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

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There is an increase in nuclear charge of alkali metals

There is an increase in the nuclear charge of the alkaline earth metals

There is no change in the nuclear charge

There is decrease in the nuclear charge of the alkaline earth metals

answer is A.

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Detailed Solution

Alkali metals belong to the IA group having electronic configuration ${ns}^{1}$ i.e, half-filled and unstable. Whereas, alkaline earth metals belong to IIA group having electronic configuration ${ns}^{2}$ which is fulfilled and so, is stable.

The ns¹will readily try to lose its electron to attain the stable electronic configuration. And in alkaline earth metals ( ${ns}^{2}$ ), the atomic radii decrease and the nuclear charge increases as it has a stable electronic configuration. Hence, the reason for higher first ionization energy of alkaline earth metals due to an increase in the nuclear charge.

Therefore, option (A) is correct.

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