The document discusses molecules and their classification. It defines a molecule as the smallest particle of a pure substance that can exist independently. Molecules can be molecular elements like oxygen or molecular compounds like methane. Molecules exist independently because they are formed by the combination of unstable atoms that become stable. Molecules are classified based on atomicity, nature, and size. Atomicity refers to the number of atoms in a molecule. Nature describes if a molecule contains the same (homoatomic) or different (heteroatomic) atoms. Size can be micro-molecules that are simple and exist as monomers, or macro-molecules that are large polymers like hemoglobin, starch, and cellulose. Hemoglobin in particular is

2. Prof. Sohaib Hasnain
Punjab Group of Colleges, Faisalabad
CHEMISTRY

4. WHAT IS MOLECULE

5. A molecule is the smallest particle of a pure
substance which can exist independently.

6. WHAT IS PURE SUBSTANCE ?
Element
Atomic Elements
Na, Li, Ca, K, Fe
 Molecular Elements
O2, Cl2, O3
 Compound
Molecular Compound
H2SO4, CO2, C6H12O6, C6H6, CH4
Ionic Compounds
NaCl, NaBr, KCl, NaF

7. “Molecular Elements and
Molecular Compounds are
termed as Molecule because
these exist independently”

8. MOLECULAR ELEMENT
 Oxygen
MOLECULAR COMPOUND
 Methane

9. Why Molecule Exists Independently?
 Molecule is formed by the combination of atoms
Atom forms bond to get stability
Molecule is stable specie because it is formed by the combination of
atoms
Molecule exist independently, because it is formed by the unstable
atoms which are now stable

10. CLASSIFICATION OF MOLECULES
On the basis of following parameter:
 ATOMICITY
 NATURE
 SIZE

11. ATOMICITY
The number of atoms present is a molecule is called atomicity
Examples
SUBSTANCE MOLECULE ATOMICITY
Carbon Dioxide CO2 3
Sucrose C12H22O11 45
Methane CH4 5
Sulphuric Acid H2SO4 7
Water H2O 3
Ethyl Alcohol C2H5OH 9

12. TYPES OF MOLECULE ON THE BASIS OF
ATOMICITY
 Mono-atomic Molecule
The molecule which contain only atom.
Examples : Noble Gases ( He, Ne, Ar, Kr, Xe and Rn)
 Poly-atomic Molecule
The molecule which contain two or more, same or different kinds of atoms
Examples : CO, CO2, H2SO4, C12H22O11, C2H5OH, H2O, CH4

13. TYPES OF MOLECULE ON THE BASIS
OF NATURE
 Homo-atomic Molecule
The molecule which are made up of same or one kind of atoms.
Examples : He, Cl2, O3, P4, S8
 Hetero-atomic Molecule
The molecule which are made up of different kinds of atoms
Examples : HCl, NH3, H2SO4,C6H12O6
.

14. TYPES OF MOLECULE ON THE BASIS
OF SIZE
Micro-molecules
 They are small in size
 They are simple molecule
 They exist as monomer
Examples
CO2, H2O, CH4
Macro-molecules
 They are large in size
 They have large no. of atoms
 They are exist as polymer
Examples
Haemoglobin, Starch, Cellulose
Chlorophyll

15. HAEMOGLOBIN

16. What is Haemoglobin
 It is a blood protein
 It carries oxygen from lungs and transport to the all parts of body
 Each molecule of hemoglobin is made up of 10000 atoms
 It is made up of Carbon, Hydrogen, Nitrogen, Oxygen and Iron
 It is 68000 times heavier than the hydrogen atom

17. STRUCTURE OF HEMOGLOBIN