(i) Write the electron-dot structures for sodium, oxygen and magnesium. (ii) Show the formation of ${\mathrm{Na}}_2\mathrm{O}$ and $\mathrm{MgO}$ by the transfer of electrons. (iii) What are the ions present in these compounds?

Electron dot structures or Lewis dot formula can be drawn if the molecular formula of the compound is known. It defines the nature of bond and position of atoms of the molecule which are connected in the molecule. (i) The electron-dot structures for sodium and oxygen (ii) Formation of ${\mathrm{Na}}_2\mathrm{O}$ and $\mathrm{MgO}$ by the transfer of electrons Formation of Magnesium oxide: When magnesium reacts with oxygen, the magnesium atom transfers its two outermost electrons to an oxygen atom. By losing two electrons, the magnesium atoms form a magnesium ion $\left({\mathrm{Mg}}^{2+}\right)$ and by gaining two electrons, the oxygen atom forms an oxide ion $\left(0^{2-}\right)$. Formation of Sodium oxide: Two sodium atoms transfer their 2 outermost electrons to an oxygen atom. By losing two electrons, the two sodium atoms form sodium ions $\left(2{\mathrm{Na}}^{+}\right)$. And by gaining two electrons, the oxygen atom forms an oxide ion $\left({\mathrm{O}}^{2-}\right)$. (iii) The ions present in sodium oxide compound $\left({\mathrm{Na}}_2\mathrm{O}\right)$ are sodium ions ( $2{\mathrm{Na}}^{+})$and oxide ions $\left({\mathrm{O}}^{2-}\right)$. The ions present in the Magnesium oxide compound $(\mathrm{MgO})$ are magnesium ions ${\mathrm{Mg}}^{2+}$ and oxide ions $\left({\mathrm{O}}^{2-}\right)$.