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Download Mrs. Jiménez’s Abbreviated Version of Atomic History for Study Purposes
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Mrs. Jiménez’s Abbreviated Version of Atomic History for Study Purposes Scientist Democritus Dalton Thomson Rutherford Main Discovery Atoms are “indivisible” Atomic Theory of Matter Proposed: 1 – All elements are composed of atoms 2 – All atoms of the same element are exactly alike 3 – Atoms of different elements are different (different mass) 4 – Compounds are made by joining two or more atoms of the same or difference elements Discovered electrons and that they are NEGATIVELY charged subatomic particles in a neutral atom. Therefore, there must be some positive and counteracting charge in the atom. He proposed the “plum pudding model,” whereby electrons were moving about in a “sea” of positive charge. Dense, but small, positively charged and centrally located atomic nucleus. Most of the atom is empty space. Chadwick Bohr Shrodinger Discovered the neutrons, which exist so that positively charged protons will not repel each other so as to explode out of the nucleus. Proposed that electrons travel at fixed distances from the nucleus in an atom such that they orbit the nucleus much like planets orbit the sun. He also proposed ideas for how electrons could absorb energy to become excited and then fall back to ground state configuration. Proposed the cloud model of electron location probability. This describes the likelihood of finding an electron in a given orbital. Experiment/Model Word “atomos” means indivisible in Greek Atomic Theory of Matter Cathode Ray Tube Experiment - discovered that by passing an electric current, a cathode ray beam would be created. This cathode ray was attracted to a positive electrode and repelled by a negative electrode, indicating that the cathode ray was composed of tiny negative particles that he later called electrons Plum pudding model or Chocolate chip cookie model Gold Foil Experiment https://www.youtube.com/watch?v=_uEFKG122dA -shot positively charged alpha particles at foil containing gold atoms. Most passed right through indicating that atoms are mostly empty space. A very small amount were shot directly backwards because they were repelled by the + nucleus. 1-5 Words Indivisible Atoms Atomic Matter Theory Negative Electrons, Plum Pudding, Positive Small Nucleus, Gold Foil Neutrons Planetary Model Electrons in Orbit, Planetary Model Electron Cloud Model Electron Cloud Model BOHR’S PLANETARY MODEL
