Worked solutions to textbook questions
Chapter 5 Metals
Q1.
Where would you draw a line in Table 5.1 on page 79 to divide the metals from the
non-metals?
A1.
Between tungsten and carbon
Q2.
a
b
c
d
Potassium is classed as a metal. In what properties is potassium similar to the
metal gold? In what ways is it different?
Identify another element in Table 5.1 that has similar properties to potassium.
Identify another metal in Table 5.1 that has similar properties to gold.
Where are these four metals in the periodic table?
A2.
a
b
c
d
Both potassium and gold have good thermal and electrical conductivity.
However, gold has a higher density, and higher melting and boiling temperatures
than potassium.
sodium
silver, copper
Sodium and potassium are in group 1. Gold, silver and copper are transition
metals.
Q3.
a
b
Which metals would you select if you wanted a good electrical conductor?
What other factors not listed here might influence your choice?
A3.
a
b
silver, copper, gold, aluminium
Availability and cost need to be considered; also properties such as malleability
and ductility.
Q4.
Suggest some properties not included in Table 5.1 on page 79 that you would need to
consider before choosing between aluminium and iron for building a bridge.
A4.
tensile strength, cost, availability
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Worked solutions to textbook questions
Q5.
The properties of calcium mean that it is also classed as a metal.
a Draw a diagram to represent a calcium metal lattice.
b Describe the forces that hold this lattice together.
A5.
a
b
Strong electrostatic forces of attraction between Ca2+ ions and the delocalised
valence electrons.
Q6.
Barium is an element in group 2 of the periodic table with a melting temperature of
850°C and conducts electricity in the solid state. Describe how the properties of
barium can be explained in terms of its bonding and structure.
A6.
Barium has a high melting temperature because there are strong attractive forces
between the positive ions and the delocalised electrons. Barium conducts electricity
because the delocalised electrons from the outer shell are free to move.
E1.
How many electrons are there in:
a an atom of cobalt?
b a cobalt ion with a charge of +2?
c a cobalt ion with a charge of +3?
AE1.
a
b
c
27
25
24
E2.
Write the electronic configuration of a Zn2+ ion.
AE2.
1s22s22p63s23p63d10
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Q7.
Consider the following alloys: a 50-cent coin, carbon steel.
a List the elements present.
b Draw a diagram to show how the atoms of these elements are arranged in the
alloy.
A7.
a
b
50-cent coin: nickel and copper atoms; carbon steel: iron and carbon atoms
Q8.
Dentists fit partial dentures by means of small metal hooks, which attach the denture
to the remaining teeth. The hooks are easily bent at first to fit snugly in individual
mouths. If these hooks are bent backwards and forwards too often, however, they
become brittle and snap. Can you explain what happens?
A8.
The metal in the hooks becomes work-hardened and brittle.
Chapter review
Q9.
Look at groups 1–18 of the periodic table.
a Which groups contain metals only?
b Which groups contain a mixture of metals and non-metals?
A9.
a
b
1 and 2
13, 14, 15 and 16
Q10.
Which of the following metals would have similar properties to beryllium?
Ca, Cs, Cu, Pb, Mg, Zn, Sr, K
A10.
Mg, Ca, Sr
Q11.
Which of the following elements are metals?
boron, caesium, titanium, strontium, selenium, bismuth, tellurium, francium
A11.
caesium, titanium, strontium, bismuth, francium
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Worked solutions to textbook questions
Q12.
Look at the periodic table on page 408.
a Name a metal that would have similar properties to calcium.
b In which part of the periodic table are magnetic metals found?
A12.
a
b
magnesium, strontium or barium
transition series
Q13.
a
b
c
What is the relative atomic mass of aluminium?
Calculate the mass of 3.25 mol of aluminium.
What mass of silver would contain the same number of silver atoms as there are
aluminium atoms in 500 g of aluminium?
