The ion that would represent the most common ion of an element from group 2A is A 2+
explanation
Group 2A are group of elements in periodic table which are known as alkaline earth metals.
Example of group 2A elements is magnesium and calcium.
Group 2A has 2 valence electron in their outer most shell and therefore they form ion which is positively charged by loses the 2 valence electrons.
for example magnesium (Mg) which has 2.8.2 or [Ne] 3S2 electron configuration loses the 2 valence electron to form Mg2+ ion. Therefore A2+ ion represent the common ion of group 2A element.
