C2.2 - Bonding

Question 1

How did Mendeleev order his periodic table? (1)

Answer 1

increasing atomic mass

Question 2

Describe metallic bonding and explain why metals are good conductors of electricity. You may wish to draw a labelled diagram. (3)

Answer 2

idea of (close packed) positive metal ions (1)

idea of electrons dispersed between ions/ sea of electrons/ delocalised electrons (1)

electrons can move/ carry the current (1)

Question 3

An element X has the electronic structure 2.8.8.2.
Explain how you can tell that element X is calcium. (1)

Answer 3

either one:
element has 20 electrons and on periodic table element 20 is calcium (1)

element is in group 2 and period 4 (same as calcium) (1)

Question 4

Amir is making a cake.
He adds baking powder to the cake mixture.
Baking powder contains sodium hydrogencarbonate.
Sodium hydrogencarbonate breaks down when heated in an oven.
Sodium carbonate, water and a gas are the products made.
What gas is made? (1)

Answer 4

carbon dioxide

Question 5

Sodium chloride is an ionic compound. Sodium chloride
• will not conduct electricity when it is a solid
• will conduct electricity when it is dissolved in water.
Explain these two observations in terms of structure and bonding. (2)

Answer 5

solid - ions are not free/ cannot move/ held in lattice/ in a giant ionic structure (1)

dissolved - ions can move (around each other) (1)

Question 6

Graphite is used to make pencil leads.
Explain why the properties of graphite make it suitable for pencil leads. (2)

Answer 6

slippery/ layers can slide over one another (1)

(black or grey so) can be easily seen on paper (1)

Question 7

Explain why graphite has a high melting point. (2)

Answer 7

graphite is arranged in giant covalent lattice/ has many covalent bonds (1)

(so) bonds need lots of energy to be broken (1)

Question 8

Graphene contains one layer of carbon atoms.
Graphene is made from graphite.
Graphene is harder than graphite.
Explain, using ideas about structure and bonding, why graphene is hard and graphite is slippery. (2)

Answer 8

graphene only contains strong covalent bonds (1)

graphite contains weak bonds between the layers (1)

Question 9

iron: high density, low conductivity, high relative strength, low cost per tonne
aluminium: low density, high conductivity, low relative strength, high cost per tonne
The power company makes the power lines from iron surrounded by aluminium. Explain why the power company makes power lines from iron and aluminium. Use information in the table.

Answer 9

aluminium is good conductor of electricity/ aluminium has low density (1)

aluminium is not strong enough on its own so has to be supported by iron (1)