Assertion: thorium | /r/HasProperty | exposed to air
Facets:
Source sentences:
text: Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately hard, malleable, and has a high melting point.
text: Thorium is a silvery-white metal, which tarnishes when exposed to the air.
text: Thorium is a bright silvery metal and corrodes to black when exposed to air.
text: It is quite reactive and can ignite spontaneously if exposed to air when in finely divided form and forms thorium dioxide.