Question

Which of the following has maximum first ionisation enthalpy?

• A. Ti
• B. Mn
• C. V
• D. Ni

Answer 1

The correct option is D Ni

Across a period, the number of protons in the nucleus increases, due to which, the effective nuclear charge also increases and thus, it is difficult to remove an electron from the outermost shell. Hence, more ionization enthalpy is needed to remove an electron and the maximum first ionization enthalpy will be for Ni whose outermost electronic configuration is $3d^{8}4s^2$ and it will be quite hard to extract an electron by overcoming the effective nuclear charge.
Hence, option (d) is correct.