Why are the second ionisation energies of alkaline earth metals much smaller than those of alkali metals ?

The densities of alkaline earth metals are much smaller than those of alkali metals.

Assertion : The alkaline earth metal hydroxides are more basic than the corresponding alkali metal. Reason : The ionisation enthalpies of alkaline earth metals are much lower than those of alkali metals.

Alkaline earth metals show:-

The ionisation enthalpy of alkaline earth metals is

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

The outer electronic configuration of alkaline earth metals is

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

The correct order of hydration energy of alkaline earth metal ions is

(a). Which alkaline earth metals do not give characteristic colour to the Bunsen flame? (b). Why alkaline earth metals do not form tripositive ions? (c ). Why alkaline earth metals are diamagnetic, but alkali metals are paramagnetic? (d). Why the first inonisation enthaply pf alkaline earth matals is higher than those of corresponding alkali metals? (e). Why alkaline earth metals are less electropositive than corresponding alkali metals?

(a) Why alkaline earth metals are harder, have higer melting ponts and higher densities than the alkali metals? (b). Why the atoms of alkaline earth metals are smaller than the corresponding alkali metals? (c ). Why alkaline earth metals have high electrical and thermal conductivities? (d). What is black ash? (e). Why the variation in physical properties of alkaline earth elements is not as regular as in the case of alkali metals?