Question

(a)Which has the larger third ionisation energy, Be or N?
(b) Which has the larger fourth ionisation energy, Ga or Ge?

• A. (a) Be (b) Ge
• B. (a) Be (b) Ga
• C. (a) N (b) Ga
• D. None of these

Answer 1

The correct option is B (a) Be (b) Ga

$B{e}^{2+}-1s^2$
$N^{2+}-1s^{2}2s^{2}3s^1$
Since the configuration of $B{e}^{2+}$ is that of noble gas and very stable it will require very high energy to remove one more electron from $B{e}^{2+}$.
$G{a}^{3+}-\left[Ar\right]3d^{10}$
$G{e}^{3+}-\left[Ar\right]3d^{10}4s^1$
$G{a}^{3+}$ doesn't have any unpaired electron whereas $G{e}^{3+}$ has one unpaired electron in $4s$ orbital it will be more easier for $G{e}^{3+}$ to loose an electron.