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Atomic Model Evolution (Webquest) Directions: Research and look up the many experiments on that have lead to the current model of the atom. If you feel this sheet will not give enough room you can set this up in your lab-book without using this page. Be as clear and specific as you can. When complete please tape into lab-book for future reference. LT: IWBAT describe the evolution of the atomic model, which includes stating how the scientists knew they were right (evidence vs inference). Name of Scientist/Year/Name of Experiment Democritus ~460BC John Dalton 1803 “Various Experiments with Vapor, Temperature and Pressure” Observations/Evidences from Experiment Inference(s) (What did they learn?) -no experiment done -he philosophized that all matter was made up of small units that couldn’t be broken down any further while maintaining the same properties, he called each small unit an “Atom”. - he predicted the Atom was a solid ball with no electrical properties (no positives or negatives) 5 Points to Atomic Theory…. (explain each) 1) all matter is made up of atoms 2) all atoms in a given element are identical 3) atoms are indivisible/industructable while still maintaining the same properties 4) a chemical reaction is a rearrangement of atoms that come in specific ratios (compounds are made up of 2 or more atoms) Picture of Atomic Model JJ Thomson 1898 “Cathode-Ray Tube Experiment” Ernest Rutherford 1911 “Gold Foil Experiment” Stream of particles that attracted to a positive plate and repelled the negative plate He took helium atoms (alpha rays--positive) and shot it at a piece of gold foil 1) some particles went straight through 2) some particles bounced back but to the sides 3) some particles bounced straight -the stream of particles had a negative charge -atoms have a particle that is small and negative “electron” *Plum-Pudding Model* 1) atoms have a dense nucleus that is positive 2) atoms are made up of mostly empty space back Niels Bohr 1913 “Spectroscope and Spectrum Lines” James Chadwick 1932 “______________” Erwin Schrodinger 1933 “______________” He looked at element tubes and drew the spectrums for many different elements 1) that each element has different numbers of electrons and the electrons are on different energy levels He did many radiation experiments, he took polonium and smashed with beryllium -He found the neutron -Mathematical formulas are used to match the kinds of data that was being observed. -Mix geometry with statistics Inferred: that electrons don’t orbit the nucleus, they move like waves in an electron Quantum Mechanical Model – several scientists *the current model cloud.