Question

The order of first ionisation energies of the elements Li, Be, B, Na is

• A. Li > Be > B > Na
• B. Be > B > Li > Na
• C. Na > Li > B > Be
• D. Be > Li > B > Na

Answer 1

Answer: (B)

Be > B > Li > Na

Answer 2

$Na : 1s^22s^22p^63s^1 ; Li: Is^22s^2$ $Be : 1s^2 2s^2 ; B : Is^2 2s^2 2p^1$ Thus correct order of I.E, is as follows Be > B > Li > Na $IE_1$ of Be is more than B. It is due to its extra stable electronic configuration with fully filled 2s-subshell