The number of atoms of the same type which combine to form a molecule of an element is called its :

1. Atomicity
2. Valency
3. Molecular formula
4. Compound

The atomicity of phosphorus is :

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

What does 2H represent ?

1. two atoms of hydrogen
2. two molecules of hydrogen
3. one molecule of hydrogen
4. none of the above

The symbol for calcium ion is :

1. Ca
2. Ca⁺
3. Ca²⁺
4. Mg²⁺