The set representing the correct order for the first ionisation potential is

Options

(a) K > Na > Li
(b) Be > Mg > Ca
(c) B > C > N
(d) Ge > Si > C

Correct Answer:

Be > Mg > Ca

Explanation:

The ionisation potential decreases in a group on moving downward because atomic radius increases hence, the correct order is Be>Mg>Ca