Taylor High School
Chemical Changes and Structure
Bonding
Homework Exercises
Atomic Structure and bonding related to properties of
materials SCN 4-03a
Covalent and Ionic Bonding
1. In which of the following compounds are the atoms held together by
covalent bonds?
Sodium chloride
Water
Carbon dioxide
Sulphur dioxide
Boron hydride
Calcium carbonate
Carbon tetrafluoride
Lithium fluoride
Aluminium oxide
Magnesium bromide
2. The following diagram shows how the atoms are held together in a
molecule of chlorine:
a) What is the chemical formula of chlorine?
b) What is the electron arrangement for each atom of chlorine before
the covalent bond is formed?
c) Explain why each atom of chlorine reacts and forms a covalent bond
with another atom.
3. Copy and complete the diagram below to show what holds the atoms
together in a covalent bond.
Negative __________
Positive
nucleus
_________ force of attraction
4. Copy the sentence below and circle the correct words.
5. The table lists the names of some elements.
(a) Identify the two elements which exist as diatomic molecules.
(b) Explain the meaning of the word diatomic.
6. Write the names and chemical formula of the 7 diatomic elements.
7. Use the word bank below to answer the following questions
Oxygen
Carbon
Nitrogen
Fluorine
Argon
Magnesium
Identify the element
a) which forms 2 covalent bonds between its atoms.
b) which forms 3 covalent bonds between its atoms.
c) which does not form bonds because it has a stable electron
arrangement.
8. The diagram below shows the arrangement of electrons in a molecule of
hydrogen chloride.
Draw similar diagrams to show how the outer electrons are arranged in the
following molecules
a)
b)
c)
d)
e)
nitrogen hydride (NH3)
carbon tetrafluoride (CF4)
hydrogen sulphide (H2S)
hydrogen oxide (H2O)
carbon dioxide (CO2)
9. The chemical formula for a molecule of methane is CH4.
a) Draw an outer electron diagram to show how these atoms combine
to form the methane molecule.
b)What is the term used to describe the shape of this molecule?
10. Draw and name the shape of each of the following molecules.
a)
CCl4
b)
NH3
e)
NCl3
f)
HCl
c)
H 2O
d)
SiH4
11. Match the word to the statement
Molecule
the ratio of atoms of each element in the substance
Covalent bond
a group of atoms joined together
Chemical formula
attraction between the positive nuclei and shared
electrons
12. Which of the following compounds are ionic?
Aluminium chloride
Silicon oxide
Nitrogen dioxide
Phosphorous chloride
Magnesium iodide
Calcium oxide
13. Copy and complete the table
Atom symbol
Na
Atom electron
arrangement
2)8)1
Ion symbol
Na+
Ion electron
arrangement
2)8
K
2)8)2
2)8)8)2
Al
O
ClN314. Explain why the noble gases do not form ions.
15. Identify the compound from the following list in which both ions have
the same electron arrangement as argon.
Strontium chloride
Barium fluoride
Lithium oxide
Sodium fluoride
Calcium oxide
Potassium chloride
16. Magnesium has the electron arrangement 2, 8,2 It forms an ion as
shown below
+ 2e-
2,8,2
2,8,
The magnesium atom gets a more
stable electron arrangement by
giving away two electrons to form
a magnesium 2+ ion
a) Write the electron arrangements for
i) a sodium atom ii) a chlorine atom
b) copy and complete the diagram below to show how a chlorine atom forms
an ion.
+ e-
2,8,8
2,8,7
c) Use target pictures and electron arrangements to show how
a sodium atom forms an ion.
d) What is meant by the term ionic lattice?
17. Use the following to answer the questions below…
NaCl(aq)
HCl (g)
KF(s)
CCl4(l)
MgCl2(l)
SiO2(s)
Identify the substance(s) which
a) do not conduct electricity
b) always conducts electricity due to free moving ions
18. a) Why do ionic compounds like lead iodide not conduct electricity
when solid?
b) Explain what is meant by the term ionic bond.
19. Copy the passage and delete the incorrect phrases:
Ionic substances conduct / do not conduct electricity in solid form
because the ions are/ are not free to move. However ionic compounds
conduct / do not conduct electricity when molten or in solution because
the ions are/ are not free to move.
20. The table contains information about some substances.
Substance
A
B
C
D
E
Melting point
(0C)
639
2967
159
1402
27
Boiling Point
(0C)
3228
3273
211
2497
677
Conducts as
a solid
Yes
No
No
No
Yes
Conducts as
a liquid
No
No
No
Yes
Yes
a) Identify the substance which exists as a covalent network.
b) Identify the substance which could be calcium fluoride.
c) Identify the substance which exists as covalent molecules.
21. The dead sea is a pool that was left behind after a sea had evaporated
over many centuries. The following table gives average values of some ion
concentrations in water samples from the open sea and the dead sea (In gl-1).
Ion
Na+
ClMg2+
SO42Ca2+
Concentration
10.5
19.0
1.5
2.5
0.5
30.0
160.0
40.0
0.5
10.0
of ion in Sea
water (gl-1)
Concentration
of ion in Dead
sea (gl-1)
a) Use a suitable scale to draw a bar graph for the concentration of
ions in water from the Dead sea.
b) Which ion is more concentrated in sea water than in the Dead sea?
22. Peter tested the conductivity of molten sodium chloride, hexane (C6H14)
and water.
a) Draw the apparatus that Peter would have used to test the conductivity
of the samples.
b) Explain why hexane will not conduct electricity.
c) Peter also tested solid sodium chloride and found that this did not conduct
electricity.
Explain why sodium chloride conducts electricity when molten but not when
solid.
23. A student investigated how the concentration of sodium chloride in water
affected the freezing point.
(a) What type of bond is broken in sodium chloride when it dissolves
in water?
(b) The table shows information about the freezing point of
different sodium chloride solutions.
Concentration of sodium chloride
solution (moll-1)
Freezing point (oC)
0
0.1
0.2
0.3
0.4
0.5
0
-0.2
-0.5
-0.8
-1.1
-1.5
i) Draw a graph of concentration of sodium chloride against freezing
point.
ii) Describe the relationship between the concentration and freezing
point.
iii) Predict the freezing point of a 0.6moll-1 solution of sodium chloride.
24. Write ionic formula for the following:
a) sodium chloride
c) potassium bromide
e) barium carbonate
g) aluminium sulphate
b) magnesium oxide
d) zinc (II) sulphide
f) lithium hydroxide
25. The colour of some compounds is shown in the table below.
Compound
cobalt chloride
iron (III) sulphate
nickel (II) chloride
sodium chloride
sodium manganate (VII)
sodium sulphate
iron (III) chloride
potassium chloride
potassium manganate (VII)
Colour
red
brown
green
colourless
purple
colourless
brown
colourless
purple
Using the information from the above list, suggest possible colours
for the following ions.
(a) Cobalt (II) ion, Co²+
(b) Iron (III) ion, Fe³+