Question

Assertion :1${}^{st}$ ionisation potential of mercury is greater than cadmium. Reason: Hg has stable electronic configuration (5d${}^{10}$6s${}^2$).

• A. Statement - I is True, Statement-II is True ; Statement-II is a correct explanation for Statement-I
• B. Statement-I is True, Statement-II is True ; Statement-II is NOT a correct explanation for Statement-I
• C. Statement-I is True, Statement-II is False.
• D. Statement-I is False, Statement-II is True.

Answer 1

The correct option is B Statement-I is True, Statement-II is True ; Statement-II is NOT a correct explanation for Statement-I

Both statements are true,
Assertion : 1${}^{st}$ ionisation potential of mercury is greater than cadmium.
Reason: Hg has stable electronic configuration (5d${}^{10}$6s${}^2$).

But Cadmium also has $4d^{10}5s^2$ configuration, same as that of $Hg$. Hence the reason does not explain the assertion.
However this is due to higher effective nuclear charge, due to increase in number of protons in nucleus, as Hg, comes after Lanthanoid series.