Assertion: astatine | /r/HasProperty | second synthetic element
Facets:
Source sentences:
text: Astatine was the second synthetic element to be conclusively identified just three years after technetium, was isolated by Carlo Perrier and Emilio Segre of the University of Palermo.
text: Astatine was the second synthetic element to be conclusively identified, technetium having been discovered by Segrè and Carlo Perrier three years earlier.