2. Atomic Structure- History

3. Philosophers and Scientists Know how the following contributed to the history of the atom: Philosophers from History of the Atom video –Empedicles - four “elements” – earth, water, fire, air. –Leucippus - t he first Greek to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms –Aristotle - five elements – earth, air, fire, water, and aether

4. Next week

5. Modern Day scientists –Dalton atoms could not be divided all elements of a given element are the same different atoms could join to form compounds –Thomson the plum pudding model negatively-charged "plums” surrounded by positively-charged "pudding” –Rutherford http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf atom is made up of a central charge surrounded by a cloud of orbiting electrons –Bohr electrons are in levels around the nucleus

6. Structure of the Atom

7. ParticleChargeMass (atomic mass units) Location Protonpositive + 1nucleus Neutronneutral Ø 1nucleus Electronnegative - 0.0006orbit, level, cloud

8. The Nucleus

9. A 1946 test of an atomic bomb in the lagoon at Bikini atoll. The explosion has just started; surplus ships moored nearby can still be seen.

10. http://video.google.com/videosearch?source id=navclient&rlz=1T4SUNA_enUS316US3 16&q=atomic%20bomb&um=1&hl=en&ie =UTF-8&sa=N&tab=iv# http://www.youtube.com/wa tch?v=bw85r24WW3s

11. The nucleus –the center of the atom composed of protons and neutrons –held together by four forces (electromagnetic, strong, weak, and gravity) –99.9% of the atom’s mass is here –about 100,000 times smaller than the entire atom –the atomic number of an atom is the number of protons in the nucleus –the atomic mass or mass number of an atom is the sum of the protons and neutrons

16. –Isotopes atoms with the same number of protons (and therefore the same element) but with a different number of neutrons.