Question

First ionisation enthalpy of alkaline earth metal are higher than corresponding group 1 metal but second ionisation enthalpy of alkaline earth metal are smaller than those of corresponding alkali metal why

Answer 1

First ionisation enthalpy of alkaline earth metals (group II) are higher than those of alkali metals (group I). Because the group II elements have ns² configuration which is a stable one, So to remove the outer electron more energy is needed. Whereas group I elements have ns¹ electrons and is easily removed.
After the removal of first electron group I elements have stable octet configuration and from it the removal of one more electron is very tough and it needs lots of energy to remove that electron. Whereas group II elements have after the removal of 1 electron have ns^​1 configuration, so removal of second electron is easy.