Question

The set representing the correct order of first ionisation potential is :

• A. $K>Na>Li$
• B. $Be>Mg>Ca$
• C. $B>C>N$
• D. $Ge>Si>C$

Answer 1

The correct option is B $Be>Mg>Ca$

Size increases as we move down the group. Therefore, the outer electrons experience less attraction due to increase in distance, i.e., the effective nuclear charge experienced is less. Less the effective nuclear charge less the I.P. Therefore, I.P of $Be>Mg>Ca$.