Yes, RHODIUM is a Scrabble word!

Letter values in Scrabble US: R 1, H 4, O 1, D 2, I 1, U 1, M 3.

Is it a valid word?

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

a white hard metallic element that is one of the platinum group and is found in platinum ores; used in alloys with platinum

Also: atomic number 45.

Not playable in Scrabble US: RH.