Question

Which element has a third ionization energy which is significantly greater than its first or second ionization energies?

• A. $Br$
• B. $As$
• C. $Ga$
• D. $Ca$

Answer 1

The correct option is D $Ca$

On removal of $2$ electrons from $Ca$, it attains configuration of $Ar$ which is an inert gas and its configuration is extremely stable. Hence excessive energy is needed to break this configuration. Thus the third IE of $Ca$ is significantly higher than that of its second or first. No such factor is observed in the elements mentioned in other options.