Yes, RHENIUM is a Scrabble word!

Letter values in Scrabble US: R 1, H 4, E 1, N 1, I 1, U 1, M 3.

Is it a valid word?

RHENIUM is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a rare heavy polyvalent metallic element that resembles manganese chemically and is used in some alloys; is obtained as a by-product in refining molybdenum

Also: atomic number 75.