Radioactive Hydrogen Decay
Date: Winter 2011-2012
What would a radioactive isotope of hydrogen, if there are any, decay into?
Hydrogen-3 (1 proton, 2 neutrons) decays by beta-decay into helium-3 (2 protons, 1 neutron).
Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming
Hydrogen 3 "Tritium", (1 proton + 2 neutrons),
Helium 3, (2 protons + 1 neutron),
by emitting a fast electron called a Beta particle.
It is a fairly general tendency that nuclei with too many neutrons undergo beta decay,
getting fewer neutrons and more protons, so then they are more stable.
And nuclei with not enough neutrons undergo alpha decay
(coughing out a whole 2p2n Helium nucleus),
which also tends to correct the neutron/proton balance, because
elements with fewer protons need a lower neutron/proton ratio to be stable.
The ratio at which stable balance occurs varies gradually over atomic number,
as low as 0 : 1 for Hydrogen 1,
to 1 : 1 for light elements like Carbon,
to 1.6 : 1 for Uranium and such.
Whatever decay happens will move the starting nucleus towards a more central balance of protons and neutrons.
It is usually the whole point of doing a decay.
There are other decays such as positron emission, electron capture, and spontaneous fission.
They too tend to happen only when they move the nucleus towards balanced neutron#/proton#.
I think fission does it by throwing out a bare neutron or two along with the splitting into daughter elements.
Two other reasons to decay:
1) the nucleus is just too big
and even the best ratio is no longer stable
any more (Uranium and up)
They do fission and/or a whole string of alpha and beta decays.
2) this nucleus happens to be in an excited state, has extra energy locked inside,
so it decays to its resting state by emitting a gamma-ray photon,
which is pure energy with no charge, mass, or baryon-count.
(Cobalt 60m -> Cobalt 60, for example)
There are a number of isotopes of hydrogen. An isotope of an element
is an element of the same type (that is, the same number of protons)
with various masses (that is, a different number of neutrons).
All hydrogen isotopes have one proton.
Hydrogen with no neutrons, known as hydrogen, is stable and
therefore does not decay.
Hydrogen with one neutron, known as deuterium, is also stable and
therefore does not decay.
Hydrogen with two neutrons, known as tritium (and a common byproduct
of nuclear power) is unstable and decays by beta emission, so the
daughter product of tritium decay is helium.
Leslie Kanat, Ph.D.
Professor of Geology
Remember that there are three basic types of spontaneous decay for
unstable nuclei: alpha-, beta-, and gamma emissions. Since these are
spontaneous decay mechanisms, these must happen because the nucleus
is highly energetic, unstable and goes through the release of alpha,
beta or gamma particles and results in a less energetic, more stable nucleus.
We will not consider gamma radiation since this does not result in a
transformation of the nucleus, just a release of energy to result in
a less energetic form of the same nucleus.
Your confusion must come from the thought that it is not possible
for a tritium or deuterium nucleus to release an alpha particle
because there cannot be an alpha particle within a deuterium or
tritium nucleus - and you would be right. However, a beta emission
is possible. Consider that a release of a beta particle is
essentially the transformation of a neutron into a proton with a
concurrent release of an electron from the nucleus. So tritium,
having two neutrons and one proton, becomes a nucleus having one
neutron and two protons, with a release of a beta particle (the
electron from the nucleus). I'm sure you can figure out what this
new nucleus is called.
Greg (Roberto Gregorius)
Hydrogen-3, more commonly called tritium, contains one proton and
two neutrons in its nucleus. It is radioactive with a half life
about 12 years. It decays through what is called beta decay,
decaying into helium-3. In beta decay a beta particle (which is a
lot like an electron) is emitted from one of the 2 neutrons in the
nucleus, and that neutron becomes a proton.
There is one form of natural hydrogen that is radioactive (only form
I know of) and that is Tritium or Hydrogen-3. It is hydrogen with a
mass of three and one proton. During decay (undergoing beta decay)
it releases beta particles (an electron) and forms Helium-3.
Hydrogen has three major isotopes: (1H1) [normal hydrogen], (2H1)
[deuterium], and (3H1) [tritium = one proton and two neutrons]. In addition,
there are three heavier isotopes with masses 4,5, and 6 but their half-life
is of the order of 10^-23 seconds. Tritium has a half-life of 12.33 years
and decays by beta emission (an electron). The product of this decay is 4He2
(helium), that is, the atomic number increases by +1. You can find all the
details for all the elements if you search the site:
"table of the isotopes decay".
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Update: June 2012