The first ionisation energies of alkaline earth metal are higher than those of the alkali metals. This is because:

Options

A. there is increase in the nuclear charge of the alkaline earth metal
B. there is decrease in the nuclear charge of alkaline earth metal
C. there is no change in the nuclear charge
D. none of these

Answer

A

Explanation

Along the period from left to right, atomic number increaes and, therefore, nuclear charge also increases. So first ionization energies of alkaline earth metals are higher than those of the alkali metals of the same period because of higher nuclear charge.