Which of the following electronic configuration corresponds to an element with the lowest ionization energy ?

Options

A. `1s^(2)2s^(2)2p^(3)`
B. `1s^(2)2s^(2)2p^(5)`
C. `Is^(2)s^(2)2p^(6)`
D. `Is^(2)2s^(2)2p^(6)3s^(1)`

Answer

D

Explanation

Alkali metals have low ionisation energies. Outer electronic configurations of alkali metals are `(n-1)s^(2)p^(6),ns^(1)`.