Q. Correct order of first ionisation potential among the following elements Be, B, C, N, O is
A) $B < Be < C < O < N$
B) $B < Be < C < N < O$
C) $Be < B < C < N < O$
D) $Be < B < C < O < N$
Explanation
(a)
The ionisation potential increases from left to right in a period but the first ionisation potential of nitrogen is greater than oxygen due to half-filled stable configuration and ionisation potential of Be is greater than B due to completely filled $s$-orbital. Hence, the order of ionisation potential is as
Element : B < Be < C < O < N
IP (eV) : 8.3 9.3 11.2 13.6 14.5
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.