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Atomic Theories and Models Atom: Atomic Theory: Theory John Dalton Year: His atomic model stated that: 1) 2) 3) 4) Michael Faraday Year: - Discovered atoms can gain electric charges and form charged atoms called _________ - In this modified version of Dalton’s model, he said: 1) 2) 3) Model Analogy J.J. Thomson Year: - His “raisin bun” model explained: 1) Atoms contain particles called _____________________ 2) Electrons have a small mass and __________ charge 3) The rest of the atom is a sphere of ____________ charge 4) The electrons are embedded in this sphere, so that the resulting atoms are ________________ or uncharged. H. Nagaoka Year: - Modeled the atom as a large _________________ sphere surrounded by a ring of negative __________________ - He did not talk about protons or neutrons Ernest Rutherford Year: - He tested Thomson’s and Nagaoka’s models by aiming alpha particles at a thin sheet of gold foil. He thought the particles would all pass through but a very small amount bounced straight back. - To explain his results, he came up with the nuclear model: 1) An atom has a tiny, dense, positive core called the _____________ (which deflected the alpha particles and contains ___________________) 2) The nucleus is surrounded mostly by empty space, containing rapidly moving negative ___________________ (through which the alpha particles passed through) Niels Bohr Year: - He developed this model to explain where the electrons go around the nucleus. - In his diagrams, the symbol of the element is written in the center to represent the nucleus - A series of circles is drawn around the nucleus to represent the orbits, and electrons are shown in these orbits Bohr-Rutherford Diagrams - a combination of Rutherford’s nuclear model with Bohr’s planetary model - it summarizes the numbers and positions of all three subatomic particles in an atom - a circle is drawn in the center to represent the nucleus. The numbers of protons and neutrons are written in this circle - electrons are again shown in circular orbits around the nucleus