Assertion: berkelium's isotope | /r/CapableOf | occur as one isotope
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Source sentences:
text: These two, together with 7Li, as well as 11B, 15N, 209Bi, and the stable isotopes of C, and O, are the only nuclides with low enough thermal neutron capture cross sections aside from Beryllium and fluorine occur only as one isotope,Be andF respectively.