Question

Assertion (A) First ionisation enthalpy of $Cr$ is lower than that of $Zn$.
Reason (R) $IE$ of $Cr$ is lower due to the stability of $d^{5}$.

• A. Both $A$ and $R$ are correct; $R$ is the correct explanation of $A$.
• B. Both $A$ and $R$ are correct; $R$ is not the correct explanation of $A$.
• C. $A$ is correct; $R$ is incorrect.
• D. $R$ is correct; $A$ is incorrect.

Answer 1

Answer: (A)

First ionisation enthalpy of $Cr$ is lower than that of $Zn$ because ionisation enthalpy of $Cr$ is lower due to the stability of $d^{5}$ by losing one electron from outer $s$-orbital and the value for $Zn$ is higher due to stable $d^{10} s^{2}$ configuration.