Assertion: radon | /r/HasProperty | rare
Facets:
value: in nature
type: LOCATION
value: very
type: DEGREE
Source sentences:
text: Radon is rare in nature because its isotopes are all short-lived and because its source, radium, is a scarce element.
text: Radon is rare in nature because its isotopes are so short-lived and because its main source radium is also quite rare, according to Encyclopaedia Britannica.
text: Radon is very rare and radioactive, so it is not likely that you will have enough of it to do interesting demonstrations.