Define the following terms:

(a) Atoms

(b) Molecules

(c) Radicals

(d) Valency

(e) Periodic table

(a) An atom is the smallest particle of an element that exhibits all the properties of that element. It may or may not exist independently but takes part in every chemical reactions.

(b) A molecule is the smallest particle of an element or compound, made up of two or more atoms of an element or compound which has independent existence exhibiting all of their properties.

(c) A radical is an atom of an element or a group of atoms of different elements that behaves as a single unit with a positive or negative charge on it.

(d) Valency is the combining capacity of an element or of a radical.

(e) Periodic table is a tabular arrangement of elements in vertical columns and horizontal rows indicating the regular trends in the properties of elements.