Which of the following statements are correct about Zn, Cd and Hg ?
A. They exhibit high enthalpy of atomization as the d-subshell is full.
B. Zn and Cd do not show variable oxidation state while Hg shows +I and +II.
C. Compounds of Zn, Cd and Hg are paramagnetic in nature.
D. Zn, Cd and Hg are called soft metals.
Choose the most appropriate from the options given below:

Solution

Chemistry ma’am · 2 steps

A full d¹⁰ shell means weak metallic bonding and no unpaired electrons: test each statement on that.

1. Start from d10. Zn, Cd and Hg have the configuration (n-1)d¹⁰ns². Their d-subshell is full in the atom and stays full in the common +2 state. So the d electrons do not take part in metallic bonding, and there are no unpaired electrons.

   Statement	What really happens	Verdict
   A. High enthalpy of atomization	Only the two ns electrons form metallic bonds, so bonding is weak. Zn has the lowest atomization enthalpy in the 3d series, and Hg is a liquid.	Wrong
   B. Zn, Cd fixed; Hg shows +1 and +2	Zn and Cd show only +2. Hg shows +2 and also +1, as the dimer ion Hg₂²⁺ in Hg₂Cl₂.	Correct
   C. Compounds are paramagnetic	All the ions are d¹⁰ with no unpaired electrons. Hg₂²⁺ pairs its 6s electrons in the Hg–Hg bond. So the compounds are diamagnetic.	Wrong
   D. Soft metals	Weak metallic bonding makes them soft, with low melting points.	Correct

2. So. Only B and D are correct, which is option (d).

The idea to keep. For Zn, Cd and Hg, the full d-subshell sits idle. It does not bond, so the metals are soft with low atomization enthalpy. It has no unpaired electrons, so their compounds are diamagnetic.

Answer from the NTA final answer key. Solution by PrepWiser.