$(i)$ Write the electron-dot structures for sodium,oxygen,and magnesium.
$(ii)$ Show the formation of $Na_{2}O$ and $MgO$ by the transfer of electrons.
$(iii)$ What are the ions present in these compounds?

(N/A) $(i)$ The representation of elements with valence electrons as dots around the element symbol is referred to as the electron-dot structure.
$(a)$ Sodium $(2, 8, 1) = Na^{\bullet}$
$(b)$ Oxygen $(2, 6) = :\ddot{O}:$
$(c)$ Magnesium $(2, 8, 2) = Mg^{\bullet\bullet}$
$(ii)$ Formation of $Na_{2}O$:
$2Na^{\bullet} + :\ddot{O}: \rightarrow (Na^{+})_{2}[:\ddot{O}:]^{2-}$
Formation of $MgO$:
$Mg^{\bullet\bullet} + :\ddot{O}: \rightarrow (Mg^{2+})[:\ddot{O}:]^{2-}$
$(iii)$ The ions present in $Na_{2}O$ are $Na^{+}$ and $O^{2-}$ ions,and in $MgO$ are $Mg^{2+}$ and $O^{2-}$ ions.