What is the correct order of `2^(nd)` ionisation energy

Options

A. `C lt O lt N lt F`
B. `C lt N lt O lt I`
C. `C lt F lt N lt O`
D. `C lt N lt F lt O`

Answer

4

Explanation

`C^(+)-1s^(2)2s^(2)2p^(1)," "N^(+)-1s^(2)2s^(2)2p^(2)," "O^(+)-1s^(2)2s^(2)sp^(3)," "F^(+)-1s^(2)2s^(2)2p^(4)`
clearly `2^(nd) I.E.` has order `OgtFgtNgtC`.