biology and chemistry
type: Concept
narrower: radioactivity

physical processes
type: Concept
narrower: radioactivity

radioactivity
type: Concept
definition: Radioactivity is the process by which chemical elements decay from unstable to stable states by emitting sub-atomic particles and/or energy from molecules over a period of time ranging from infinitesimal fractions of a second to thousands of millions of years. Many elements exist in different isotopes, which are variant forms of molecular structure within elements of the same number and position on the periodic table of elements. [Source: Encyclopedia of Environment and Society; Radioactivity]
broader: physical processes
broader: biology and chemistry

concepts
type: Collection
type: ConceptGroup
member: radioactivity