3.61 Beta Decay
3.61 Beta Decay
- Explain how and why beta decay occurs.
- Contrast beta-minus and beta-plus decay.
- Show how to write a balanced nuclear equation for beta decay.
- Describe dangers of beta decay.
If you hear the worddecaywhile your dentist is checking your teeth, it’s probably bad news. But if you’re an
unstable atomic nucleus, decay is good news. When the nucleus of an atom decays, it becomes more stable.
Which Nuclei Decay
Atoms with unstable nuclei are radioactive. To become more stable, the nuclei undergo radioactive decay. In
radioactive decay, the nuclei emit energy and usually particles of matter as well. There are several types of
radioactive decay, including alpha, beta, and gamma decay. Energy is emitted in all three types of decay, but only
alpha and beta decay also emit particles.
What Is Beta Decay?
Beta decay occurs when an unstable nucleus emits a beta particle and energy. A beta particle is either an electron
or a positron. An electron is a negatively charged particle, and a positron is a positively charged electron (or anti-
electron). When the beta particle is an electron, the decay is called beta-minus decay. When the beta particle is
a positron, the decay is called beta-plus decay. Beta-minus decay occurs when a nucleus has too many neutrons
relative to protons, and beta-plus decay occurs when a nucleus has too few neutrons relative to protons.