Fill in the blanks with the correct words from the brackets.

1. A molecule of an element is …………… [water/chlorine/ammonia].

2. A radical with one atom of sulphur and three atoms of oxygen is …………… [bisulphite/sulphate/sulphite].

3. An element with variable valency is …………… [sodium/copper/calcium]

4. The formula of aluminum sulphate is …………… [AlSO₄ / Al₂(SO₄)₃ / Al₃(SO₄)₂]

5. The element lithium in the Modern Periodic Table with valency 1⁺ belongs to the group …………… [2/1]

Select the correct answer from A, B, C, D and E for each statement given below-

A: Molecule B: Orbits C: Atom D: Valency E: Radical

1. The basic unit of matter not capable of independent existence.

2. The smallest particle of a substance – capable of independent existence and which retains the characteristics of the substance.

3. An elementary particle of matter – of a group of atoms of different elements behaving as a single unit with charge on the group.

4. Imaginary path around the nucleus of an atom in which electrons revolve.

5. The term for the combining capacity of an element or the number of hydrogen atoms with which it combines or replaces.

Match the radicals in List I with their correct names from List II.

Name the following

1. A molecule of a compound containing two oxygen atoms and one nitrogen atom.

2. The radical containing one nitrogen and four hydrogen atoms.

3. The compound formed when iron [Fe²⁺] combines with oxygen [O^2-].

4. The group of the Modern Periodic Table to which calcium [Ca²⁺] belongs.

5. A non-metal which forms a polyatomic molecule with more than three atoms.