Characterization of atoms by their nuclear properties, as the number of protons and the number of neutrons. The different nuclides of an element are its isotopes (equal proton number, but different neutron numbers). Isomers of this particular nuclide are equal in the proton and mass numbers, but differ in their energy content. Unstable nuclides which are radioactive are called radionuclides.

See also Isotope, Isomer and Decay.

(NAA) Neutron activation analysis is a very sensitive analytical technique to determine even very low concentration of chemical elements, trace elements for example, in small biological samples.
NAA becomes commercial available in the USA in 1960.
In the activation process stable nuclides in the sample, which is placed in a neutron beam (neutron flux, 90-95% are thermal neutron with low energy levels under 0.5 eV), will change to radioactive nuclides through neutron capture (artificial radioactivity). These radioactive nuclides decay by emitting alpha-, beta-particles and gamma-rays with a unique half-life. Qualitative and quantitative analysis of the sample is done with a high-resolution gamma-ray spectrometer.
NAA is subdivided into the following techniques:

Radionuclides are naturally occurring or artificially produced atoms with unstable nuclei. Therefore radionuclides undergo a radioactive decay, and emit gamma ray(s) and/or subatomic particles.
Radionuclides are used as agents in nuclear medicine and to destroy tumors in cancer therapy.

See Isotope and Radioactive Decay.

Beta radiation consists of high energetic electrons or positrons emitted spontaneously from nuclei in decay of some radionuclides. Also called beta particle and sometimes shortened to beta (e.g., beta-emitting radionuclides). Beta radiation is used for example in cancer treatment.
The average reach of beta radiation in tissue is 3.5 mm.

See also Beta Decay.

Binding energy is equal to the amount of energy which is used to free electrons or disintegrate nuclides from their atomic bond.
The electron binding energy of a hydrogen atom is with 13.6 eV very low. The nuclear binding energy of an alpha-particle, energy equivalent of the sum of the individual masses of nuclides minus the mass of the whole nucleus, is 28.3 MeV.

See also Alpha Decay, Beta Decay and Gamma Quantum.