Question

Which element of the following has the smallest first ionization energy?

• A. $Li$
• B. $Mg$
• C. $K$
• D. $Be$

Answer 1

The correct option is C $K$

The ionization energy decreases down the group and increases along the period towards right. Thus the comparisons are $Li>K,Li<Be,Be>Mg,Mg>K$.

Thus the least value is of $K$. Hence answer is option C.