Question

The second ionization energy is maximum for:

• A. Boron
• B. Beryllium
• C. Magnesium
• D. Silicon

Answer 1

The correct option is A Boron

The ionization energy increases for atoms or ions which already has a stable electronic configuration.
The electronic configuration of
$B^{+}\to 1s^{2}2s^2$
$B{e}^{+}\to 1s^{2}2s^1$
$M{g}^{+}\to 1s^{2}2s^{2}2p^{6}3s^1$
$S{i}^{+}\to 1s^{2}2s^{2}2p^{6}3s^{2}3p^1$
So, in $B^{+}$ the electron is to be removed from completely filled s-subshell, which is difficult. Thus, the second ionization energy of boron is maximum.