Assertion: fermium's isotope | /r/HasProperty | known with mass numbers
Facets:
value: from 245
type: OTHER
Source sentences:
text: Sixteen isotopes of mendelevium are known, with mass numbers from 245 to 260; all are radioactive.
text: Twelve isotopes of nobelium are known, with mass numbers 250–260 and 262; all are radioactive.