Yes, HYDROGEN is a Scrabble word!

Letter values in Scrabble US: H 4, Y 4, D 2, R 1, O 1, G 2, E 1, N 1.

Is it a valid word?

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

a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas; the simplest and lightest and most abundant element in the universe

Also: h, atomic number 1.