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The Structure of the Atom

The Structure of the Atom. Atomic Theory Summary – the atom is the smallest particle of matter. History of the Atom Cont. JJ Thomson (1897) – Raison Bun Theory Electrons (negative) distributed in a positive sphere Cathode Ray Tube used to measure the mass of the electron

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The Structure of the Atom

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  1. The Structure of the Atom

  2. Atomic Theory Summary – the atom is the smallest particle of matter.

  3. History of the Atom Cont. JJ Thomson (1897) – Raison Bun Theory • Electrons (negative) distributed in a positive sphere • Cathode Ray Tube used to measure the mass of the electron Ernest Rutherford (1911) – discovered that atoms have a positive nucleus • Gold Foil Experiment • Positive charge due to protons

  4. James Chadwick (1932) – within the nucleus there are protons and neutrons (no charge) Niels Bohr – came up with the current model of the atom taught in Grade 9 and 10 Science; - Bohr Rutherford Model (planetary model)

  5. Bohr-Rutherford Model • Electrons move around the nucleus in circular paths called ORBITS / ENERGY LEVELS • Each Orbit / energy level can hold a specific # of electrons (always fill the closest orbit first and work out from the nucleus) • 1st – 2, 2nd – 8, 3rd – 8, 4th – 18 (2-8-8-18)

  6. Examples Mg He N Ne

  7. Summary of the Three Subatomic Particles • The Proton: - located inside the nucleus - is positively charged - symbol is p+ • The Neutron: - located inside the nucleus - has no charge (neutral) - symbol is no • The Electron - orbits outside the nucleus - very tiny compared to the proton or neutron - is negatively charged - symbol is e-

  8. Other Terms Atomic Number - the number of protons - unique to each atom, use it to identify an element Mass Number (Atomic Mass) - the number of protons plus the number of neutrons - measured in atomic mass units (amu)

  9. Since atoms are neutral (ie. No charge), the number of protons in an atom must equal the number of electrons Summary Atomic # = #p+ = #e- Mass # = #p+ + #no

  10. Read 179-190 (Ch 5.1 and Ch 5.2) • Questions pg. 186 2, 4, 5, 6 pg. 193 2, 3, 5, 7

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