Which atoms do alkaline-earth metal ions preferentially bind to in compounds?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — alkaline-earth metal Modern version of the periodic table of the elements (printable).

Alkaline-earth metals are considered to form "hard" ions, which means they preferentially bind to ligands containing hard donor atoms such as oxygen, nitrogen, or fluorine.1

These metals typically form doubly charged $M^{2 +}$ ions in their compounds, which are stabilized through electrostatic interactions with these hard donor atoms or within ionic lattices. Because of their electropositive character, the strength of the bonding and the coordination behavior of these ions are heavily influenced by the size of the ion and the nature of the ligand. For instance, these ions are readily hydrated, with the metal ion coordinating to the oxygen atom of water molecules.123