How do alkaline-earth metal ions interact with water molecules?

Alkaline-earth metals form doubly charged $M^{2+}$ ions that are readily hydrated when in contact with water. This interaction is driven by the electrostatic stabilization of the metal ion by water molecules, which act as ligands due to their high dielectric constant.12

The number of water molecules that coordinate directly to the metal ion depends on the size of the ion, with larger ions accommodating more water molecules for steric reasons. Typically, the coordination numbers are 4 for $B{e}^{2+}$, 6 for $M{g}^{2+}$, and 6–8 for $C{a}^{2+}$. While these ions readily bind to water, the strength of the bonding to the water molecules decreases as the ionic radius increases.1

These hydrated ions are essential to the chemistry of the group, as the energy required to remove the metal's two valence electrons is compensated for by the binding energy provided by the solvent or by the formation of an ionic lattice.2