Published by:
CGP EDU Academic Team
Published on: August 12, 2026
Arrange the elements 
and S in the order of increasing first ionisation enthalpy.
A
P 
S 
O 
N
S O N
B
S 
P 
O 
N
P O N C
D
P 
S 
N 
O
S N O
Text Solution
Verified by ExpertsThe correct answer is:
B
Period | Group 15 | Group 16 |
2nd period | N | O |
3rd period | P | S |
Ionisation enthalpy of nitrogen ( 
is greater than oxygen 
due to presence of extra stable exactly half-filled 
-orbitals.
Similarly, ionisation enthalpy of phosphorus 
) is greater than sulphur ( 
). On moving down the group, ionisation enthalpy decreases with increasing atomic size. So, the increasing order is 
First ionisation enthalpy increases.
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