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Where do the electrons go?

  1. Jul 7, 2010 #1

    kelvin490

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    In an alpha decay, an helium nucleus is emitted and the daugther becomes less in number of protons and neutrons. Does this daugther carries excess number of electrons so that it exists in the form of an ion? If not, where do the electrons go?

    For example, when U decays into an Th and an alpha particle, does the Th exists as an ion?
     
  2. jcsd
  3. Jul 7, 2010 #2
    I guess it does exist as an ion for a fraction of second and then loses its two surplus electrons to the surroundings.On its passage through the air the alpha particle creates more ions by collision and this will be followed by ion recombination.Eventually the alpha particle will be too slow to create further ions and it will gather up two of the spare electrons and change to a helium atom.Throughout the event charge is conserved so I suppose you could describe this by saying that at the start of the event the parent atom loses an alpha particle and two electrons and at the end of the event two electrons attach themselves to the alpha particle.
     
  4. Jul 8, 2010 #3

    kelvin490

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    Does it imply that radioactive energy is also released in the form of electrons' kinetic energy?
     
  5. Jul 9, 2010 #4
    I think so kelvin.From momentum considerations the alpha particle gets the bulk of the KE and the remainder is picked up by the rest of the system this including the two electrons.

    You asked a brilliant question and I would be interested to hear yours or any other views.I did a search and found nothing.
     
  6. Jul 10, 2010 #5

    kelvin490

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    Thank you Dadface. Most textbooks mention that the energy converted from the lost mass in radioactive decay are in the form of gamma ray, KE of alpha and Beta particles etc. but surprisingly they seldom mention about the KE of the excess electrons in the daugther, and none of them talk about whether they exist as atom or ion.
     
  7. Jul 10, 2010 #6

    Astronuc

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    The alpha particle slows down in the surrounding matter and becomes a helium atom. Two electrons would leave the vicinity of the new atom and go in search of an excess of + charge, which would be in the direction of the alpha particle. The alpha particle excites and ionizes atoms along its path until it comes to rest as a helium atom. There is a cascade of electrons more or less along the alpha trajectory. In the end, the charges balance - i.e., there are no new charges, + or -, created.
     
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