Q.Give reasons.
PbCl4 is less stable than PbCl2

Step 1. Recall the inert-pair effect for group 14. Section 9.4.1 explains the state two units below the group oxidation state (+2 for group 14) becomes increasingly stable going down the group, because the outer ns2 pair is poorly shielded by inner d/f electrons.

Step 2. Apply to lead. Lead is the heaviest member of group 14, so this effect is strongest for it — its 6s2 electron pair strongly resists taking part in bonding, making Pb2+ (and hence PbCl2) considerably more stable than Pb4+ (and PbCl4). Problem 9.5 makes the identical point directly. …

Applying the inert-pair-effect explanation from section 9.4.1/Problem 9.5 …

• Explaining this purely in terms of 'lead prefers lower oxidation states' without identifying the actual cause (poor …