Which of the following species has the highest ionisation potential?

Which of the following presents the correct order of second ionization enthalpies of $C$,$N$,$O$ and $F$?

In the $2^{nd}$ period,which element has the highest value of the sum of the $1^{st}$ and $2^{nd}$ ionization energy $(I.E.)$?

The second ionization potential is

Why does the successive ionization enthalpy of an element increase in the order: $1^{st} < 2^{nd} < 3^{rd}$?

The given electronic configurations are for elements $X$,$Y$,and $Z$. Note that these configurations represent ions of the elements:
$X = [Ne] \, 3s^2 \, 3p^5$
$Y = [Ne] \, 3s^2 \, 3p^6$
$Z = [Ne] \, 3s^2 \, 3p^4$
Determine the correct statement regarding the energy changes associated with these configurations.