1. Questions to answer: 1) What were the ancient elements?
2) What scientist ‘discovered the atom’? How did he come up with this theory (you may need to do some internet research to answer this question.)
3) What are the 4 parts to Dalton’s Atomic Theory?
4) Which part of his theory was later proved wrong, and why?
5) What was JJ Thompson’s contribution to the atomic theory?
6) What was Ernest Rutherford’s contribution to the atomic theory?
7) Which model is more accurate, the plum pudding model, or the electron cloud model?

2. The Structure of the Atom and the Periodic Table
Chapters 4 and 5

3. Atomic Theories- Ancient
Ancient Civilizations identified 4 elements:
Fire
Water
Wind
Earth
The elements could be converted into each other through a cycle
end

4. Atomic Theories- Modern
John Dalton
Father of modern atomic theory
Studied the behavior of gases
In all samples of the same substance, the ratio of the elements was always the same
end

5. Atomic Theories- Modern
Dalton's Atomic Theory:
All elements are made of atoms
Atoms of the same element have the same mass
This was later proved wrong- Isotopes
Atoms of different elements have different masses
Atoms combine in whole number ratios
You can't have half of an atom
Dalton's Atoms
Dalton went back to Democritus' view.
All matter is made up of individual particles called atoms, which cannot be divided
Atoms are little spheres
Like marbles

6. Atomic Theories- Modern
J. J. Thomson
Performed cathode ray tube experiments
Discovered the electron
When a magnetic field was applied the beam went toward the positive plate
When electricity moves through a gas it produces a glowing beam (neon signs)
end

7. Atomic Theories- Modern
Thomson came up with a new model of the atom to explain his results:
The Plum Pudding Model
Large area of positive charge
Small packets of negative charge
Think: Chocolate Chip Cookies
end

8. Atomic Theories- Modern
Ernest Rutherford:
Proved the Plum Pudding Model was wrong!
Rutherford came up with a new model
of an atom, the electron cloud model:
A small, dense, positive nucleus
Electrons are outside the nucleus
Atoms are mostly empty space
Electrons are somewhere in this area +
Nucleus