How is an ion different from an atom? How is cation different from anion?

Write the atomicity of the following:

(i) I₂ (ii) H₂S

(iii) HNO₃ (iv) Na₂SO₄

(v) S₈

An oxide of nitrogen is found to contain nitrogen and oxygen combined together in the ratio of 7: 16 by mass. Derive the formula of the oxide and name it.

Predict the total number of atoms in each case.

(i) Calcium phosphate

(ii) Hydrogen sulphide

(iii) Magnesium bromide

(iv) Sodium oxide

(v) Aluminium hydroxide

Give symbol and valency of the following ions.

Hydroxide ion, carbonate ion.