1. History of the Atom

2. Greek Philosophers Time Period: 200 B.C
Democritus: Greek philosopher
who first proposed the idea of a small indestructible particle that composes all matter
Democritus called this building block the ATOM

3. The Greek Philosophers
Democritus
Aristotle
Greek Philosopher
Matter must be small, hard particles which were indivisible
A point where it ends
Greek Philosopher
Matter was continuous
Table (chop forever)

5. John Dalton Time period: 1800’s
The first individual to propose an atomic theory based on experimentation

6. John Dalton Time period: 1800’s
All matter consists of tiny particles. Dalton, like the Greeks, called these particles.
2. Atoms of one element can neither be CREATED or changed into atoms of any other element.

7. John Dalton
3. All atoms of the same element are THE SAME in mass, size and other properties. 4. Atoms of one element ARE DIFFERENT IN SIZE, MASS, AND PROPERTIES from atoms of other elements.

8. John Dalton
5. In COMPOUNDS, atoms of different elements combine in simple, whole number ratios.

10. Thomson Time Period: 1900’s
Description of Experiment
Cathode Ray Tube
Rays appear on a screen
Thomson looked to see how a magnet affected the rays

11. Thomson Time Period: 1900’s
What happened?
Negative side of the magnet repelled
Positive side of magnet attract

12. Thomson Time Period: 1900’s
Conclusions from the Cathode Ray Tube (CRT)
Atom has a negative particle called the ELECTRON
Analogy for model: Chocolate Chip Cookie (Plum Pudding)

13. J.J. Thomson

14. Goals To Accomplish Today 10.30.12
Lecture: History of the Atom
(A) Atomic Time Line Worksheet
Atomic Anagram Worksheet

15. Ernest Rutherford Time Period: 1911
Description of experiment
GOLD FOIL EXPERIMENT

17. Ernest Rutherford Time Period: 1911
What happened?
Most alpha particles went through
Some deflected at different angles
Some bounced right back

18. Ernest Rutherford Time Period: 1911
Conclusions
Atom is mostly empty space where the electrons move
Mass is concentrated in the center (NUCLEUS)
Nucleus is positive

19. Ernest Rutherford Time Period: 1911
Analogy for Model: PEACH
Picture:

20. Bohr’s Model of the Atom Time Period: 1913
Description of Model:
Electron in energy levels and can jump from level to level
Electrons travel in fixed and definite paths
Close to the nucleus the lower the energy

21. Bohr’s Model of the Atom Time Period: 1913
Analogy: PLANETS
Picture:

22. James Chadwick Time Period: 1932
Discovered the neutral subatomic particle in the nucleus: NUETRON

23. Quantum Mechanical Model Schrodinger and Heisenberg Time Period: 1926
Description:
Electrons do not travel in specific paths
No definite shape
Location of electrons are all a probability

24. Quantum Mechanical Model Schrodinger and Heisenberg Time Period: 1926
Analogy: FAN AT HIGH SPEED
Picture: