JEE Chemistry 2024 Question with Solution

Given: Statements A, B, C, and D about Zn, Cd, and Hg are to be checked.

Find: Which statements are correct.

Evaluate each statement using the known properties of group $12$ elements:

1. Statement A: Zn, Cd, and Hg have completely filled $d$-subshells, but because of this they show lower enthalpy of atomization than typical transition metals, not high enthalpy of atomization. So A is incorrect.

2. Statement B: Zn and Cd generally show only the $+2$ oxidation state, while Hg can show $+1$ and $+2$ oxidation states. So B is correct.

3. Statement C: The compounds of $\text{Zn}^{2+}$, $\text{Cd}^{2+}$, and $\text{Hg}^{2+}$ are typically diamagnetic because their $d$-subshells are fully filled. So C is incorrect.

4. Statement D: Zn, Cd, and Hg are regarded as soft metals. So D is correct.

Therefore, the correct statements are B and D only. Hence, the correct option is A.

Given: Four statements about Zn, Cd, and Hg.

Find: The correct combination.

• A is incorrect because these elements have fully filled $d$-orbitals and comparatively weaker metallic bonding than typical transition elements, so their enthalpy of atomization is not high.
• B is correct because Zn and Cd usually remain in the $+2$ state, whereas Hg can exist in $+1$ and $+2$ states.
• C is incorrect because the common ions $\text{Zn}^{2+}$, $\text{Cd}^{2+}$, and $\text{Hg}^{2+}$ have filled $d$-orbitals and are therefore diamagnetic, not paramagnetic.
• D is correct because these are classified as soft metals.

So the correct set is B, D only, which matches option A. The solution saying 'The Correct Option is A' is consistent with the statement-wise conclusion.