1. STAAR Ladder to Success Rung 2

2. John Dalton Dalton’s Four Postulates 1.Elements are composed of small indivisible particles called atoms. 2.Atoms of the same element are identical. Atoms of different elements are different. 3.Atoms of different elements combine together in simple proportions to create a compound. 4.In a chemical reaction, atoms are rearranged, but not changed.

3. J. J. Thomson (1903) Cathode Ray Tube Experiments – beam of negative particles Discovered Electrons – negative particles within the atom Plum-pudding Model

4. Ernest Rutherford (1911) Gold Foil Experiment Discovered the nucleus – dense, positive charge in the center of the atom Nuclear Model

5. Niels Bohr (1913) Energy Levels – electrons can only exist in specific energy states

6. Erwin Schrödinger (1926) Electron Cloud Model (orbital) dots represent probability of finding an e - not actual electrons

7. EM Spectrum LOWENERGYLOWENERGY HIGHENERGYHIGHENERGY ROYG.BIV redorangeyellowgreenblueindigoviolet

8. Calculations Example #1: If a particular green light has a wavelength of 4.9 x 10 -7 m, what is its frequency?

9. Example #2: The human eye can see light with a frequency about as high as 7.9 x 10 14 Hz, which appears violet. Calculate the energy that one photon of violet light carries.

10. Example #3: Find the energy of violet light if the wavelength is 4 x 10 -7 m.

11. Isotopes Atoms of the same element with different numbers of neutrons. Mass Atomic # Isotope symbol: “Carbon-12”

12. Average Atomic Mass weighted average of all isotopes on the Periodic Table round to whole number Avg. Atomic Mass

13. Avg. Atomic Mass Average Atomic Mass EX: Calculate the avg. atomic mass of oxygen if its abundance in nature is 99.76% 16 O, 0.04% 17 O, and 0.20% 18 O. 16.00 amu

14. The Orbitals s p d f

15. © 1998 by Harcourt Brace & Company s p d f 12345671234567 6767 Periodic Patterns

16. Lewis Dot Diagrams Dots represent the valence e -. EX: Sodium EX: Chlorine