The correct order in which the first ionzation enthalpy increases is

Options

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

Answer

C

Explanation

In general, the ionization enthalpy increases across the period on account of increase of `Z_(eff)` but decreases down the group on account of increase of atomic size.

Thus, the correct order is
`Be(899) gt Na (496) lt K (419)`
The very high ionization enthalpy of `Be` is due to its very small size and also due to its stable configuration `(1s^(2)2s^(2))`.