Question

The correct order of ionization energy for comparing carbon, nitrogen and oxygen atoms is

• A. C > N > O
• B. C > N < O
• C. C < N > O
• D. C < N < O

Answer 1

The correct option is C

C < N > O

$\to$ Generally as atomic radius decreases ionization energy increases.

Good

Now, we know that along a period from left to right atomic radius decreases.

Therefore,

IE, order should be

C < N < O

But, because N has half filled orbitals, it is taken as more stable configuration and it will not lose electron so easily.

That's why we have to apply more energy in case of nitrogen.

In a period, the ionization energy of VA elements is more than the elements of VIA because the half filled $p^3$ configuration of VA elements is comparatively of higher stability. VIA group elements ($p^4$) configuration by the loss of one electron. Ionization energy

N(1$s^2$ 2 $s^2$ 2 $p^1$ x${p_y}^1$ ${p_z}^1$) >0

1$s^2$ 2 $s^2$ 2 $p^2$ x${p_y}^1$ ${p_z}^1$

Thus P > S; As(947) > Se(941)
Therefore, it will be
C < N > O