Answer:
Molecules are the smallest particle of a compound or element which can be found in nature as a free entity and made up of atoms bonded together. The molecules can not take part in the chemical reaction on their own directly.
An atom is on other hand is the smallest particle that does not exist free in nature and bonded together to form molecules and involves in the chemical reactions directly.
Therefore we can say that the molecules are formed by atoms while the atom exists as an entity in nature.
