State three reasons for the following fact: $(a)$ Magnesium is a metal. One of the reasons must be supported with a chemical equation.

(N/A) Magnesium $(Mg)$ is considered a metal due to the following reasons:
$1.$ Magnesium is a hard solid with a high melting and boiling point,which are characteristic physical properties of metals.
$2.$ Magnesium atoms lose two electrons to form electropositive $(Mg^{2+})$ ions and act as good conductors of heat and electricity.
$3.$ Magnesium reacts with oxygen to form a basic oxide,which dissolves in water to form a base. This is a characteristic chemical property of metals.
Chemical equations:
$(a) 2Mg(s) + O_2(g) \rightarrow 2MgO(s)$
$(b) MgO(s) + H_2O(l) \rightarrow Mg(OH)_2(aq)$
Since magnesium exhibits these metallic properties,it is classified as a metal.