Which element having the following electronic configuration has minimum ionisation potential?

Options

A. `1s^(1)`
B. `1s^(2),2s^(2)2p^(6)`
C. `1s^(2),2s^(2)2p^(6),3s^(1)`
D. `1s^(2),2s^(2)2p^(2)`

Answer

C

Explanation

`1s^(2)2s^(2)2p^(6)3s^(1)`. It belongs to IA group which has least ionisation potential and it decreases down the group.