Which one of the following is correct order of second ionisation potential of Na, Ne, Mg and AI?

Options

A. `Al lt Na lt Mg lt Ne`
B. `Ne lt ALlt Na lt Mg`
C. `Mg lt AL lt Ne lt Na`
D. `Na lt Mg lt Ne lt AI`

Answer

C

Explanation

Valence electronic configuration of given elements after first ionisation is
` Na^(+) : 2s^(2) 2p^(6)`
`Ne^(+) : 2s^(2) 2p^(5)`
`Mg^(+) : 3s^(-)`
` Al^(1) : 3^(2)`
Generally, the ionisation energy increases and the size of the atom/ion decreases from left to right in a period. First ionisation potential is greater than the second ionisation potential. Since, Nat reaches stable electronic configuration by losing one electron, its second ionisation energy is greatest among the given ions.
The order of their `IE_(2)` is Mg