An element is placed in $2^{nd}$ Group and $3^{rd}$ Period of the Periodic Table. It burns in the presence of oxygen to form a basic oxide.
$(a)$ Write a balanced chemical equation when this oxide is dissolved in water.
$(b)$ Draw the electron dot structure for the formation of this oxide.

(N/A) The element in the $2^{nd}$ Group and $3^{rd}$ Period is Magnesium $(Mg)$.
$(a)$ When magnesium oxide $(MgO)$ is dissolved in water,it forms magnesium hydroxide $(Mg(OH)_2)$:
$MgO(s) + H_2O(l) \rightarrow Mg(OH)_2(aq)$
$(b)$ The electron dot structure for the formation of magnesium oxide involves the transfer of $2$ electrons from the magnesium atom to the oxygen atom:
$Mg: + :\ddot{O}: \rightarrow [Mg]^{2+} [: \ddot{O} :]^{2-}$