1. Chapter 4: Atoms

2. Section 1: The Development of Atomic Theory

3. Timeline of Atomic Models

4. The Beginnings of Atomic Theory
In the fourth century BCE, the Greek philosopher Democritus suggested that the universe was made by indivisible units

5. Dalton’s Atomic Theory
According to Dalton, all atoms of a given element were exactly alike, and atoms of different elements could join to form compounds

6. Thomson’s Model of the Atom
Thomson’s cathode-ray tube experiment suggested that cathode rays were made negatively charged particles that came from inside atoms
Electron is a subatomic particle that has a negative charge

7. Rutherford’s Model of the Atom
Rutherford proposed that most of the mass of the atom was concentrated at the atom’s center
The nucleus is an atom’s central region, which is made up of protons and neutrons