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What Causes an atom to decay?

  1. Jul 20, 2006 #1
    What causes an atom to decay? To tell you the truth, it doesn't even have to be an atom, it can be a proton, a neutron, an electron. My question really is what causes a life to end. I know everything has a life but why? Energy doesn't have a life. Then why can't an atom live forever? Ok, if it is being provided a theoretically perfect environment which would ensure that nothing damages it, then would it life forever?

    I heard that we have technology now to keep humans alive for a 1000 year but you will have to be locked in a room, no radiation, no scratches, good circulation, heartbeat, etc., will be ensured. Sorry off the topic, just felt like sharing, might be a rumor.
    Last edited: Jul 20, 2006
  2. jcsd
  3. Jul 20, 2006 #2


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    The decay of various atomic nuclei (also neutrons) is completely unrelated to questions concerning the death of living creatures.

    The atomic nuclei situation is relatively simple to answer. It is a question of allowable transformations and energy levels. For example neutron decay into proton and electron (and anti-neutrino) gives off energy. The resultant particles are all stable (some theoretical question about protons, but no experimental evidence showing it is not stable) and don't decay into anything else. Some atomic nuclei are stable and some are not for the same basic reason.
  4. Jul 20, 2006 #3
    Perhaps this thread should be moved...
  5. Jul 20, 2006 #4
    I took care of unrelated stuff, you explained me what it turns into after it decays but you didn't tell me WHY it happens or what causes it to?
  6. Jul 20, 2006 #5
    one way to look at it is to say that your particle wants to be at the lowest potential energy state - called the ground state, there are local minima - these are the the "unstable" states (though they sometime can be quite stable - an example would be the Deuterium atom).

    for example - a neutron on its own would decay because the potential energy of a proton, electron and anti-neutrino is lesser then it's energy (they have less total mass).

    on the other hand - a neutron will have very little chance to decay if it's connected to a proton (Deuterium) - in this case the energy of the resulting system would be greater then the existing one - because two protons very close to each-other have lots of potential energy.
  7. Jul 21, 2006 #6
    I think you are looking for Beta Decay, which is where an atoms sheds an electron.

    If you consider that the heavy elements are built up in stars from Hydrogen, Deuterium and Helium in nuclear reactions, you can see how without a source of energy, they slowly decay back into the most basic of atoms. Some atoms are naturally more stable then others and thus take longer to decay.

    As for human decay, its not the atoms themselves that decay when we die, its the molecular bonds between the atoms that are broken down by a variety of means like, micro-organisms, EM radiation, and even trace amounts of nuclear decay.

    Would an atom decay if in a theoretically perfect environment? I suspect that depends on what atoms you are talking about, I am no expert, but I'd guess that a Hydrogen atom would not decay since its the lightest element.
  8. Jul 24, 2006 #7
    Let's look at what's typically involved in the process of "alpha-decay" of a heavy nucleus.

    We have a "mother" nucleus (A) which decays into a "daughter" nucleus (B) and an "emitted" alpha-particle (α):

    A → B + α .

    A simple (approximate) way to treat this kind of problem is to think of A as though it already consists of B and α. So, we put B at the center of our space, and we put α at a distance r away from B. Then we consider the potential energy V, of α in the vicinity of B, as a function of r (the distance between them); we write this function as V(r).

    Here is a sketch (click here) of what is typically found. The potential-energy function V(r) has the form of a very deep "well" (the region r < ro), with a peak value equal to Vo at the edge (r = ro) of the "well". Outside of the "well" (r > ro), the potential energy V(r) gradually falls off.

    In the sketch, the energy Eo represents the typical total energy of the α-particle. As you can see, when the α-particle is situated inside the "well" (r < ro), it does not have enough energy to escape. On this basis, then, we would expect to find that – in an 'ideal' environment – the "mother" nucleus A is stable. As you wrote:
    Your suspicion would be correct if the system in question behaved according to "classical" mechanics, the mechanics of Newton. In that case, a "theoretically perfect environment" (in which the α-particle never gets a "kick" hard enough to raise its total energy high above its typical value Eo and up over the "peak" Vo of the "well") would result in a perfectly stable "mother" nucleus A.

    But, as it turns out, the system in question behaves according to "quantum" mechanics. In that case – even when there is a "theoretically perfect environment" (so that the α-particle always has a total energy equal to Eo) – the α-particle can still make its way to the outside of the "well". This phenomenon is referred to as quantum mechanical "tunneling" or "barrier penetration".

    Quantum mechanically, then, an α-particle situated inside the "well" will have a certain probability (per unit time) to be found outside of the "well". And this gives rise to the familiar (exponential) law of decay.
  9. Jul 25, 2006 #8
    Ok I sorta get it, if someone would just reexplain me in a diff. manner, it would be kicked in my head, its one of those things that if one of you were in front of me, talking to you about it would do it.

    Ok, I mean I don't get the quote above. Why would the neutron decay? Why does it care about the energy around it? I am sorry if I am talking like a beginner, I havn't taken chem in a year, I am going to take chem ap this year so I need to get this stuff reviewed.
  10. Jul 27, 2006 #9
    I'm not sure how far back we'll have to go.

    ... Tell me, do these two sketches (click here) mean much to you?

    Attached Files:

  11. Aug 6, 2006 #10
    I think you may be looking for the idea that all processes in nature decay into simpler forms (lower energy) when external forces are left out of interfering with the system. For example, a golf ball dropped from the CN tower falls because its at a lower energy while on the ground than at the top where the graviational potential gives it a greater energy. But, if there were an extremely powerful updraft the golf ball might hover or even rise (this would be the external force that we want to leave out of the system for simplicity).
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