In radioactivity, what is the term used to describe the stability or instability of a nucleus?

The term that describes the stability or instability of a nucleus in radioactivity is known as "radioactive nature." This concept refers to the inherent characteristics of a nucleus that dictate whether it will undergo radioactive decay. A nucleus that is unstable will emit radiation in an attempt to reach a more stable state, while a stable nucleus does not undergo such decay. Understanding the radioactive nature of isotopes is essential for predicting how they behave over time and their potential hazards.

In contrast, other terms relate to different aspects of radioactivity. "Equilibrium" typically refers to a balanced state, often in the context of a system where the rates of production and decay of radioactive materials are equal. "Half-life" is a measure of the time it takes for half the quantity of a radioactive substance to decay, providing a specific quantitative perspective rather than a qualitative one regarding stability. "Radiological assessment" refers to the process of determining the presence and levels of radiation or radioactive materials, which is more about measurement and evaluation rather than the description of nuclear stability itself.