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Chapter 31

31.1 Nuclear Radioactivity

31.2 Radiation Detection and Detectors

31.3 Substructure of the Nucleus

31.4 Nuclear Decay and Conservation Laws

31.5 Half-Life and Activity

Main ideas

A uranium-rich mineral emits invisible, penetrating rays that can darken a photographic plate enclosed in an opaque envelope. Becquerel’s rays originate in the nuclei of the atoms and have other unique characteristics. The emission of these rays is called nuclear radioactivity or simply radioactivity. The rays themselves are called nuclear radiation. A nucleus that spontaneously destroys part of its mass to emit radiation is said to decay (a term also used to describe the emission of radiation by atoms in excited states). A substance or object that emits nuclear radiation is said to be radioactive.

There are three types of nuclear radiation:

• alpha (particles),
• beta (particles),
• gamma (rays).

Radiation detectors are based directly or indirectly upon the ionization created by radiation, as are the effects of radiation on living and inert materials.

Two particles, both called nucleons, are found inside nuclei. The two types of nucleons are protons and neutrons; they are very similar, except that the proton is positively charged while the neutron is neutral.

Some nuclides are stable, apparently living forever. Unstable nuclides decay (that is, they are radioactive), eventually producing a stable nuclide after many decays. We call the original nuclide the parent and its decay products the daughters.

Additional Resources

OpenStax High School Physics, chapter 31

Khan Academy, Writing Nuclear Equations