Assertion: oxygen | /r/PartOf | about 20 percent of the air
Facets:
value: in mass
type: OTHER
Source sentences:
text: In the regions ordinarily accessible to man, however—i.e., within a few kilometres of the surface of the Earth—oxygen is the most abundant element: in mass, it makes up about 20 percent of the air, about 46 percent of the solid crust of the Earth, and about 89 percent of the water.