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Atoms

Atoms. Greek Atomic Model. Democritus (400 BC) Named the atom Atom cannot be divided. Dalton’s Atomic Theory. 1803 All elements are composed of atoms (not divisible) Atoms of same element are the same Atoms of different elements are different. Thomson’s Model. 1897

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Atoms

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  1. Atoms

  2. Greek Atomic Model • Democritus (400 BC) • Named the atom • Atom cannot be divided

  3. Dalton’s Atomic Theory • 1803 • All elements are composed of atoms (not divisible) • Atoms of same element are the same • Atoms of different elements are different

  4. Thomson’s Model • 1897 • Atom has smaller parts, like electrons • Atom made of a positive pudding-like material with negatively charged electrons scattered throughout

  5. Rutherford’s Model • 1911 • Positive-charged particles in the nucleus • Negative scattered around edges • Gold foil experiment

  6. Rutherford’s Experiment

  7. Bohr’s Model • 1913 • Electrons move in definite orbits around the nucleus (like the planets move around the sun) • Energy levels located a certain distance from the nucleus

  8. Compare the Thomson to the Rutherford/Bohr

  9. Wave Theory • Modern model • Electrons do not travel in definite paths • Think electron cloud

  10. Atomic Structure

  11. Subatomic Particles • protons = positive charge (+) • electrons = negative charge (-) • neutrons = neutral (0 charge)

  12. Subatomic Particles

  13. Lithium Atom • How many protons? • How many electrons? • How many neutrons?

  14. Atomic Number • identifies the element on the periodic table • equals the # of protons in the nucleus

  15. Atomic Mass • sum of the # of protons + # of neutrons in the nucleus • changes with isotopes

  16. Isotopes • atoms of the same element • same # of protons • different # of neutrons • different atomic mass • examples = hydrogen, carbon, uranium

  17. Isotopes

  18. Electron Cloud • electrons move about the nucleus locked in a certain area of the electron cloud • location called energy levels

  19. Electron Shells

  20. # of electrons in each orbital shell • electrons with low energy are found in the energy level closest to the nucleus

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