You should have an idea of what an ion is from the background reading done using Internet site link 

1. Cations and anions

Remember that atoms are electrically neutral, if an atom gains or loses electrons then it becomes charged

a. If an atom loses electrons it becomes positively charged (Cation)

Example : Sodium atom has 11 electrons it loses 1 electron to form a Sodium ion which has 10 electrons.

b. If an atom gains electrons it becomes negatively charged (Anion)

Example: Chlorine atom has 17 electrons it gains 1 electron to become a Chloride ion which has 18 electrons. The number of protons (positive charges does not change).

Atom: 17- 17+ so no charge Ion: 18- 17+ so charge of 1-

The atom gains or loses electrons so that it has a full outer shell of electrons.

The anions and cations combine together to form an electrically neutral compound.

These compounds are called ionic compounds.

Aqueous solutions of ionic compounds conduct electricity, due to the presence of the ions.

2. Polyatomic ions

These are ions that are made up of 2 or more different atoms. (Positively charged – cation, negatively charged – anion)

Examples:

Useful site for revision/reinforcement

Internet site link
Go to Chemistry, then ions. The section on Bonding is also useful.

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