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Author Topic: When an alpha particle is emitted, what happens to the atom that emits it?  (Read 8726 times)

Offline warmare

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If an radioactive element radiates alpha particles, it is said the helium nuclei is released which ofcourse means that 2 neutrons and two protons have escaped. My question is that what about the two electrons which left behind with the radiated atom, if these electrons are with radiated atom then it must be an ion left behind. i am surprised about these two electrons.........
« Last Edit: 20/05/2008 20:39:14 by chris »


 

Offline Bored chemist

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Initially, the nucleus left behind is present as an ionised species. Also, the electrons round it are all "in the wrong places". They cannot instantly move from the energy levels of, for example uranium to those of thorium. Shortly after the alpha particle is emited other radiation is emited too as the elctrons settle down.
In due course the helium nuleus that emited picks up a couple of electrons (not necessarily the same ones as before) and the ionised thorium loses a couple of electrons to its surroundings.

There is one weird and not enormously useful way of using this efect. One of the first syntheses of perbromates relied on beta decay of a selenate. In most cases the SeO4-- ion was smashed by the reaction but ocasionally it gave BrO4-

The simple answer is that the energy released ny the nuclear decay is of the order of a million times bigger than that needed to ionise the molecule. The electrons just get knocked about and have to settle themselves back down later.
 

Offline chris

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Ian Farnan, from Cambridge University, published some very elegant work in 2007 looking at what happens to atoms as alpha particles are emitted.

By using NMR (nuclear magnetic resonance) he was able to show that when an alpha particle leaves a plutonium nucleus, creating an atom of uranium-235 in the process, the uranium nucleus recoils like a gun. This sends it cannoning into the surrounding atoms and damages the crystal structure of the surrounding material. Each alpha decay, he found, therefore knocks about 5000 other atoms off kilter.

This had previously not been appreciated, and is also a major consideration for the long-term storage of spent radioactive materials, which are traditionally turned into ceramics. Given what Ian Farnan has shown, these effects could make the ceramics very leaky within a few hundred years, which is significantly less than the few hundred thousand years that the material remains radioactive and therefore a threat.

http://www.thenakedscientists.com/HTML/content/interviews/interview/655/

Chris
 

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