The time needed for one-half of the nuclei in a given quantity of a radioisotope to decay and emit their radiation and form a different isotope is called _________________________.

Radioisotope

A radioactive isotope of an element, used in various fields such as medicine for diagnostics and treatment, in research, and in industry.

Nuclei

The central and most important part of an atom, containing protons and neutrons.

Decay

The process of decomposition of organic matter by microorganisms, leading to the release of nutrients back into the environment.