Question

The first ionisation potential of $N,P,O$ and $S$ are in the order of:

• A. $S>P<O>N$
• B. $N>O>P>S$
• C. $N>O<P>S$
• D. $N<O<P<S$

Answer 1

The correct option is B $N>O>P>S$

Moving left to right within a period or upward within a group, the first ionization energy generally increases with a few discrepancies (aluminum and nitrogen group).

Nitrogen group to oxygen group, I.P. decreases instead of increasing because of the stable half-filled configuration of nitrogen family.

$N\left(1400\right)>O\left(1313\right)>P\left(1011\right)>S\left(999\right)$