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Atomic Models

Atomic Models. The Greeks. Ancient Greeks – Naturalism, a physical explanation for phenomenon. Democritus – In 450 BC proposed atoms, particles that could not be further divided. Aristotle – Earth, Air, Water, Fire. Aristotle, just remember … Earth, Wind, and Fire (& Water).

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Atomic Models

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  1. Atomic Models

  2. The Greeks • Ancient Greeks – Naturalism, a physical explanation for phenomenon. • Democritus – In 450 BC proposed atoms, particles that could not be further divided. • Aristotle – Earth, Air, Water, Fire.

  3. Aristotle, just remember…Earth, Wind, and Fire (& Water). Do you rememberthe 21st night of September?Love was changing the minds of pretenderWhile chasing the clouds awayOur hearts were ringingIn the key that our souls were singing.As we danced in the night rememberhow the stars stole the night awayBa de ya - say do you rememberBa de ya - dancing in SeptemberBa de ya - never was a cloudy day

  4. Lived from 1766 - 1844 • Believed atoms had no internal structure. • Atoms differ only in mass and size. • Looks like… (Think spheres). John Dalton

  5. Lived from 1856 - 1940 • Atoms are divided into p+ and e-. • Atoms have an internal structure. • Looks like… (Think ‘plum pudding’). J.J. Thomson

  6. Lived from 1871 - 1937 • Atoms have a nucleus containing p+. • e- moved around the nucleus. • Looks like… (Think ‘planets’). Ernest Rutherford

  7. Full professor at McGill at the age of 26. Ernest Rutherford

  8. Lived from 1891 - 1974 • Nucleus also contains no, neutrons • no prevent atoms from splitting up by increasing the strong force without increasing the charge in the nucleus. • Looks like… (Think ‘neutrons’). James Chadwick

  9. Lived from 1885 - 1962 • Electrons have distinct energy levels or shells around the nucleus. • Looks like… (Think ‘electron shells’). Neils Bohr

  10. The nucleus occupies a tiny part of an atom. It’s diameter is roughly 10-12 cm, whereas the diameter of the entire atom is between 2 x 10-8 cm and 5 x 10-8 cm. • There are other particles besides e-, p+, no including hadrons, leptons, mesons, quarks, neutrinos, and hyperons. Nucleus • Each has its own counterpart (e.g. antiparticle of an electron is a positron). • When particles collide with their antiparticle, they annihilate each other, releasing vast amounts of energy at a subatomic level. • When a positron and electron collide they produce one million electron volts of energy (MeV = 1.6 x 10-13 joules).

  11. Completes billions of trips around the nucleus in a million’th of a second. • Travels 1600 times slower than the speed of light. • Outer shell e- ’s determine the chemical behavior of an element. • Mass = 9.11 x 10-28 grams Electron, e-

  12. 1840 times heavier than an e- (1.67 x 10-24 grams). • The number of p+ equals the number of e- to insure the stability of an atom. Proton, p+

  13. Has no electrical charge. • Essentially the same mass as a p+ (1.67 x 10-24 grams). • no ’s prevent the nucleus from splitting apart. Neutrons, no

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