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How does an atoms life end?

  1. Dec 4, 2013 #1
    How does an atoms "life" end?

    Two stupid questions. What "force" keeps the electrons spinning around the nucleus in an atom, and how does an atom eventually "die", or wear out? Thanks for a serious answer, I really have no idea. :frown:
  2. jcsd
  3. Dec 4, 2013 #2
    The electrostatic, or coulomb force. The proton has a positive charge, and the electron a negative charge, so they attract each other. I don't know what you mean when you say that the atom "dies".
  4. Dec 4, 2013 #3


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    The electromagnetic force, of which the electrostatic is a manifestation of, keeps atoms together. Atoms do not wear our and die. Certain combinations of protons and neutrons in the nucleus of an atom can cause it to decay, but this is a result of the interplay between the EM force and the Strong force, which is what holds protons and neutrons together in the nucleus. Practically all matter you see around you is stable and does not decay or wear out.
  5. Dec 4, 2013 #4


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    I don't think there's any answer for the life and death of an atom. Electrons are free to move around so given enough heat the electron will move to other nucleii... Also atoms crushed in a neutron star will transform into individual neutrons so in a sense they would cease to exist as atoms. And then there's radioactivity where unstable nucleii shed alpha particles and neutrons so the atoms are in essence falling apart. And then there's fusion where new atoms are created from smaller ones.
  6. Dec 4, 2013 #5
    In some theories, protons decay after some very long time. That means atoms will cease to exist.

    In other theories, if the universe is expanding fast enough, everything, including atoms and nuclei will be eventually torn apart.

    But I do not think any of these theories have any solid confirmation, so it is probably correct to say that we do not know the ultimate fate of atoms at this stage. The theories that we believe confirmed so far indicate that at least some atomic configurations can be stable forever.
  7. Dec 5, 2013 #6
    I really appreciate the answers!

    What "force" keeps the electrons spinning instead of falling in to the nucleus then? And yes, I guess atomic decay was my question.

    Very cool about a nuetron star! So there are no atoms in a neutron star? I would take it the same could be said of a black hole because the gravity is even stronger? Thanks again for any answers or information, it is greatly appreciated I assure you!
  8. Dec 5, 2013 #7
    The force is called the Coulomb force. It has to do with the nucleus being positively charged and the electron being negatively charged.

    An atom and the subatomic particles within it are not something that we can really visualize. At that small of a scale, everything is different. An electron is not "spinning" around a nucleus, we only say that because of some properties it has. In reality though, the electron doesn't even exist in a specific place at a specific time. It's not a classical physical object that is always somewhere and always has some sort of definite state. It behaves differently than that.
  9. Dec 5, 2013 #8
    According to classical electrodynamics, electrons spinning about the nucleus must radiate electromagnetic waves, lose energy and so spiral into the nucleus. That does not happen, which, soon after it was established that electrons orbit nuclei, led to the development of quantum mechanics.

    According to which, electrons in the vicinity of the nucleus cannot spiral in; they can only be in some particular closed orbits, and jump up and down from orbit to orbit, and there is a particular orbit closest to the nucleus, from which they can only jump up.
  10. Dec 5, 2013 #9
    There are 4 fundamental forces in Nature.

    Gravitational: that everyone knows well but have (almost) nothing to do in acting directly with the atoms.
    Weak and Strong nuclear force.
    Electromagnetic force (that is not just Coulomb! but Coulomb + Lorentz + ElectroDynamical effects + Quantum Electrodynamics).

    The Electromagnetic Force is what binds the electrons and the nuclei together. Since e-m is not only Coulomb, this determine that the most favored state is not the electron collapsing into the nucleus, but packed orbits around it. If you kick the electron strong enough it can leave the atom and leave behind an ionized atom, or even just the nucleus. Strongly (and totally) ionized atoms are strictly not "atoms" anymore and toghether with other form a compound called "plasma"

    Strong Force is what keeps the nucleus together. The nucleus can change by strong force by emitting or absorbing other protons/neutrons, also in the form of nuclei (and alpha particle, which is a nucleus of Helium-4).

