Elements X, Y and Z have atomic numbers 6, 9 and 12 respectively. Which of them will form a cation :

1. Z
2. Y
3. X
4. Depends on the reactivity of the elements.

The atomic numbers of elements A, B, C and D are 2, 6, 12 and 20 respectively. Which of them has 2 electrons in its N shell?

1. A
2. D
3. B
4. C

The acidic radical in Sulphurous acid is:

1. H⁺
2. SO₃^-1
3. SO₄^-3
4. SO₃^-2

When an oxygen ion is converted to an oxygen atom, it undergoes:

1. Reduction
2. Redox reaction
3. Oxidation
4. Combination reaction