The symbols of some of the ions are given below

Na+, Mg2+, H+, Cl, S2–


Using this information, find out the formulae of


(i) sodium carbonate


(ii) magnesium chloride


(iii) hydrogen sulphide

(i) Sodium carbonate


By applying criss-cross method:



Formula: Na2CO3


Thus, the formula for sodium carbonate is Na2CO3.


(ii) Magnesium chloride


By applying criss-cross method:



Formula: MgCl2


Thus, the formula for magnesium chloride is MgCl2.


(iii) Hydrogen sulphide


By applying criss-cross method:



Formula: H2S


Thus, the formula for hydrogen sulphide is H2S.


20