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

Ion Valency	Ion Valency
(Charge)	(Charge)
Sodium 1+	Nitrate 1-
ion	Ion
Copper 2+	Sulphide 2-
ion	ion

Using this information, write down the formulae of:

(i) Sodium sulphide

(ii) Copper nitrate

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

Using this information, write down the formulate of the following compounds:

(i) Sodium phosphate

(ii) Ammonium sulphate

(iii) Calcium hydroxide

(iv) Lead bromide

What is the difference between a cation and an anion? Explain with examples.

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?

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