In group II B, which metal has greater tendency to form coordination compound?

Question

Question

This question was previously asked in

DSSSB PGT Chemistry (Female) Official Paper (Held On: 06 Jul, 2018 Shift 1)

Answer 1

CONCEPT:

Group IIB Elements and Their Coordination Behavior

Group IIB includes Zinc (Zn), Cadmium (Cd), and Mercury (Hg).
While all form +2 oxidation state, their tendency to form coordination compounds varies due to:
- Atomic size and polarizability
- Softness or hardness of the metal ion
- Type of ligand (hard vs soft)
Hg²⁺ is a soft Lewis acid and forms very stable complexes with soft ligands like CN⁻, S²⁻, and phosphines.
This high affinity for soft ligands makes mercury form more stable and varied coordination compounds than Zn or Cd.

EXPLANATION:

Zinc and cadmium, on the other hand, have smaller atomic radii and do not exhibit such a pronounced tendency to form coordination compounds as mercury does.
Zn²⁺ and Cd²⁺ are hard acids → form weaker complexes with soft ligands.
Hg²⁺ being larger and more polarizable (soft acid) → forms strong coordination complexes especially with soft ligands.
Examples: [Hg(CN)₄]²⁻, [Hg(SCN)₄]²⁻

Therefore, among group IIB elements, mercury (Hg) has the greatest tendency to form coordination compounds, especially with soft ligands.