Why do alkaline-earth metal salts usually form ionic compounds?

Alkaline-earth metal salts typically form ionic compounds because these metals possess two electrons in their outermost s orbitals, which are relatively easily removed to form stable, doubly charged $M^{2+}$ ions.1

The formation of these ionic structures is driven by the following factors:

• Electronic Stability: By losing their two valence electrons, the metal atoms achieve a stable electronic configuration corresponding to that of a noble gas.1
• Energy Compensation: Although removing the second electron requires more energy than the first, this expenditure is more than compensated for by the significant binding energy released when the resulting $M^{2+}$ ion interacts with anions in an ionic lattice or is stabilized by a solvent.1
• Electrostatic Attraction: In an ionic solid, the positively charged metal cations are surrounded by negatively charged anions. The strong electrostatic attraction between these oppositely charged ions creates a stable ionic bond, which is the preferred bonding state for most of these elements.12

While this ionic model is highly accurate for heavier members of the group, it is less applicable to beryllium and magnesium, as their smaller ionic radii and high charge-to-size ratios can lead to more covalently bonded structures.3