1. Chapter 4: Atomic Structure
Section 1: Studying Atoms

2. Ancient Greek Models of Atoms
The Greek philosopher Democritus was the first person to put forth a theory that matter was made of tiny particles.
He called these particles “atomos”, which is Greek for “uncut”

3. Ancient Greek Models of Atoms
Another Greek philosopher, Aristotle, believed everything was made of only four elements: air, fire, earth, and water.

4. Dalton’s Atomic Theory
John Dalton, a British teacher, developed his atomic theory around 1810.
He was the first person to perform experiments and have evidence about atoms.

5. Dalton’s Atomic Theory
Dalton’s Theory:
All matter is made of atoms
Atoms of the same element weigh the same
Compounds are made of more than one type of atom
To form compounds, the same types of atoms join together in specific amounts

6. Thomson’s Model of the Atom
J.J. Thomson, a British professor, used a cathode ray tube in an experiment around 1897.
This experiment showed that atoms were not solid spheres, but were made of smaller particles.

7. Thomson’s Model of the Atom
Thomson’s model was called the “plum pudding” model.
He believed that negative electrons were scattered around inside the positive atom like plums inside a pudding.

8. Rutherford’s Atomic Theory
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9. Rutherford’s Atomic Theory
Based on the results of his gold foil experiments, Rutherford proposed that atoms had a nucleus.
The nucleus is a dense center where all the positive charge in an atom is located.