It is very easy to obtain `M^(+)` ion from an atom of alkaline earth metals. But `M^(+)` ions are not formed. Why? 

Explanation

Though the formation of `M^(+2)` ions is difficult ,alkaline earth metals are familier to have them in solid state as well as in solution state .
the lattice energy in sold state or hydration energy in solutions of `M^(2+)` ions is more . this dominates the second ionisation energy of alkaline earth metals .