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quantum mechanics.

ChrisNA
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Posted 08/28/02 - 05:35 PM:	#1
""In the early 20th century some experiments produced results which could not be explained by classical physics (the science developed by Galileo Galilei, Isaac Newton, etc.). For instance, it was well known that electrons orbited the nucleus of an atom. However, if they did so in a manner which resembled the planets orbiting the sun, classical physics predicted that the electrons would spiral in and crash into the nucleus within a fraction of a second. Obviously that doesn't happen, or life as we know it would not exist. (Chemistry depends upon the interaction of the electrons in atoms, and life depends upon chemistry). That incorrect prediction, along with some other experiments that classical physics could not explain, showed scientists that something new was needed to explain science at the atomic level. "" i pulled this off some essay / document i found on the web. Any thoughts on it?! i have a few, i want to see what others think.

Aniket
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Posted 08/29/02 - 03:19 AM:	#2
Originally posted by ChrisNA "For instance, it was well known that electrons orbited the nucleus of an atom. ." I dont think it was well known....After the discovery of positive nucleus, it was known that electrons lie somewhere outside the nucleus and are far away from it. So different plans were suggested. One of them was that electrons can stay in stable orbits around nucleus, which was proven wrong using classical methods.

xxuxx
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Posted 09/22/02 - 06:46 PM:	#3
Hi ChrisNA - If it's just the facts you want I have them, being a chemist myself (well, a chemistry student; I have made TNT before Very easy to make all you need is benzene, CH3Cl, AlCl3 to make toluene, and then you...oops sorry - seriously though, I made TNT under AR conditions in small quantities in an ice bath - whilst TNT is stable, other by-products of the synthesis are troublesome, one has to be especially careful of activating the benzene ring in more than one place, the resonance hybrid that results doesn't hold the NO2 groups very well). It was Neils Bohr, if my memory for trivialities serves me correctly, who first disproved the fixed electron orbits theory. He was studying the EM spectrum emissions of electrically excited hydrogen atoms at the time. You may already be aware of this, but, when you excite an electron to a higher energy state (this does not necessarily mean a position further or closer to the nucleus) the transition of that electron gives off a photon. Certain atoms and atomic/ molecular bonds have certain stabile energy configurations, so react in a very specific way when excited. Thusly, it is possible to identify an element by it's EM emissions. It is also possible to identify the various molecular bonds present, and the percentage composition of each of those bonds that makes up a compound, through very similar methods - gas chromatography and HPLC, and others. This gave way to Molecular Orbital theory, but that's another story altogether. Anyway, based on the fixed electron orbit model (analogous to the planets around the sun) Neils Bohr predicted the EM line emissions for all the various elements when electrically excited in their gas phase. The only EM line emission that he correctly predicted based on this model was the line emission of hydrogen. All of the other elements were different. So the only element that obeyed the fixed eletcron orbit model was hydrogen. All the rest were completely off. This left physicists hanging for a while, until Pauli and Heisenberg and a few others came along and refined an already probated electron orbital theory. Based on Pauli's exclusion principle Heisenberg came up with the uncertainty principle, and the orbitals became the probability we all know and have come to love .

ThatGirl
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Posted 10/11/02 - 10:01 PM:	#4
quantum mechanics is the branch of mathematical physics treating atomic and sub-atomic systems and thier interaction with radiation in terms of observable quantities. it's based on the idea that all forms of energy are released in discrete units- qaunta- but hey, we can discuss electron orbits and anti electrons and positrons all day and night- but wouldn't a little chit chat about alpha and beta decay versus gamma rays be more fun? photons, gotta love em.

xxuxx
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Posted 10/16/02 - 06:46 PM:	#5
Yeah, apparently Strontium-90 is pretty harmless unless you ingrest or inhale it. It gives of alpha particles, which don't penetrate the skin, however, Strontium-90 is a bone-seeking metal, and if absorbed rapidly causes luekemia. Hey, what did the blind, deaf quadruplegic get for his birthday? Leukemia

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