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How does hydration change from beryllium ions to calcium ions?

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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).

The alkaline-earth metals readily undergo hydration when in solution. As you move from beryllium ions ( $B e^{2 +}$ ) to calcium ions ( $C a^{2 +}$ ), the hydration process changes in two primary ways:

Coordination Number: The number of water molecules directly attached to the metal ion increases due to the larger size of the ions. Typically, $B e^{2 +}$ coordinates with 4 water molecules, $M g^{2 +}$ with 6, and $C a^{2 +}$ with 6–8 molecules.1
Bonding Strength: While the number of associated water molecules increases with ionic radius, the strength of the bonding between the metal ion and the water molecules decreases as the ionic radius increases.1

In summary, while larger ions like calcium can accommodate more water molecules in their coordination sphere for steric reasons, the electrostatic attraction between the ion and the water molecules is weaker compared to the smaller, more highly polarizing beryllium ion.1