Group VII elements (Halogens)

Question 1

Define halogens

Answer 1

• group vii
• non-metals
• exist as diatomic covalent molecules

Question 2

Physical properties

Answer 2

• low mp&bp
• coloured
• room temp:
• F2, Cl2 gas
• Br2 liquid
• I2 solid

Question 3

How physical properties change down the group

Answer 3

• mp & bp increase

- colours become darker

Question 4

Halogens’ reactivity

Answer 4

• reactive
• each has 7 valence electrons
• only 1 more needed to achieve stable octet/electronic configuration
• react with most metals to form salts called halides

Question 5

Chemical rxns

Answer 5

1. Displacement rxns with halide solns

2. Powerful OA

Question 6

Displacement rxn with halide soln

Answer 6

• more reactive halogen displaces less reactive halogen from halide solution
• e.g. Cl (aq) + 2NaBr (aq) –> 2NaCl (aq)+ Br2 (aq)
• sodium bromide: colourless

Question 7

Reactivity of halogens

Answer 7

• decreases down grp
• size of atom increases
• more difficult for nucleus to attract 1 more electron

Question 8

Halogens are powerful OA

Answer 8

• atoms of halogen readily gain electrons to form halide ions (-1)
• e.g. Cl2 + 2e- –> 2Cl-
• easily gains e-, reduced