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Helium consists of 2 protons, 2 neutrons, and 2 electrons

  1. Mar 1, 2010 #1

    FeDeX_LaTeX

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    An element of helium consists of 2 protons, 2 neutrons, and 2 electrons.

    I have been told that anti-helium can exist if instead of 2 protons there are 2 antiprotons, instead of 2 neutrons there are 2 antineutrons, and instead of the 2 electrons there are 2 positrons. Is this true?

    Also, will the "anti-helium" exhibit different properties? Can we apply all of our laws of atomic physics to anti-matter as we do with normal matter?

    Thanks.
     
  2. jcsd
  3. Mar 1, 2010 #2
    Re: Anti-elements

    Yes, anti-helium would have two anti-protons, two anti-neutrons, and two positrons. It would have the same properties as helium (in anti-matter), and obey the same laws of atomic physics. One of the most convincing signatures of anti-matter in the universe would be detecting anti-alpha-particle (anti-helium nuclei) cosmic rays above the atmosphere.

    Bob S
     
  4. Mar 1, 2010 #3

    DaveC426913

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    Re: Anti-elements

    Yes, that's simply anti-matter.

    "Simply" should be quoted though, because it's rare to find atomic antimatter - not sure if it occurs in nature.

    To elaborate:

    Anti-helium would in principle behave the same as helium - if it were in an antimatter environment. For example, if it were surrounded by anti-nitrogen and anti-oxygen, it would be bouyant.

    If it were not in an anti-matter environment, it would annihilate.
     
  5. Mar 1, 2010 #4

    FeDeX_LaTeX

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    Re: Anti-elements

    Thanks for clearing that up guys.

    So is it true that, for every normal matter there exists a corresponding anti-matter? Where can anti-matter usually be found?
     
  6. Mar 1, 2010 #5

    DaveC426913

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    Re: Anti-elements

    It is more accurate to say: for every normal particle of matter there can exist a corresponding particle of antimatter.

    Note that even this is loose. Photons are their own antiparticles. (They're not matter, but they can be considered particles.)


    It's not found in any quantity or for a significant duration to be much use. And even then, we're talking subatmouic particles here, not atoms.

    Wiki:
    http://en.wikipedia.org/wiki/Antimatter#Origin_and_asymmetry
     
  7. Mar 1, 2010 #6
    Re: Anti-elements

    Indeed, antimatter is a very very rare occurrence in our universe. Most of it undergoes annihilation with matter once it is formed. If significant amounts of anti-matter exist...we wouldn't be here in the first place!

    This problem of matter-antimatter asymmetry (missing antimatter, if you would have it) is a big one in cosmology. A slight excess of matter over antimatter during the Big Bang is the reason why planets and whatnot, including us, exist today. Otherwise, our universe would just comprise loads of photons if antimatter and matter were present in equal amounts.
     
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