Question

Among the following, the incorrect order is:

• A. $I.E_2\left(N\right)>I.E_2\left(O\right)$
• B. $I.E_2\left(O\right)>I.E_2\left(N\right)$
• C. $I.E_1\left(O\right)<I.E_1\left(N\right)$
• D. $I.E_2\left(Li\right)>I.E_2\left(Be\right)$

Answer 1

The correct option is A $I.E_2\left(N\right)>I.E_2\left(O\right)$

$I.E_2\left(Li\right)>I.E_2\left(Be\right)$
$\because$ An electron has to be removed from a stable $1s^2$ configuration in $L{i}^{+}$ ion.

${}_7\left[N\right]:1s^{2}2s^{2}2p^3$
${}_8\left[O\right]:1s^{2}2s^{2}2p^4$
$\therefore I.E_1\left(O\right)<I.E_1\left(N\right)$ because electron has to be removed from a stable half-filled configuration in $N$ atom.

$\left[N^{+}\right]:1s^{2}2s^{2}2p^2$
$\left[O^{+}\right]:1s^{2}2s^{2}2p^3$
$\therefore I.E_2\left(O\right)>I.E_2\left(N\right)$, Since $O^{+}$ has a half-filled configuration, obviously it is more stable and has a greater ionisation energy than $N^{+}$.