1. Scientists The atom

2. Democritus - 400 BC- Greek philosopher - No experimenting -Matter made up of indivisible particles = “atomos”

3. Dalton 1801: Thomas Jefferson President 1802: John Dalton experimented and concluded…. 1806: Fall of Roman Empire

4. 1. Matter made up small particles= atoms Cant be created, destroyed, or made smaller 2. Atoms of same element are identical Different elements = different atoms 3. Chem. Rxn  atoms separate, join, or rearrange 4. Atoms of different elements can combine in whole number ratios: compounds. Dalton

5. 1850’s- Steam Steam powered engines of ships, trains, & factories Key Question’s of 19 th Century= “How to build more effective steam engines” and “ How to predict behavior of steam at high temps and pressures.”

6. 1896- Uranium - Uranium was found to emit strange energy: - Radioactivity: warm to the touch - Can unlock secrets to the atom

7. 1898- Marie CurieMarie Curie Concluded Uranium atom gave off radiation ( but another chemist discovered first) Found Radium – led to cancer fighting drugs Won two Nobel Peace Prizes Found Polonium Kept radioactive materials in her pocket Died of leukemia from radioactive materials

8. 1904-J.J. ThomsonJ.J. Thomson Plum Pudding Model/ Chocolate Chip Cookie Discovered electrons ( 1897) Experiment with cathode ray tubecathode ray tube – Particles move toward positive end – Particles must be negatively charged – Disproved that the atom was indivisible (could be broken into parts)

9. Thomson versus Rutherford

10. Rutherford’s Goldfoil Experiment Result: majority passed straight through some bounced @ large angles & straight back

11. 1911-RutherfordRutherford Discovered: – atom was mostly empty space – Atom had a dense positively charged center Disproved the Plum Pudding Model – (he was a grad student of Thomson)

12. 1913-BohrBohr Planetary model of atom Electrons move in an orbit Each orbit had a definite energy

13. 1914- 1918: World War I

14. 1926- SchrodingerSchrodinger Extension of Bohr’s model The electron “cloud” shows where the electron is most likely to be – You have a 90% chance of finding the electron Electrons move like waves

15. Quantum Mechanical Model

16. Dalton 1802 Thompson 1904- “plum pudding” Rutherford 1911 Bohr 1913 “planetary model” Quantum mechanical model History of Atomic Models

17. 1927- HeisenbergHeisenberg Uncertainty Principle Can not know the speed and the location of the e - at the same time

18. 1932-Chadwick Prisoner of war in WW1 Worked for Rutherford Discovered neutron Issue: mass of helium was 4 but it only had 2 protons

19. Summary Video