Molecules can be classified based on the number of atoms they contain (monoatomic, diatomic, triatomic, polyatomic), the type of atoms (homoatomic containing the same type vs heteratomic containing different types), and their size (micro molecules are small while macromolecules are large, containing thousands of atoms). Common examples of different types of molecules include diatomic molecules like O2 and N2, heteratomic triatomic molecules like H2O and CO2, and macromolecules like proteins.

1. Molecules
The smallest part of pure
substance which can exist
independently.
For Example: He, N2, O2 etc
In a molecule there may be one
or more than one atoms

3. Classification of Molecules
 Molecule may be classified on
the basis of:
1. Number of Atoms present in
molecule
2. Type of Atoms present in
molecule
3. Size of Atom present in
molecule

4. 1. Number of Atoms.
Mono atomic
• The molecules which consist of
only one atom are called Mono
atomic Molecules
• For example: He, Ne, Ar , etc.
• Note: Only Noble gasses are
Monoatomic molecules in
UNIVERSE.

5. Di-atomic Molecules
The molecules which are consist
of two atoms are called di-
atomic molecules
For example: H2 ,O2 , N2, Cl2 etc.
Molecules are formed for the
sake of Compeletion duplets
and octets of the atoms.

6. Tri-atomic Molecules
• The molecules which are consist
of three atoms are called tri-
atomic molecules.
• For example: CO2, O3, H2O etc.

7. Polyatomic Molecules
• The molecules which are consist
of many atoms are called
Polyatomic molecules
• For example: C6H12O6, H2SO4

8. Type of Atoms
On the Basis of type of atoms
molecules may be have two
types
1. Homo-atomic
2. Hetro-atomic

9. Homo & Hetro Atomic Molecules
The molecules which are consist
of same type of atoms are called
homoatomic molecules
For Example H2, N2, Cl2 etc.
The molecules which are consist
of different type of atoms are
called hetroatomic molecules
For example: H2O, CO2, etc.

10. Micro and Macro Molecules
On the basis of Size molecule
may have two types
1. Micro molecules
2. Macromolecules

11. Micro Molecules
The molecules which are small in
size and have low molecular weight
are called micro molecules.
For example CO2, CH4, etc.
All the molecules which we consider
in chemistry are almost
micromolecules almost

12. Macro Molecules
The molecules which are larger
in size and have high molecular
weights are called
macromolecules.
For Example. haemoglobin,
Steroids, Carbohydrates, etc.
There are 10 thousand atoms in
haemoglobin and it is 68
thousand times heavier than
Hydrogen atom

13. Atomicity

16. Questions.
What are molecules? Give examples
Differentiate between micro and macro molecules
What are homo and hetro molecules? Give examples.
What are Mono di and tri atomic molecules? give examples of each.