Assertion: protactinium | /r/HasProperty | most abundant isotope
Facets:
Source sentences:
text: Protactinium is an actinide (Z=91; atomic mass 231.0359); it name derives from protos (Greek for first) and actinium, because it most abundant isotope (231Pa) is parental to 227Ac.
text: In 1938, they discovered that protactinium 233 could be produced by neutron irradiation of thorium 232, the most abundant isotope in naturally occurring thorium.