Amongst the elements with following electronic configurations, which one of them may have the highest ionisation energy ?
- [Ne] 3s2 3p2
- [Ar] 3d10 4s2 4p3
- [Ne] 3s2 3p1
- [Ne] 3s2 3p3
Answer
(4) [Ne] 3s2 3p3
Solution
(1) [Ne] 3s2 3p2 = Si, (2) [Ar] 3d10 4s2 4p3 = As, (3) [Ne] 3s2 3p1 = Al, (4) [Ne] 3s2 3p3 = P
∵ Ionisation enthalpy increases across a period, Al < Si < P; P also has a stable half-filled 3p3 subshell.
∵ Ionisation enthalpy decreases down a group, As (period 4) < P (period 3).
∴ P, [Ne] 3s2 3p3, has the highest ionisation energy.
Answer: (4)