Editing Alkaline earth metal (section)

==Compounds of alkaline earth metals==

'''''Oxides'''''

The alkaline earth metal oxides are formed from the thermal decomposition of the corresponding [[carbonates]].
:CaCO<sub>3</sub> → CaO + CO<sub>2</sub> (at approx. 900°C)
In laboratory, they are obtained from hydroxides:
:Mg(OH)<sub>2</sub> → MgO + H<sub>2</sub>O
or nitrates:
:Ca(NO<sub>3</sub>)<sub>2</sub> → CaO + 2NO<sub>2</sub> + 1/2O<sub>2</sub>
The oxides exhibit basic character: they turn [[phenolphthalein]] red and [[litmus]], blue. They react with water to form hydroxides in an exothermic reaction.
:CaO + H<sub>2</sub>O → Ca(OH)<sub>2</sub> + Q
Calcium oxide reacts with carbon to form acetylide.
:CaO + 3C → CaC<sub>2</sub> + CO (at 2500°C)
:CaC<sub>2</sub> + N<sub>2</sub> → CaCN<sub>2</sub> + C
:CaCN<sub>2</sub> + H<sub>2</sub>SO<sub>4</sub> → CaSO<sub>4</sub> + H<sub>2</sub>N—CN
:H<sub>2</sub>N—CN + H<sub>2</sub>O → (H<sub>2</sub>N)<sub>2</sub>CO ([[urea]])
:CaCN<sub>2</sub> + 2H<sub>2</sub>O → CaCO<sub>3</sub> + NH<sub>3</sub>

'''''Hydroxides'''''

They are generated from the corresponding oxides on reaction with water. They exhibit basic character: they turn [[phenolphthalein]] pink and [[litmus]], blue. Beryllium hydroxide is an exception as it exhibits [[Amphoterism|amphoteric]] character.
:Be(OH)<sub>2</sub> + 2HCl → BeCl<sub>2</sub> + 2 H<sub>2</sub>O
:Be(OH)<sub>2</sub> + NaOH → Na[Be(OH)<sub>3</sub>]

'''''Salts'''''

Ca and Mg are found in nature in many compounds such as [[Dolomite (mineral)|dolomite]], [[aragonite]], [[magnesite]] (carbonate rocks). Calcium and magnesium ions are found in [[hard water]]. Hard water represents a multifold issue. It is of great interest to remove these ions, thus softening the water. This procedure can be done using reagents such as [[calcium hydroxide]], [[sodium carbonate]] or [[sodium phosphate]]. A more common method is to use ion-exchange [[aluminosilicate]]s or [[ion-exchange resins]] that trap Ca<sup>2+</sup> and Mg<sup>2+</sup> and liberate Na<sup>+</sup> instead:
:Na<sub>2</sub>O·Al<sub>2</sub>O<sub>3</sub>·6SiO<sub>2</sub> + Ca<sup>2+</sup> → CaO·Al<sub>2</sub>O<sub>3</sub>·6SiO<sub>2</sub> + 2Na<sup>+</sup>