Define the following terms:

(a) Atoms

(b) Molecules

(c) Radicals

(d) Valency

(e) Periodic table

Write the names of the elements present in the following compounds.

(a) Common salt

(b) Ammonia

(c) Sulphuric acid

(d) Glucose

(e) Sodium hydroxide

(f) Acetic acid

Write the symbols and valencies of the following radicals:

(a) Magnesium ion

(b) Ammonium

(c) Carbonate

(d) Nitrate

(e) Oxide

(f) Bisulphate

(g) Aluminium ion

Name the following radicals:

(a) SO₄^2-

(b) HCO₃^-

(c) OH^-

(d) Cr₂O₇^2-