What are the bonding capabilities for the Alkaline Earth Metals?
This answer is in case you don't know what cations and anions are. Both have to do with when an atom (or molecule) gains or loses electrons, which means there are more or less electrons in the electron shell(s) than there are protons in the nucleus (nuclei).
cation = an atom or molecule with fewer electrons than protons, so it has a positive charge
anion = an atom or molecule with more electrons than protons, so it has a negative charge
So, the alkaline earth metals all easily lose 2 electrons, and turn into positive cations (fewer electrons than protons). Since they are short on electrons, they are inclined to bond with anions which have too many electrons.