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Electron's Mass

  1. Nov 23, 2014 #1
    It's my understanding that there is a clearly defined electron rest mass. In atoms, electrons in higher energy levels have a larger amount of energy than electrons in lower energy levels. I think e=mc^2 shows mass-energy equivalence. So seeing all of this, I thought that electrons' masses in different levels must be different. Is this true?
    I've also read that the electron's mass cannot change, or else the universe would be completely different, if not completely disappear. So my question is, can an electron's mass change?
  2. jcsd
  3. Nov 23, 2014 #2


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    According to the modern acceptance of the term <mass>, there's only one type: rest/invariant mass. The adjective <invariant> tells pretty much all there is to say. For outdated usage of the term <mass>, see the FAQ: https://www.physicsforums.com/threads/what-is-relativistic-mass-and-why-is-it-not-used-much.783220/ [Broken]
    Last edited by a moderator: May 7, 2017
  4. Nov 23, 2014 #3


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    The mass of the whole system (electron+nucleus) depends on the energy level of the electron.
    The mass of the electron is always the individual particle and constant.
  5. Nov 23, 2014 #4


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    In general, the mass of a composite system (e.g. an atom) does not equal the sum of the masses of its individual components. For example, the mass of a hydrogen atom equals the mass of the proton plus the mass of the electron minus the mass-equivalent of the binding energy of the system.
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