The ionisation energy of nitrogen is more than oxygen because of $:-$

What is the order of first,second,and third ionisation enthalpy? Why?

In the given graph,which point represents an alkali metal with the least atomic number?

Triad-$I$ $[N^{3-}, O^{2-}, Na^{+}]$
Triad-$II$ $[N^{+}, C^{+}, O^{+}]$
Choose the species of lowest $IP$ from triad-$I$ and highest $IP$ from triad-$II$ respectively.

The electronic configuration of elements $A, B$ and $C$ are $[He] 2s^1, [Ne] 3s^1$ and $[Ar] 4s^1$ respectively. Which one of the following orders is correct for the first ionization potentials (in $kJ \ mol^{-1}$) of $A, B$ and $C$?

The third ionization energy is maximum for