Question

A halogen of low atomic number can oxidise halide ions of higher atomic numbers. Comment on the statement and explain with suitable examples.

Answer 1

1. Halogens act as oxidising agents because they gain electrons to form halide ions.
2. Oxidising power decreases down the group, fluorine > chlorine > bromine > iodine.
3. Therefore, a halogen with a lower atomic number can oxidise halide ions of higher atomic numbers.
4. For example, fluorine (F₂) can oxidise chloride (Cl⁻), bromide (Br⁻), and iodide (I⁻) ions.
   \[\ce{F2 + 2⁢X- -> 2⁢F- + X2}\], (X = Cl, Br, I)
5. Similarly, Chlorine (Cl₂) oxidises bromide and iodide ions; Bromine (Br₂) oxidises iodide ions. 
   \[\ce{Cl2 + 2⁢X- -> 2⁢Cl- + X2}\], (X = Br, I)
   \[\ce{Br2 + 2⁢I- -> 2⁢Br- + I2}\]
6. This shows a halogen can displace halide ions of halogens below it in the group from their salt solutions.

Thus, halogens with lower atomic numbers are stronger oxidising agents and can oxidise halide ions of halogens with higher atomic numbers.