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. 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 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

12. 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.

13. Early Theories

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

15. Current Theory