Bonding

Question 1

(ii) Sodium chloride has a melting point of 801 °C.

Explain why the melting point of sodium chloride is high.

Answer 1

An explanation linking two of
• strong (electrostatic) forces of
attraction
• between oppositely charged
ions
• so requires lot of heat/energy
to overcome forces/break
bonds

Question 2

*(b) Magnesium has an electronic configuration of 2.8.2.
Oxygen has an electronic configuration of 2.6.
Explain, in terms of their electronic configurations, how magnesium and oxygen
atoms react to form the ionic compound magnesium oxide, MgO, and include a
description of the structure of solid magnesium oxide.
(6)

Answer 2

A description including some of the following points
ion formation
• magnesium atoms lose electrons
• each magnesium atom loses two electrons
• to acquire full outer shell
• magnesium (configuration) becomes 2.8
• forms Mg2+ ion
• electrons transferred to oxygen atoms
• oxygen atoms gain electrons
• each oxygen atom gains two electrons
• oxygen (configuration) becomes 2.8
• to acquire full outer shell
• forms O2- ion
structure
• magnesium ions attract oxide ions
• due to opposite charges
• ions pack close together
• ratio of ions 1: 1
• ions arranged in lattice
• giant (ionic) (structure)

Question 3

(i) State the maximum number of covalent bonds formed by a carbon atom in a
diamond crystal.
(1)

Answer 3

4

Question 4

(iii) Explain, in terms of its structure, why graphite is able to be used as a lubricant.
(2)

Answer 4

An explanation linking
 layers can slide / move/slip
(over each other) (1)
 (because)weak forces between
layers (of atoms) (1)

Question 5

*(c) Sodium chloride and water have very different properties.
Sodium chloride is an ionic substance.
It is a crystalline solid at room temperature.
It has a high melting point.
It conducts electricity when molten or in aqueous solution.
Water is a covalent substance.
It is a liquid at room temperature.
It is a very poor conductor of electricity.
Explain these properties of sodium chloride and water in terms of the particles
present and the forces between them.
(6)

Answer 5

Sodium chloride
 contains {charged particles/ ions}
 contains Na+ and Cl-
 (regular) giant structure/lattice (hence crystalline)
 strong (electrostatic) forces (of attraction) between
{ions/particles}/ strong bonds between
{ions/particles}/strong ionic bonds
 a lot of (heat) energy is needed to separate the
{ions/particles}/ a lot of (heat) energy is needed to
{overcome/ break } the {forces/ bonds/ lattice} (hence
high melting point)
 {ions/ charged particles} free to move (so it conducts
electricity) when molten/ dissolved in water
Water
 covalent bonds between (hydrogen and oxygen) atoms/
(pair of) electrons shared between atoms
 contains molecules
 H2O
 simple molecular/ simple covalent
 weak intermolecular forces/ weak {forces/ bonds}
between {molecules/ particles}
 not much energy needed to separate the {molecules/
particles}/ not much energy is needed to break the
{forces/ bonds between particles} (hence liquid at room
temperature)
 does not contain any charged particles/ ions/ {delocalised/
free} electrons (hence does not conduct electricity)

Question 6

Oxygen has a low boiling point because there are…

Answer 6

weak forces of attraction between the oxygen molecules

Question 7

c) Another gas present in air is carbon dioxide, CO2
.
There are covalent bonds between the atoms in a molecule of carbon dioxide.
(i) Describe what is meant by a covalent bond.

Answer 7

An description including
• shared (electrons) (1)
• pair(s) of electrons (between
atoms) (1)

Question 8

(ii) The electronic configuration of oxygen (atomic number 8) is 2.6.
Give the electronic configuration of carbon (atomic number 6).

Answer 8

2.4

Question 9

Sodium sulfide is an ionic compound.
Describe, in terms of electron transfer, how sodium atoms react with sulfur atoms
to form sodium sulfide.
Your description should include the charges on the ions formed.

Answer 9

sodium - 2.8.1 / 1 electron in
outer shell (1)
sodium (atoms) lose electrons
(1)
one per atom (1)
(forms) Na+ (1)
sulphur - 2.8.6 / 6 electrons in
outer shell (1)
sulfur (atoms) gain electrons (1)
two per atom (1)
(forms) S2- (1)
two sodium atoms / ions combine
with one sulfur atom / ion (1)
formula is Na2S (1)