Question

Which of the following order of ionisation energy is correct?

• A. $B < Be < N < C$
• B. $Be>B>C>N$
• C. $B < Be < C < N$
• D. $Be < B < C < N$

Answer 1

Answer: (C)

$B < Be < C < N$

Answer 2

Ionisation energy generally increase in a period from left to right. But due to comparatively stabler configuration of Be $\left(1 s^{2}, 2 s^{2}\right)$, it has more ionisation energy than Boron $\left(1 s^{2}, 2 s^{2} 2 p^{1}\right)$. Hence, the correct order is : $B < Be < C < N$