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How do calcium, strontium, and barium behave when dissolved in liquid ammonia?

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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).

When calcium, strontium, and barium are dissolved in liquid ammonia, they form dark blue solutions. These solutions are of significant scientific interest because they are believed to contain metal ions and solvated electrons, which result from the interaction between the metal and the solvent.1

The behavior of these metals in ammonia is characterized by the following:

Appearance: At low concentrations, the solutions are dark blue. As the concentration of the dissolved metal increases, the color deepens and eventually transitions to a copper-colored solution that exhibits a metallic lustre.12
Chemical Properties: These solutions act as strong reducing agents and are useful in various chemical processes.1
Formation of Ammoniates: If the solvent is evaporated, the resulting residues contain ammonia in the form of ammoniates, which generally follow the formula $M (N H_{3})_{6}$ .1
Decomposition: Over time, these ammoniates decompose to form amides with the general formula $M (N H_{2})_{2}$ .1