A13.
a
b
c
27.0
m = nM
m(Al) = 3.25 mol × 27.0 g mol–1
= 87.8 g
m
n=
M
n(Al atoms) =
500
= 18.5 mol
27.0
m = nM
m(Ag) = 18.5 mol × 107.9 g mol–1
= 2.00 × 103 g (2.00 kg)
Q14.
A bracelet is known to contain 22 g of gold.
a What is the relative atomic mass of gold?
b How many atoms of gold would be present in the bracelet?
A14.
a
197.0
b
Use the formulas: N = n × NA, where NA = 6.02  1023, and n =
m
, where m is
M
the mass in grams, n the amount of substance in mol and M the molar mass.
22
n(Au) =
= 0.112 mol
197.0
Number of Au atoms = 0.112 × 6.02  1023 = 6.7  1022 atoms
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Q15.
Use the data in Table 5.1 on page 79 to answer the following questions:
a Which metal is the best conductor of heat?
b Why is this metal not used in saucepans?
c What metals are used to make saucepans?
A15.
a
b
c
silver
It is too expensive and tarnishes readily.
aluminium, copper (combined with stainless steel)
Q16.
Use Table 5.1 on page 79 to answer the following questions:
a Why is tungsten a suitable metal to use in the filament of an incandescent light
globe?
b Which metal would be the most suitable for building aircraft? Why?
c Which metal is a liquid at room temperature?
A16.
a
b
c
Tungsten has a high melting temperature; its conductivity is not very high, that is,
it has a reasonably high resistance.
aluminium, because of its relatively low density
mercury
Q17.
Use the data in Table 5.1 on page 79 to answer the following questions:
a Which metal has the strongest forces of attraction between its metal ions and its
delocalised electrons?
b Why is that metal not used in place of aluminium in aircraft manufacture?
c Which metal has the lowest density?
d Why is the metal not used in making aircrafts?
A17.
a
b
c
d
tungsten
too dense or heavy
potassium
too reactive, especially in air and water
Q18.
What do you think is the most important property of each of the following metals that
has led to its widespread use?
a aluminium
b copper
c iron
A18.
a
b
c
low density
high electrical conductivity
high tensile strength
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Q19.
Metals have many uses in modern society.
a i Name one metal that is used in large quantities in the building industry.
ii What properties of the metal make it suitable for this use?
iii What properties limit its use in buildings?
b i Name one metal that is used in large quantities for making electrical wires.
ii What properties of this metal make it suitable for use in wires?
c i Name two metals that are used in large quantities in the jewellery trade.
ii What properties of these metals make them suitable for this use?
A19.
a
b
c
i
ii
iron (steel) or aluminium
Iron and steel are strong. Aluminium has a low density (light) and can be
easily coloured.
iii Iron rusts easily. Aluminium is soft and lacks strength.
i copper
ii good conductor of electricity and is ductile
i gold, silver and platinum
ii non-reactive, malleable and ductile, lustrous
Q20.
Use the metallic bonding model to explain each of the following observations:
a Copper wire transmits electricity.
b A metal spoon used to stir a boiling mixture becomes too hot to hold.
c Iron has a high melting temperature, 1540°C.
d Lead has a density of 11.4 g mL–1, which is much higher than a non-metal such as
sulfur.
e Copper can be drawn out in the form of a wire.
A20.
a
b
c
d
e
When a current is applied to the copper wire, the free-moving, delocalised
electrons move from one end to the other and so the copper wire conducts
electricity.
The delocalised electrons in the metal spoon obtain energy from the boiling
mixture and move more quickly. These electrons move freely throughout the
spoon, colliding with other electrons and metal ions, transferring energy so that
the spoon becomes warmer and, eventually, too hot to hold.
A lot of energy is required to overcome the strong forces of attraction between
the iron ions and the delocalised electrons in the metal lattice, so that the iron
changes from a solid to a liquid.
