Assertion: radon's isotope | /r/HasAspect | long half-life
Facets:
value: very long
type: DEGREE
value: very
type: DEGREE
Source sentences:
text: Uranium has been present since the earth was formed and its most common isotope has a very long half-life (4.5 billion years), which is the time required for one-half of uranium to break down.
text: Their naturally occurring isotopes have very long half-lives, on the order of billions of years.