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Radioactive decay questions

  1. Feb 4, 2007 #1


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    I got some questions about radioactive decay:

    Do all atoms decay radioactive particles, only in a higher or lesser degree?
    I heard that atoms that have more protons (higher in the periodic system) than led, emit radioactive decay, and then stop at led. Does that mean that led does not emit radioactive decay? It would only make sense... Since there is matter that emit readioactive decay less than red, such as Radon.

    Ok, assuming that, will a hydrogen atom with one proton and one electron ever decay? If so, in what way excactly? It can't emit a heliumcore, since it doesn't have that, and it can't emit an electron, since it have no neutron.
    How will it decay?

    What in a material decides what form the radioactive decay will be? Either beta or alpha emission.

    And lastly, what happens to an atom after it decays? After an alpha decay, will it become an ion with [tex]e^-2[/tex] with two extra electrons. Or will these electrons just "fall" of the atom.
    Same for the beta decay, will it become a ion with [tex]e^+[/tex] ? I wonder what happens with the atom when it reestabilixe itself.
    Last edited: Feb 5, 2007
  2. jcsd
  3. Feb 4, 2007 #2


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    Not all atoms decay - there are many isotopes that are stable. Looking at the Chart of Nuclides (CoN) - http://www.nndc.bnl.gov/chart/ - the black squares show the stable isotopes. The heaviest stable nuclide is 83Bi209.

    An alternative CoN - http://wwwndc.tokai-sc.jaea.go.jp/CN04/index.html

    The nuclides (isotopes) on the upper side of the black squares decay by electron capture (EC) preferably or by positron emission - they are considered to have a deficiency of neutrons. The nuclides below or to the left of the black squares tend to decay by beta emission or when Z>82, alpha decay becomes a possibility.

    Nuclides heavier than lead (Pb) tend to decay by either alpha or beta decay, but some nuclides can go with either mode.

    See the decay series - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radser.html

    When an atom decays, the number of nucleons and electrons is conserved. In the case of beta decay, a neutron decays to a proton, electron and anti-neutrino. The ejected electron slows down among the neighboring atoms and mean while, the new atom with Z+1, simply grabs an electron from a neighbor, and successive atoms exchange electrons until the last one grabs the electron which escaped the original radionuclide.

    In alpha decay, the alpha particle slows down and becomes He by picking up two electrons. Meanwhile, the original atom which had Z, A is now a new element and nuclide with Z-2, A-4 and two of its atomic electrons leave. Between the alpha particle and the orignal atom, atoms exchange electrons thus maintain charge neutrality.
  4. Feb 5, 2007 #3


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    Thanks for your post, radioactive decay seems to be far more complex than I had imagined!

    I have a few questiosn though

    What does this mean? Is there other ways for an atom to decay than alpha and beta decay?

    I didn't understand this excactly. When the nucleus decays, (I assume the decayed atom core is the "Z+1", it grabs another electron from it's neighbours (greedy atom) and the neighbour atom does this in turn to HIS nighbour atoms? And then after a while the electron is grabbed by an atom, making this exchanging of electrons come to an end, (eventually). Was that correct?
    But then what happens if the electron escapes all other atoms, and flyes away, what happens to the other atoms, will they keep exchanging and grabbing electrons forever?

    The alpha decay explanation I understand, but then again, what if the alpha core flies away? Will the unwanted electrons be pushed away until they reach the "edge" of the concentration of atoms, and just pop out?
    But just one thing, what if the other atoms did not wish to have two extra electrons, will the electrons just "float" in between the atoms and then pop out?

    About the stable isotopes... Is it true that they will NEVER decay? I have heard that everything have a half-life, or a certain unknown time for it to decay into smaller parts. Even the proton and neutron decays (I believe). Why would not a stable isotope decay?

    Sorry about all my questions, but my teacher couldn't explain this.
    Last edited: Feb 5, 2007
  5. Feb 5, 2007 #4


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  6. Feb 5, 2007 #5
    It is thought by some that the supposedly stable hadrons themselves should decay with an absurdly long lifetime. To this end, there's a massive tank of liquid hydrogen on some research institute somewhere that's been sitting there for the last few decades looking for proton decays. None have been observed. It's not unfeasible to assume that ordinary protons bound in nuclei - if they can decay at all, could decay there and thus destabilise that nucleus.
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