Summary

Dalton's Atomic Theory

Basis of Theory:
- Based on evidence and observation.
Key Postulates:
- Indivisibility: Atoms are indivisible, meaning they cannot be broken down into smaller particles by chemical means.
- Elemental Composition: Each element consists of only one type of atom, and the atoms of each element are unique.
- Compounds: Compounds are made up of atoms from two or more elements that are combined in fixed proportions.
- Rearrangement in Reactions: During chemical reactions, atoms rearrange themselves to form new substances.

J.J. Thomson:
- Discovered the existence of smaller particles within atoms, known as electrons.
- Proposed the Plum Pudding Model, which suggested that atoms are composed of electrons scattered throughout a positively charged medium, like plums in a pudding.
Robert Milliken:
- Conducted experiments that led to the determination of the charge of an electron, refining the understanding of atomic structure.
Ernest Rutherford:
- Conducted experiments that disproved the Plum Pudding Model, demonstrating that the majority of an atom's mass is concentrated in the nucleus.
- Revealed that most of an atom is actually empty space, leading to the modern understanding of atomic structure.