Chemical Properties of Group – II elements

The electrode potential of Be (Be²⁺/Be = -1.97 V) is least negative amongst all the alkaline earth metals. This means that Be is much less electropositive than other alkaline earth metals and hence does not react with water or steam even at red heat.

The electrode potential of Mg (Mg⁺²/Mg = -2.37 V), although more negative than that of Be yet is still less negative than those of alkali metals and hence it does not react with cold water but reacts with boiling water or steam.

or,  Mg + 2H₂O → Mg (OH)₂ + H₂

Ca, Sr and Ba have more negative electrode potentials similar to those of the corresponding group I alkali metals and hence react with even with cold water, liberating H₂ and forming the corresponding metal hydroxides.

Reaction with air (Nitrogen and Oxygen)

Be metal is relatively unreactive in the massive form and hence does not react below 873K. However, powdered Be is more reactive and burns brilliantly on ignition to give a mixture of BeO & Be₃N₂.

magnesium is more electropositive than Be and hence burns with dazzling brilliance in air to form a mixture of MgO and magnesium nitride.

Ca, Sr and Ba being even more electropositive react with air readily to form a mixture of their respective oxides and nitrides.

The reactivity towards oxygen increases as we go down the group. Thus Ca, Ba and Sr are stored in paraffin but Be and Mg are not because they form protective oxide layer on their surface.

All the alkaline metals burn in dinitrogen to form ionic nitrides of the formula, M₃N₂. This is in contrast to alkali metals where only Li forms Li₃N.

Be₃N₂ being covalent is volatile while the nitrides of all other elements are crystalline solids.

All these nitrides decompose on heating and react with water liberating NH₃.