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The Life of Atom

The Life of Atom. http://www.youtube.com/watch?v=hhbqIJZ8wCM. Birth. In 1809 Dalton came up with the first picture of the atom. Tiny indestructible sphere. Childhood. In 1897 Thomson discovered very light weight negatively charged particles (electrons)

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The Life of Atom

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  1. The Life of Atom http://www.youtube.com/watch?v=hhbqIJZ8wCM

  2. Birth • In 1809 Dalton came up with the first picture of the atom. • Tiny indestructible sphere

  3. Childhood • In 1897 Thomson discovered very light weight negatively charged particles (electrons) • Chemists determined that the negative charge must be balanced by a positive charge: the raisin bun model

  4. Adolescence • In 1911 Rutherford published the results from the gold-foil experiment

  5. The Results… • Until now atoms were thought to be solid • Most of the alpha particles went right through the foil • Some alpha particles curved when they went through • Only a few alpha particles deflected back (which is what was expected)

  6. Gold-Foil Conclusions • The atom is made up of mostly empty space • Alpha particles are positive and curved when they got too close to the small nucleus • Only alpha particles that hit the nucleus got deflected back (rarely happened so must be small)

  7. Teen Years • Entirely positive nucleus would explode (+ charges repel) • The total mass number of the atom could not be accounted for • In 1932 Atom gets a girlfriend…the neutron is discovered!

  8. Rutherford’s Model of Atom • The nucleus is small and made up of protons and neutrons • The electrons circle around the nucleus

  9. Trouble in paradise? Rutherford’s model doesn’t quite work • Electrons should lose energy and crash into the nucleus but this doesn’t happen • 19th century physics dictates that a body in motion must continuously give off energy- seen as a continuous spectrum through a spectroscope- but we see a line spectrum

  10. Bohr’s Addition to Atom • In 1913 Bohr explains why a line spectrum is seen instead of a continuous spectrum • Electrons are only giving off certain frequencies of light • Electrons travel in defined spaces called orbitals, which have defined energy

  11. How does a line spectrum say all that? • When an electron is excited it jumps from one orbital to a higher one • The electron does not stay excited and eventually goes back to its ground state (original orbital) • A wave of light is emitted (photon) from this process which can be seen as a line on a line spectrum

  12. Problems with Bohr’s Theory • Bohr couldn’t explain why lines appeared in ones, threes, fives and sevens • Physicist Max Planck supported Bohr’s idea that atoms can absorb or emit only discrete quantities of energy called quantums • Einstein called these packets of energy photons

  13. Adulthood • In 1926 Schrodinger derived the quantum mechanical model of the atom • Described atoms as having wave-like properties which came from de Broglie’s hypothesis • Mathematically determined the shape of the orbitals and the probably of an electron being in a certain place at a certain time- orbitals are not just spheres anymore

  14. In 1927 Heisenburg stated: Although the shape of the orbital is predictable, the exact location of an electron cannot be determined. This is the Heisenburg uncertainty principle

  15. Quantum Theory • Quantum is the new and improved Bohr-Rutherford model • Model shows electron placement and helps to determine valence electrons and stability of the atom • Each orbital can hold a maximum of 2 electrons

  16. Orbital Shapes and Orientation S is a sphere shape • 1 orientation = 1 orbital = 2 electrons P is a figure 8 or dumbbell shape • 3 orientations = 3 orbitals = 6 electrons

  17. D orbitals have a clover shape • 5 orientations = 5 orbitals = 10 electrons

  18. F orbitals have many shapes • 7 orientations = 7 orbitals = 14 electrons

  19. Rules for Quantum • Aufbau Principle - each electron is added into the subshell with the lowest energy orbital available • Hund’s Rule - Each orbital subshell gets a single electron first and then electron can pair. All electron are ‘up’ when single • Pauli Exclusion Principle - no electron can have the same 4 quantum #s in an atom - electron sharing an orbital have opposite spins

  20. Quantum Number Principle quantum number ‘n’ • Describes the orbital’s energy level and relative size Orbital shape quantum number ‘l’ • Describes the orbital’s shape, energy of subshells Magnetic quantum number ‘ml’ • Describes the orientation in space Spin quantum number ‘ms’ • Describes the behaviour of a specific electron in an orbital

  21. Summary of Quantum numbers of electrons in atoms

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