1. Atomic Models: Democritus. All things were made of atoms and they were. indivisible. 1800 AD Dalton Atoms can not be broken into smaller pieces – atoms are like a. solid marble. All atoms of. an element were identical.

2. 1900’s Rutherford’s gold foil experiment http://www.shsu.edu/%7Echm_tgc/sounds/p ushmovies/l2ruther.gif - source of animation http://www.shsu.edu/%7Echm_tgc/sounds/p ushmovies/l2ruther.gif

3. History of Atomic Models Rutherford- all mass of an atom was in the center- the nucleus- discovered by gold foil experiment – Electrons surround nucleus and travel in orbits like planets around the sun – Problem: did not distinguish protons & neutrons and electrons do not actually move in the way he thought – http://www.chemsoc.org/timeline/pages/1911.html http://www.chemsoc.org/timeline/pages/1911.html

4. Rutherford and Bohr Bohr-electrons travel in a fixed orbit around the nucleus – Problem: electrons are actually in regions or clouds around the nucleus Difference between Bohr and Rutherford: – Rutherford said electrons travel in orbits like planets- problem- electrons also emit energy and should spiral closer to the nucleus – Bohr- only certain orbits are possible – they gain and lose energy as they move from one orbital to another Distiguished between protons and neutron while Rutherford did not

5. Current atomic model Electron Cloud Model- nucleus with protons and neutrons in the center – Electrons in clouds around the nucleus- very large area compared to the nucleus – Electrons move too fast to find exact location at any one time – Atoms are mostly empty space! http://www.teachersdomain.org/resource/phy03. sci.phys.matter.atoms/ http://www.teachersdomain.org/resource/phy03. sci.phys.matter.atoms/

6. Even protons, and neutrons are made up of smaller particles- quarks Quarks- smallest particles- make up protons, neutrons, and electrons- 6 types – up, down, top, bottom, strange and charm To study quarks- You have to accelerate charged particles to high speeds and cause them to collide with protons, breaking the proton Atoms

7. For now let’s stick to protons, neutrons, & electrons