The valency of iron in Fe₂O₃ is:

1. 1
2. 2
3. 3
4. 6

Which of the following has valency 4?

1. Aluminium
2. Oxygen
3. Carbon
4. Phosphorus

The sulphate radical is written as SO₄^2-. What is the formula of calcium sulphate?

1. Ca(SO₄)₂
2. Ca₂(SO₄)
3. Ca(SO₄)₃
4. CaSO₄

State the term for the following:

(a) The number of atoms present in a molecule of an element.

(b) The symbolic representation of a molecule.

(c) A group of atoms that react as a single unit.

(d) The combining capacity of an element.

(e) The tabular arrangement of elements in horizontal rows and vertical columns.