Question

The correct order of $2$nd ionisation energy for the elements carbon, nitrogen, oxygen and fluroine is:

• A. $F>O>N>C$
• B. $C>N>O>F$
• C. $O>F>N>C$
• D. $O>N>F>C$

Answer 1

The correct option is C $O>F>N>C$

The second ionisation energy means the energy required to remove the electron from the corresponding monovalent cation of the respective atom. For $I{E}_2$, electronic configuration of $C^{+},N^{+},O^{+}$ and $F^{+}$-ions which are as follows.
$C^{+}=2s^2,2p1$
$N^{+}=2s^2,2p^2$
$O^{+}=2s^2,2p^3$
$F^{+}=2s^2,2p^4$.
$\because$ $O^{+}$ is half-filed configuration, obviously it is most stable and greater ionisation energy than $F^{+}$ as well as $N^{+}$.
The ionisation energy of an element depends upon its size as. Hence, correct order will be, $O>F>N>C.$