Molecule: The smallest component of a substance (an element or a compound) that can exist independently or freely in nature is called a molecule. A molecule is mostly formed by the chemical combination of atoms. It is the smallest unit of a substance. It shows all the properties of the substance and can exist independently.
Types of Molecules:
Molecules are classified on different basis. Some of the important classification are as follows…….
A) Classification of molecules on the basis of number of atoms: On the basis of number of atoms, molecules are of following types.
1)Monoatomic molecule: A molecule consisting of only one atom is called monoatomic molecule. For example, the inert gases helium, neon and argon all exist independently in atomic form and they are called monoatomic molecules.
2)Diatomic molecule: A molecule consists of two atomsis called diatomic molecule. For example: hydrogen (H2), oxygen (O2), chlorine (Cl2) and hydrogen chloride (HCl).
3)Triatomic molecule: A molecule consisting of three atomsis called triatomic molecule. For example: H2O and CO2.
4) Polyatomic molecule: A molecule consisting of many atoms is called polyatomic molecule. For example: methane (CH4), sulphuric acid (H2SO4) and glucose (C6H12O6).
- B) Classification of molecules on the basis of nature(type) of atoms.
1) Homoatomic molecule: A Molecule containing same type of atoms, is called homoatomic molecule. For example: hydrogen (H2), ozone (O3), sulphur (S8) and phosphorus (P4).
Heteroatomic molecule: When a molecule consists of different kinds of atoms, it is called heteroatomic molecule. For example: CO2, H2O and NH3.