ModernC

http://reich-chemistry.wikispaces.com/Fall.2008.MMA.Scolastico.Timeline

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 * (1) Identify the timeframe and context around the model in question. Include (cite your source!) an image of the model of the atom, and clearly describe the parts of the atom included in this model.**

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Time line: 1808

Many scientists have contributed to the atomic theory since those listed above. Some notable names are Einstein, DeBroglie, Schrodinger, and Heisenberg. Quantum theory has shown us that the electrons although they are particles also exhibit properties of waves. Now we think of the atom as a nucleus that is surrounded by probability clouds. The clouds represent the most probable locations of electrons. We still refer to these clouds as orbitals. The size and shapes of the orbitals may be calculated mathematically by using the equations for the waves


 * (2) Describe the experiment(s) that led to this model of the atom. How did evidence change the model of the atom compared to the previously accepted model?**

** The wave-mechanical model (electron cloud model) ** Electrons are in fact not moving like the planets around the sun but are located in regions (orbitals) in the empty space. The wave-mechanical model of the atom is required to explain the spectra of elements with multi electron atoms []


 * (3) Considering the modern view of the atom, what are the shortcomings of this model?**

The planetary model of the atom had two significant shortcomings. 1ST: unlike planets orbiting a sun, electrons are charged particles. An accelerating electric charge is known to emit electromagnetic waves according to the Larmor formula in classical electromagnetism; an orbiting charge should steadily lose energy and spiral toward the nucleus, colliding with it in a small fraction of a second. 2ND: the planetary model could not explain the highly peaked emission and absorption spectra of atoms that were observed.

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 * ) VALENTINE :)