    Weak Force is what define the numbers of neutrons and protons in the nucleus. It can happen that another balance between proton and neutron is more stable than the one currently present in the nucleus. In that case the nucleus decay by what is called a "Beta Decay", transforming a neutron into a proton and emitting an electron and a neutrino or vice-versa.

    An atom cannot, in what we call "standard model", chease to exist.
    But by the means of the three forces explained above and the reaction that them can trigger an atom can change shape and form, becoming something else like a plasma or a neutron superfluid or even quark matter in a neutron star.

    Thar just one notable exception, that's when gravity start to kick in for the atom and we have no idea what it happens in detail to it, and is when the atom falls into a black hole.
  11. Dec 5, 2013 #10


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    Here is a more basic reply than most in this thread. Apologies if it's too basic.
    You seem to be trying to apply a simple 'orbit under gravity' model here. In that model, there is no "force" pushing the orbiting object around. The only necessary force is always directed to the centre (for a simple, circular orbit) and no energy is needed to keep it going round and round. Newton says it will just keep on for ever and never 'wear out'. The idea of needing a force to keep things going was pre-Newtonian and made sense when everything on Earth needed energy input to keep it going because friction is normally such a massive factor in mechanics on Earth (it certainly used to be!).
    In the case of electrons in atoms, no force is necessary either and there is no loss mechanism so the electron can stay in its state for ever. The first 'orbiting' theories about electrons predicted that the electron would keep radiating EM energy and that it orbit should decay but Quantum Theory took care of that by saying that the orbit would need to decay (old fashioned terms) in steps (quanta) so energy couldn't just leak away in dribs and drabs.
  12. Dec 5, 2013 #11
    Atoms interact constantly with each other. So that can be seen as some kind of "friction"
    that disturbs the atoms.
    So where does come the energy, that compensates this disturbances and keeps the atoms going?
  13. Dec 5, 2013 #12


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    When you say "keeps the atoms going", what do you mean? An atom or molecule, on its own and in the ground state, will not change at all.
    There is no internal 'friction'. There is constant exchange of energy in the form of photons (and phonons) between molecules and the tendency is towards equilibrium, of course.
  14. Dec 5, 2013 #13


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    There's a difference between atoms interacting with each other, and the internal components of an atom maintaining their states. Thermal energy can cause atoms to jiggle around and interact, and if you removed this energy you could put the object at absolute zero and the atoms would be in their ground states. (Classically they wouldn't be jiggling around any more)

    However, electrons in their orbitals around a nucleus are not orbiting like planets orbit stars. There is no friction. A proper understanding would require some looking into Quantum Mechanics.

    If you'd like, start at the link below. There are also plenty of introductory books and articles online and in bookstores.
  15. Dec 5, 2013 #14
    By friction, I ment external forces.
    When there is electromagnetic interaction, electron's spin and orbital magnetic moments doesn't change. So there has to be something, that compensate the external influence and keeps them constant.



    and about quantum mechanics...:approve:

    Last edited: Dec 5, 2013
  16. Dec 5, 2013 #15


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    Why? If there is no interaction (because QM says there needn't be), why should there be anything to "compensate" for? If it is in its ground state it can go to a higher state by interaction or by absorbing a passing photon, if it is in a higher state then it can lose energy by interacting or by emitting a photon spontaneously. What else did you have in mind? An external influence will only have an effect if the energy gap is appropriate.
  17. Dec 5, 2013 #16
    Because there is interaction!
    If you have 2 magnets, they will attract or reppel each other.
    They interact with each other, right?
  18. Dec 5, 2013 #17


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    Two magnets are not exchanging energy when they are just sitting there, repelling or attracting each other. The 'interaction' (which implies some energy transfer) took place when they were moved together or the electric supply was turned on. By the definition of interaction, you are wrong.
  19. Dec 5, 2013 #18


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    It sounds like you are asking, "Why doesn't the electron spiral into the nucleus?". There's zero point energy in the electrons. As the electrons drop in energy levels, they are located closer to the nucleus on average. But the Heisenberg uncertainty principle puts some limit on how tightly they can be confined around the nucleus. In order to be tightly localized in space, the uncertainty in momentum must be very large. This is not possible for a bound electron. So, there must be a minimum possible energy for the electron.

