The first ionisation potential of aluminium is smaller than that of magnesium because

Options

A. Atomic size of `Al gt` Atomic size of Mg
B. Atomic size of `Al lt ` Atomic size of Mg
C. Al has one electron in p- orbital
D. None of these

Answer

C

Explanation

`Al (3s^(2)p^(1)) and Mg(3s^(2))`. Lower energy is required to remove `3p^(1)` electron than `3s^(1)` electron (penctrating effect is `s gt p gt d gt f`). Secondly Mg has stable electronic configuration than AI