Chemical Properties of Group 7

Question 1

Halogens react with metals by

Answer 1

accepting an electron from the metal atom to become an ion with 1- charge
Eg. Ca (s) + Cl2 (g) → CaCl2 (s) consisting of Ca2+ and 2Cl- ions

Question 2

Halogens are therefore oxidising agents:

Halogens oxidise the metal by…..

Halogens become reduced as they…

Answer 2

the metal by removing an electron from the metal (the oxidation number of the metal increases)

become reduced as they gain an extra electron from the metal atom (the oxidation number of the halogen decreases

Question 3

The oxidising power of the halogens ………….. going down the group (the halogens get …….reactive)

Answer 3

decreases

less

Question 4

The oxidising power of the halogens decreases going down the group (the halogens get less reactive)

This can be explained by looking at their electronegativities

Answer 4

The decrease in electronegativity is linked to the size of the halogens

Going down the group, the atomic radii of the elements increase which means that the outer shells get further away from the nucleus

An ‘incoming’ electron will therefore experience more shielding from the attraction of the positive nuclear charge

The halogens’ ability to accept an electron (their oxidising power) therefore decreases going down the group

Question 5

The reactivity of halogens is also shown by their displacement reactions with other halide ions in solutions
A more reactive halogen can displace a

Answer 5

less reactive halogen from a halide solution of the less reactive halogen
Eg. The addition of chlorine water to a solution of bromine water:
Cl2 (aq) + 2NaBr (aq) → 2NaCl (aq) + Br2 (aq)

The chlorine has displaced the bromine from solution as it is more reactive which can be summarised in the following ionic equation:
Cl2 (aq) + 2Br- (aq) → 2Cl- (aq) + Br2 (aq)

Question 6

Halide Ions: Reducing Agents
Halide ions can also act as……..and donate electrons to another atom

Answer 6

reducing agents

Question 7

The halide ions themselves get oxidised and lose electrons

The reducing power of the halide ions ………….going down the group

due to

Answer 7

increases

by looking at the ionic radii of the halide ions

Question 8

Why does ionic radius affect reducing power

Answer 8

Going down the group, the halide ions become larger

The outermost electrons get further away from the nucleus

The outermost electrons also experience more shielding by inner electrons

As a result of this, the outermost electrons are held less tightly to the positively charged nucleus

Therefore, the halide ions lose electrons more easily going down the group and their reducing power increases

Question 9

Halogen is a derived from a greek word meaning salt-maker, a good reminder of their reaction with metals to form salts.