Li⁺ ion being small in size can easily stablize small nitride ion N^3-,however other alkali metal ions because of their larger size cannot stablise smaller nitride ion.Thus,only lithium forms nitride.

Barium-grassy green

Potasium carbonate is soluble in water and does not precipitates when carbon dioxide is passed. Therefore solvay process is not used for the preperetion of potassium carbonate.

This is because, after removing two electrons from Mg, it acquire stable noble gas configuration or in other words, the higher enthalpy of lattice formation of Mg²⁺ is more than compensates the second ionisation enthalpy requires for the formation of divalent Mg²⁺ ions.

Due to small size and high ionisation enthalpy of Be, BeO is amphoteric in nature, i.e. it reacts with both acids and bases. Further due to small size, the hydration enthalpy of Be²⁺ ions is much higher than the lattice enthalpy of BeSO₄.As a result, BeSO₄ is highly soluble in water.

Since BeH₂ and BeCl₂ have only four electrons in the valence shell, therefore, they are electron deficient molecules.
To make up their electron deficiency, each Be atom forms four, three - center two-electron bonds or banana bonds. Thus, it is due to electron deficiency that BeH₂ and BeCl₂ have polymeric structures.

MgSO₄ . 7 H₂O;
\(Mg{ SO }_{ 4 }.7{ H }_{ 2 }O\xrightarrow [ 423K ]{ -6{ H }_{ 2 }o } Mg{ SO }_{ 4 }.{ H }_{ 2 }O\)
\(\\ \xrightarrow [ 573k ]{ -{ H }_{ 2 }O } Mg{ SO }_{ 4 }\xrightarrow [ Heat ]{ . } MgO+S{ O }_{ 3 }\)

When a satured solution of magnesium chloride is mixed with magnesium oxide, it sets to  a hard mass. This hard mass is known as magnesia cement . Its composition is MgCI₂ . 5 MgO . H₂O.