Question

Second ionization energy of alkali metals is very high whereas that of alkaline earth metals is low

Answer 1

After losing 1 electron, the alkali metals obtain noble gas configuration and become highly stable. And alkali earth metals obtain alkali metals' configuration.
Hence the second ip of alkali metals becomes very high due to its stabilty.
And the second ip of alkali earth metal is low as they can easily lose 1 electron to gain noble gas configuration.

Answer 2

Answer:

second ionization energy of alkali metals is very high because by loosing one electron they achieve inert gas configuration