
strength of the van der Waals forces. The
larger the force, the higher the melting and
boiling point.

33. 3333
Structure of diamondStructure of diamond
 In diamond,In diamond, each carbon atom is linked to four othereach carbon atom is linked to four other
carbon atomscarbon atoms by strong covalent bonds.by strong covalent bonds.
 The carbon atoms are arranged in aThe carbon atoms are arranged in a tetrahedraltetrahedral
structurestructure which extends throughout the whole diamondwhich extends throughout the whole diamond
lattice made up of millions of atoms.lattice made up of millions of atoms.
 The diamond structure is very rigid and the bonds areThe diamond structure is very rigid and the bonds are
very strong and difficult to break. This explains whyvery strong and difficult to break. This explains why
diamond isdiamond is very hardvery hard andand strongstrong and has aand has a very highvery high
melting pointmelting point (3550 ºC) and(3550 ºC) and very high boiling pointvery high boiling point
(4827 ºC).(4827 ºC).
Macromolecular Structures
Chapter 7
Structure of
diamond

34. 3434
Structure of graphiteStructure of graphite
 In graphite,In graphite, each carbon atom is linked to three othereach carbon atom is linked to three other
carbon atomscarbon atoms in the same plane by strong covalentin the same plane by strong covalent
bondsbonds.. The carbon atoms form six-member hexagonal rings that link up
to form flat layers.
 The hexagonal rings are arranged in parallel layers with weak
forces of attraction between the atoms in each layer.
Macromolecular Structures
Chapter 7

35. 3535
Properties of graphiteProperties of graphite
 The covalent bonds between the atoms inThe covalent bonds between the atoms in
each layer are strong, and a lot of heat energyeach layer are strong, and a lot of heat energy
is required to break these bonds when graphiteis required to break these bonds when graphite
melts. This explains why graphite has a verymelts. This explains why graphite has a very
high melting point (3652high melting point (3652 oo
C ).C ).
 Not all the electrons in graphite are
used in bonding. There are some free
electrons which enable graphite to
conduct electricity.

strong covalent
bonds
weak forces
The forces of attraction between the atoms in each
layer is weak. The layers can easily slide away from
each other when a force is applied. For this reason,
graphite is smooth and slippery.
Macromolecular Structures
Chapter 7

36. 3636
Summary of propertiesSummary of properties
Macromolecular Structures
Chapter 7
PropertyProperty DiamondDiamond GraphiteGraphite
Hardness andHardness and
TextureTexture
Very hard and strongVery hard and strong Soft, smooth andSoft, smooth and
slipperyslippery
Melting point andMelting point and
Boiling pointBoiling point
Very highVery high Very highVery high
ElectricalElectrical
ConductivityConductivity
Does not conductDoes not conduct
electricityelectricity
Conducts electricityConducts electricity

37. 3737
Uses of diamondUses of diamond
 Due to their differences in properties, diamond andDue to their differences in properties, diamond and
graphite are used in different ways.graphite are used in different ways.
 Diamond being hard and strong, is used for makingDiamond being hard and strong, is used for making
cutting and drilling toolscutting and drilling tools..
 Another use for diamond is for making jewelleryjewellery.
Macromolecular Structures
Chapter 7

38. 3838
Uses of graphiteUses of graphite
 Graphite being smooth and slippery, is used in makingGraphite being smooth and slippery, is used in making
lubricantslubricants for use in machinery, motorcar engines andfor use in machinery, motorcar engines and
even bicycle chains.even bicycle chains.
 Due to its very high melting point, graphite is used as
a heat insulatorheat insulator. It is used to coat the nose of a
space shuttle.
 Graphite being chemically unreactive and a conductorGraphite being chemically unreactive and a conductor
of electricity, is used in makingof electricity, is used in making electrodeselectrodes for use infor use in
electrolysis and in dry cells.electrolysis and in dry cells.
Macromolecular Structures
Chapter 7

39. 3939
Quick check 4Quick check 4
1.The table below shows the properties of 4 substances.
Element Conducts electricity in Melting point
(O
C)Solid state Liquid state
W good good 1085
X poor good 801
Y poor poor 3550
Z poor poor 114
Deduce the type of bonds that each substance has.
Solution
Macromolecular Structures
Chapter 6

40. 4040
Quick check 4 (cont’d)Quick check 4 (cont’d)
2.The pictures below show 4 types of molecular structures.
Identify the substance or the type of bonds shown
by each structure.
A B
C D
Solution
Macromolecular Structures
Chapter 6

41. 4141
Solution to Quick check 4Solution to Quick check 4
1. W: metallic bonding, X: ionic bonding,
Y: macromolecular (diamond), Z: simple molecular
B: silicon dioxide; macromolecular
D: ionic crystal lattice
C: metallic bonding
2. A: graphite; macromolecular
Return
Macromolecular Structures
Chapter 7

42. 4242
• http://mineral.galleries.com/minerals/elements/graphite/graphite.htm
• http://www.chemguide.co.uk/atoms/bonding/metallic.html
To learn more about Macromolecular Structures,
click on the links below!
Macromolecular Structures
Chapter 7

43. ReferencesReferences
 Chemistry for CSEC Examinations by
Mike Taylor and Tania Chung
 Longman Chemistry for CSEC by Jim
Clark and Ray Oliver
4343