Write the symbols/formulae of two simple ions and two compound ions (or polyatomic ions).

The valencies (or charges) of some of the ions are given below:

Using this information, write down the formulae of:

(i) Sodium sulphide

(ii) Copper nitrate

Explain the formation of (i) sodium ion, and (ii) chloride ion, form their respective atoms giving the number of protons and number of electrons in each one of them. What is the reason for positive charge on a sodium ion and a negative charge on a chloride ion?

An element Y has a valency of 4. Write the formula for its:

(i) chloride

(ii) oxide

(iii) sulphate

(iv) carbonate

(v) nitrate

Define ‘formula unit’ of an ionic compound. What is the formula unit of (i) sodium chloride, and (ii) magnesium chloride?