The symbol of sulphite ion is:

1. SO₄^2-
2. HSO₄^-
3. SO₃^2-
4. S^2-

Which of the following sets of elements show variable valencies?

1. Iron and calcium
2. Copper and sodium
3. Lead and mercury
4. Silver and potassium

The valencies shown by copper is:

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

Which of the following represents the correct symbol of potassium ion ?

1. K
2. K⁺
3. K²⁺
4. K³⁺