1. Atomic Structure

2. Way Early Theories Democritus (460-370 BC)
First person to propose that matter is not infinitely divisible
Atomos
Matter is empty space through which atomos move

3. Way Early Theories Aristotle (384-322 BC)
Disagreed with the empty space idea
Rejected Democritus’s idea of atomic theory
Believed all matter was fire, earth, air, and water

4. Early Theories John Dalton (1766-1844 AD) All matter is made of atoms.
All atoms of a given element are identical and are different from atoms of other elements.
Atoms cannot be created, destroyed, or divided into smaller particles.
Atoms combine in simple whole number ratios to make compounds.
In a chemical reaction, atoms are separated, combined, or rearranged.

5. Early Theories J.J. Thomson (1856-1940 AD)
Worked with cathode ray tubes (CRT’s)
Deduced that the negatively charged particles flowing through the CRT were electrons…hence the first subatomic particle was discovered

6. Early Theories J.J. Thomson (1856-1940 AD)
Proposed a model of an atom to explain the neutrality of an atom
Plum Pudding Model

7. Early Theories

8. Early Theories Ernest Rutherford (1871-1937 AD)
Inadvertently disproved the Plum Pudding Model
Fired alpha particles (positively charged) at gold foil
Some alpha particles were deflected at huge angles

9. Early Theories Ernest Rutherford (1871-1937 AD)
Proposed that the atom had a tiny, dense central portion
Electrons move through empty space around the nucleus
Later stated that protons were in the nucleus

10. Early Theories James Chadwick (1891-1974 AD)
Proposed that the nucleus had another particle in it with a mass near that of the proton but with no charge

11. Early Theories Niels Bohr (1885-1962 AD)
Proposed a quantum model of the atom in which the electrons followed distinct orbits around the nucleus
It worked for H.

12. Early Theories

13. Current Theory Louis de Broglie (1892-1987 AD)
Proposed that the electrons traveled in wave-like orbits
Known as the Quantum Mechanical Model

14. Current Theory