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Why does the normal hydrogen atom lack a neutron

  1. Jul 2, 2012 #1
    why is hydrogen the only element in the periodic table that lacks a neutron?
  2. jcsd
  3. Jul 2, 2012 #2


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    Staff: Mentor

    Two or more protons without any neutrons are not stable - their electrostatic repulsion is larger than the nuclear force. With an additional neutron, the nuclear force is stronger (and the electromagnetic force a bit weaker), and 3He is stable.
  4. Jul 2, 2012 #3


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    Right after the big bang the only nucleons were free protons and neutrons (which decay into protons). Nuclear fusion started to take place resulting in a lot of helium nuclei plus a small amount of other light nuclei, deuterons and Lithium nuclei. The net result was that the universe (after cooling down enough to form atoms) was about 75% H1 and 25% He4 and trace amounts of the others. The rest of the elements got created in stars and supernovae. However most of the universe is still H1 and He4.
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