Assertion: actinium's number | /r/HasProperty | known including acobr
Facets:
Source sentences:
text: Only a limited number of actinium compounds are known including AcF 3 , AcCl 3 , AcBr 3 , AcOF, AcOCl, AcOBr, Ac 2 S 3 , Ac 2 O 3 and AcPO 4 .