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{{mergeto|Atomic orbital|Talk:Electron cloud#Merger proposal|date=July 2008}} |
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{{about|the structure of an atom|the particle accelerator phenomenon|Electron-Cloud Effect}} |
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'''Electron cloud''' is a term used, if not originally coined, by the ] laureate and acclaimed educator ] in ] (] Vol 1 lect 6 pg 11) for discussing "exactly what is an ]?". This intuitive model provides a simplified way of visualizing an electron as a solution of the ], an advancement using the ] to surprising observations that could only be explained by introducing randomness. It is also often referred to as an orbital, because the two terms similarly conceptualize the space where an electron is likely to be found but cannot be actually pinpointed. In the electron cloud analogy, the ] of an electron, or ], is described as a small cloud moving around the ] or ], with the opacity of the cloud proportional to the probability density. |
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The model evolved from the earlier ], which likened an electron ]ing an atomic nucleus to a planet orbiting the sun. The electron cloud formulation better describes many observed phenomena, including the ], the ] and ], and atomic interactions with light. Although lacking in certain details, the intuitive model roughly predicts the experimentally observed ], in that electron behavior is described as a delocalized wavelike object, yet compact enough to be considered a particle on certain length-scales. |
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Experimental evidence suggests that the probability density is not just a theoretical model for the uncertainty in the location of the electron, but rather that it reflects the actual state of the electron. This carries an enormous philosophical implication, indicating that point-like particles do not actually exist, and that the universe's evolution may be fundamentally uncertain. The fundamental source of quantum uncertainty is an ] in physics. |
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In the electron cloud model, rather than following fixed orbits, electrons bound to an atom are observed more frequently in certain areas around the nucleus called ]s. The electron cloud can transition between ] states, and each state has a characteristic shape and energy, all predicted by the Schrödinger equation, which has infinitely many solutions. Experimental results motivated this conceptual refinement of the Bohr model. The famous double slit experiment demonstrates the random behavior of electrons, as free electrons shot through a double slit are observed at random locations at a screen, consistent with wavelike interference. ] accounts for this and, taken together with the double ], implies that an electron behaves like a spread of infinitesimal pieces, or "cloud", each piece moving somewhat independently as in a churning cloud. These pieces can be forced to coincide at an ] in time, but then they all must move relative to each other at an increased spread of rates to conserve the "uncertainty". Certain physical interactions of this wavelike electron, such as observing which slit an electron passes through in the double-slit experiment, require this coincidence of pieces into a lump-like particle. In such an interaction the electron "materializes", "lumps", or "is observed" at the location of one of the infinitesimal pieces, apparently randomly chosen. Although the cloud shrinks to the accuracy of the observation (if observed by light for example the wavelength of the light limits the accuracy), its momentum spread increases so that Heisenberg's uncertainty principle is still valid. |
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Physicist Adam Wagner speculates that, if visible, an electron cloud would look much like the static on a television screen. <ref>Allen, Stanley H. Photoelectricity - The Liberation Of Electrons By Light </ref> |
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== References == |
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<cite id=Feynman2006>* Feynman, Richard; Leighton; Sands. (2006). ''The Feynman Lectures on Physics -The Definitive Edition- ''. Pearson ]. ISBN 0-8053-9046-4</cite> |
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<cite id= Allen 2008>* Allen, Stanley H. Photoelectricity - The Liberation of Electrons By Light </cite> |
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