Question

Among $Be,B,Mg$ and $Al$, the second ionisation potential is maximum for:

• A. $B$
• B. $Be$
• C. $Mg$
• D. $Al$

Answer 1

Answer: (A)

$B$

Among $Be,B,Mg$ and $Al$, the second ionisation potential is maximum for $B$.

The electronic configuration of $B$ is $1s^{2}2s^{2}2p^1$. It loses the first electron to get the electronic configuration $1s^{2}2s^2$.

The second electron is to be removed from $2s$ electron which is completely filled. This will break the stable electronic configuration of filled $2s$ orbital. This requires a large amount of energy.

Hence, the correct option is $A$.