One of the ways that the nucleus can make itself stable is to change a neutron to a proton. This is a complex process, but the final product is a stable nucleus and an extra electron that comes racing out of the nucleus with a really high energy. This high-energy electron gets a special name—it's called a beta particle. The nucleus also emits a very tiny sub atomic particle called an antineutrino.

When a substance undergoes beta radiation it gives off beta particles. A beta particle has a negative charge and such small mass we can assume it to be zero.

A beta particle can be written three ways:

Source: Beta Radiation, University of Michigan Student Chapter of the Health Physics Society

A beta particle is essentially an electron that is spontaneously emitted from the nucleus of an unstable atom. Here are some examples of beta emitters:

• hydrogen-3 (tritium) used for glow in the dark paints
• carbon-14, used in dating organic materials up to 60,000 years old
• phosphorus-32, used in DNA research
• potassium-40, which is naturally found in bananas (Bananas deliver a VERY low dose of beta particles. So don't worry about it the next time you have a nice serving of banana pudding.)

Beta particles are less massive than alpha particles. They have a charge of -1 (electron). They can also travel farther and through more substances than alpha particles. Some beta particles with high energies, like those emitted from P-32, can penetrate the skin. Others, such as those emitted from tritium (H-3) cannot penetrate the outer skin layer. Metal and plastic can stop beta particles.

Source: Penetrating distances, University of Michigan Student Chapter of the Health Physics Society

Many beta emitters can be dangerous if you inhale, ingest, or absorb them into the body (but a banana is still safe).

Watch beta decay occur for a collection of nuclei or for an individual nucleus.

Click to Run

Source: Beta Decay, PhET, University of Colorado at Boulder

Now answer the following questions.

1. How many neutrons do you start with in the H-3 isotope?
   
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   2
2. What element isotope do you end up with?
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   He-3
3. Why doesn't the atomic mass of the new isotope change?
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   Because in the process of initiating beta radiation, a neutron changes to a proton.
4. How many neutrons does the H-3 change into protons?
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   1
5. How many beta particles does the parent isotope emit?
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   1

You can also watch the carbon-14 isotope decay by clicking on the C-14 nucleus below the He-3 nucleus.