People, Experiments, Conclusions. Democritus – Ancient Greeks (5th century B.C.) believed in a small, indivisible particle – “atomos” Dalton – Modern.

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People, Experiments, Conclusions

Democritus – Ancient Greeks (5th century B.C.) believed in a small, indivisible particle – “atomos” Dalton – Modern theory (1803)– indivisible atom J.J. Thomson – Plum Pudding model (1897); Used Cathode Ray tube to experiment; Atoms have identical, removable (- ) charged particles. http://highered.mcgraw- hill.com/olcweb/cgi/pluginpop.cgi?it=swf::100%25::100%25 ::/sites/dl/free/0072512644/117354/01_Cathode_Ray_Tube.s wf::Cathode%20Ray%20Tube

Millikan (1909) – Oil Drop experiment to determine the charge on electron and mass of electron. Ernest Rutherford (1911) – Gold Foil Experiment – Discovered nucleus as dense (+) charged center. http://micro.magnet.fsu.edu/electromag/java/rutherford/ Niels Bohr (1913) – Electrons in orbit around the nucleus – based on work with Hydrogen. http://www.dlt.ncssm.edu/tiger/Flash/phase/ElectronOrbits. html

 Erwin Schrodinger (1926) – Quantum theory – treats electrons as waves.  Quantized energy levels.  No exact “path” for electrons – just a probability of location for the electrons in an area.  Electron Cloud – picture of probability  Surface of cloud gives approximate shape and 90% chance of e - location (Fig 13.2 in text)

 Quantum “numbers” - describe electrons  Principal Quantum Numbers:  n = 1, 2, 3, 4, 5  n = principal energy level  Angular momentum Quantum Number  In “English” – sublevel within each energy level.  Each sublevel has a different shape.  Current sublevels: s, p, d, f  orbitals no g orbitals no g  orbitals with g orbitals with g

 Magnetic Quantum Number  Deals with distribution inside the sublevel.  Orientation along the axes.  Spin Quantum Number - +1/2 or -1/2

 Electron distribution  Max # of e- in any given energy level is = 2n 2. (n=energy level)  Level1234567 Max e-2818 Sublevels sss Availablepp d

 Orbitals – areas within the sublevel where electrons can “hang out”  Each orbital can hold 2 electrons Sublevel# of orbitals# e- s1 2 p3 6 d5 10 f7 14

Electron Configurations Sample: N = Say: one “s” two, two “s” two, two “p” three

More Examples - C – F – Li – Mg P

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