Because of the strong forces of attraction between them, the lead ions and the
delocalised electrons form a closely packed three-dimensional structure. Also, the
lead atom itself has a higher mass-to-volume ratio than the sulfur atom. This
means that the density—the mass per volume—is high.
As the copper is drawn out, the copper ions are forced apart and the delocalised
electrons rearrange themselves around these ions and re-establish strong forces of
attraction.
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Q21.
Alloys are modified metals. In each example, state the metals used and one property
that is different from the original metals.
a an Australian 20-cent coin
b solder
c 9-carat gold
d stainless steel
e brass
f dental mercury amalgam
A21.
a
b
c
d
e
f
copper and nickel; harder, more corrosion resistant and a silver colour
tin and lead; lower melting temperature
gold, silver and copper; harder
iron, nickel and chromium; resists rusting, stronger
copper and zinc; harder, stronger and resists corrosion
mercury and zinc (sometimes a little silver is added); harder, non-toxic
Q22.
Draw your own concept map, using the following terms: metal, cation, delocalised
electron, lattice, electrostatic attraction.
A22.
A variety of answers is possible. An example of a possible answer is shown.
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Q23.
Some metals are found as elements in nature; others are found as compounds,
combined with other elements, such as oxygen and sulphur, in ores. Australia has
natural reserves of many metals and ores, with mining producing large quantities of
metals, including aluminium, copper, gold, iron and silver.
a Give the chemical symbol for each of these metals.
b In which group, period and block of the periodic table are each of these metals
found?
c Which of these metals are found in nature as elements rather than compounds?
d Which of these metals are transition elements?
e Which of these elements is the rarest?
A23.
a
b
c
d
e
aluminium Al, copper Cu, gold Au, iron Fe, silver Ag
aluminium: period 3, group 13, p-block
copper: period 4, 1st transition series, d-block
gold: period 6, 3rd transition series, d-block
iron: period 4, 1st transition series, d-block
silver: period 5, 2nd transition series, d-block
gold and silver
copper, gold, iron and silver
gold
Q24.
It has been shown using X-rays that metals occur as crystals.
a Explain, using the metallic bonding model, why metals form crystals.
b What problems can this crystalline structure of metals cause?
A24.
a
b
The positive ions are arranged in a regular, three-dimensional lattice.
Stress corrosion cracking can occur between the crystal grains.
Q25.
Do you think ‘Liquidmetal’ is an appropriate name for the material described on
page 89? Give reasons for your answer.
A25.
It is an appropriate name in terms of the lack of the regular, crystalline structure that is
generally associated with metals. However, there are other amorphous solids and they
are not classified as liquids because, overall, their properties do not fit the model of a
liquid.
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Q26.
a
b
c
Which metals are used in greatest quantities today?
For what purposes are they used?
How does the usage of metals today differ from that of 100 years ago?
A26.
Think about the metals you see around your house, your means of transport, your
town or suburb.
a iron, aluminium, copper
b buildings, bridges, transport
c Aluminium was not available 100 years ago. Many alloys are now available.
Q27.
Aluminium is the most abundant metal in the Earth’s crust. Why was aluminium not
available before 1886?
A27.
Aluminium is extracted from its ore by electrolysis. There was no source of electricity
available for this process until 1886.
Q28.
Titanium is a comparatively abundant metal in the Earth’s crust and Australia has
large reserves of this metal. It is used increasingly in our technological society. Find
out:
a where titanium is mined in Australia
b the main uses of titanium
c the properties of titanium that make it useful for those purposes
A28.
a
b
c
Titanium is mined in the south-western coastal region of Western Australia and
the central eastern coast of Australia (Newcastle to Brisbane).
Titanium is alloyed with aluminium in aircraft and spacecraft, and is also used in
spectacle frames for people with acidic skin, which stains regular frames green.
TiO2 is used as a white pigment in paints.
Titanium is very strong and has a relatively low density.
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