Write down the formulae of
(i) sodium oxide
(ii) aluminium chloride
(iii) sodium sulphide
(iv) magnesium hydroxide
To find the formula of an ionic compound, first, identify the cation and write down its symbol and charge. Then, identify the anion and write down its symbol and charge. Finally, combine the two ions to form an electrically neutral compound.
For Example :
(i) Sodium oxide →Na2O
(ii) Aluminium chloride → AlCl3
(iii) Sodium sulphide → Na2S
(iv) Magnesium hydroxide → Mg(OH)2