Atoms and Molecules

The postulates of modern atomic theory are as follows-

1. All matter is made up of atoms.

2. Atom can be divided further into subatomic particles like electrons, protons and neutrons.

3. Atoms of same elements may not be identical in all respect.

Example: Isotopes (₁H¹, ₁H², ₁H³)

4. Atoms of different elements may be identical in some respect.

Example: Isobars (₁₈Ar⁴⁰, ₂₀Ca⁴⁰)

5. Atom is the smallest particle which participates in a chemical reaction.

6. The ratio of atoms in a molecule may be fixed and integral but it may not be simple.

For example, C₁₂H₂₂O₁₁, here the ratio of C, H and O atoms (12:22:11) is not simple.

7. Atoms of on…