Question

The ascending order of the first ionization potential of C, N, O and F is _______

• A. C, O, N, F
• B. C, N, O, F
• C. C, N, F,O
• D. C,O, F, N

Answer 1

The correct option is A C, O, N, F

$C-1s^{2}2s^{2}2p^2$
$N-1s^{2}2s^{2}2p^3$
$O-1s^{2}2s^{2}2p^4$
$F-1s^{2}2s^{2}2p^5$

Hence as we move from left to right in a period atomic size decreases.I.P increases in general because it will be difficult to remove electron from the outer most shell if size is comparatively less.

But in case of O and N; though size of N is more than O still I.P is more for Nitrogen because of half filled stable configuration.

In remaining it follows general trend.C, O, N, F.

Option A is correct.