The correct order in which the first ionization potential increases is

Options

A. K , Be , Na
B. Be, Na K
C. Na , K, Be
D. K, Na, Be

Answer

D

Explanation

The electronic configuration of the elements are
`._(4)Be-1s^(2)2s^(2)`
`._(11)Na-1s^(2)2s^(2)2p^(6)3s^(1)`
`._(19)K-1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(1)`
The first ionization energy of Be is maximum because electron is to be drawn from stable (fully filled) orbital. The `1^(st)` ionization energy of Na is greater than K because size of the K is bigger than Na which facilitates easy removal of electron from its outermost shell.
So, the sequence is `KltNaltBe`.