A proton is a subatomic particle with a positive electric charge and a mass of approximately 1 atomic mass unit (amu).

A neutron is a subatomic particle with no electric charge and a mass of approximately 1 atomic mass unit (amu).

The atomic number of an atom is the number of protons in its nucleus.

The mass number of an atom is the sum of the number of protons and neutrons in its nucleus.

Isotopes are atoms of the same element that have different numbers of neutrons.

Radioactive decay is the process by which an unstable nucleus releases energy and particles to become a more stable nucleus.

Alpha decay is the type of radioactive decay in which an unstable nucleus emits an alpha particle, which consists of two protons and two neutrons.

Beta decay is the type of radioactive decay in which an unstable nucleus emits a beta particle, which is an electron or a positron.

Gamma decay is the type of radioactive decay in which an unstable nucleus emits a gamma ray, which is a high-energy photon.

Neutron decay is the type of radioactive decay in which an unstable nucleus emits a neutron.

The strong nuclear force is the force that holds the protons and neutrons together in the nucleus of an atom.

Binding energy is the property of a nucleus that describes its resistance to being split apart.

Half-life is the property of a nucleus that describes the time it takes for half of the atoms in a sample to decay.

Radioactivity is the property of a nucleus that describes the amount of radioactivity it emits.

Isotopic abundance is the property of a nucleus that describes the relative abundance of its isotopes.