The first ionisation enthalpies of the alkline earth metals are higher than that of alkali metals but second ionisation ethalpies are smaller, why?

Options

A. In alkli metals, second ionisation enthylpy involves removal of electron from noble gas electronic configuration while in alkaline earth metals, second electron is removed from `ns^(1)` configuration
B. Alkaline earth metals hae very high melting point as compared to alkali metals.
C. Electrons in s-orbital aremore closely packed in alkaline earth metals than alkali metals.
D. due to smalle size alkaline earth metals do not form divalent ions very easily

Answer

A

Explanation

Alkaline earth metals-
`underset(ns^(2))(M)-1e^(-) overset(IE_(1))to underset(ns^(2))(M^(+)) underset(-1e^(-))overset(IE_(2))to underset(("Noble gas configuration"))(M^(2+))`
alkali metals-
`underset(ns^(1))(M)-1e^(-) overset(IE_(1))to underset(("Noble gas configuration"))(M^(+)) overset(IE_(2))to M^(2+), IE_(2) gt gt IE_(1)`