    Another way of thinking about it, is that the electrons occupy orbitals in the atom. The higher energy states have orbital shapes with a greater number of nodes (places where the electron probability goes to zero). Think of a vibrating string. A greater number of nodes in the string indicates a higher energy vibration. But you cannot go less than 0 nodes. This is the minimum energy state, and you can't go any lower.

    There's no way to understand it classically. It's a quantum thing, and that's how it is.
  20. Dec 6, 2013 #19
    OK, then move one of them. What keeps spin and orbital magnetic moments in the other magnet constant?
  21. Dec 6, 2013 #20
    Earth doesn't fall on the Sun either. But if you slow it it will change it's orbit.
    If you accelerate it it can fly away.
    Planetary orbits are quantized too


    I speak for energy disturbances, that are not enough to change electrons orbital.
    Some say, that if external influence is not enough to change orbital, there is no interaction.
    If it is so, I can apply billions of Joules to a group of atoms, large enough, so external disturbance is not enough to change orbitals. If there is no interaction, this billion Joules just will disappear, and will have no effect on this group of atoms!
    Does this realy happens?
  22. Dec 6, 2013 #21
    Malverin, what is it you are asking about?

    Or are you trying to prove something?

    What is it, really?
  23. Dec 6, 2013 #22


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    Planetary orbits are NOT quantized. It is possible to put an object into any orbit around a star. All you need to do is accelerate it correctly. Electron orbitals ARE quantized. You cannot put an electron into any arbitrary orbital.

    If you spent energy, you did work. That energy was transferred from one system to the other. It did not disappear.
  24. Dec 6, 2013 #23
    Yes. That is the point.
    Energy can not disappear.
    So let we have an atom and we shoot it with 2 photons (from opposite directions to minimize atom movement), wich energy is not enough to change the orbitals.
    So what will happen with the energy?

    And for planetary orbits.

    Why not orbits described by this law to be the ones, that are stable. And any other orbit to be unstable an with time to change to these stable orbits (do electrons change their orbitals instantaneously?).
    Time and space scales in a planetary systems are big enough, and I don't think that we can be 100% sure that in time all orbits don't change to these stable predicted orbits.

    Some planets where discovered due to predictions of this law.
  25. Dec 6, 2013 #24


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    Either the photons are not absorbed, or the atom absorbs the energy in some other way than changing the energy levels of the electrons. For example, an atom can absorb a photon and be accelerated in a particular direction.

    That's not what quantization means. Take a star with a single planet. The planet can have absolutely any orbit. There are no restrictions. If you add more bodies to the system it becomes more complicated, and some orbits will become unstable, but they still exist as possible orbits. This is NOT true when it comes to quantized orbitals in atoms and molecules. An electron in a hydrogen atom can only occupy certain discrete energy levels, which correspond to certain orbitals. But it cannot occupy an energy level in between these discrete levels. It's not that the orbitals are unstable, it's that it isn't even possible for the electron to occupy them. They don't exist.
  26. Dec 6, 2013 #25
    When they are not absorbed, they bounce back or...?

    What is that other way of absorbtion?

    The photons are shot from opposite directions, so they can not move the atom.

    About electron orbitals, I can not prove now that electrons can be in transitions state (in neither lower or higher orbital) for some time, so it is better to accept your words and don't discuss this for now.
    Last edited: Dec 6, 2013
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