Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Radioactive Hydrogen Decay
Name: Alek
Status: student
Grade: 6-8
Location: NC
Country: USA
Date: Winter 2011-2012

Question:
What would a radioactive isotope of hydrogen, if there are any, decay into?



Replies:
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), decays into 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)

Jim Swenson


Alek,

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


Alek,

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) Canisius College


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.

Ray Tedder


Alek,

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.

Brad Sieve


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".

Vince Calder


Click here to return to the Chemistry Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory