Yes, XENON is a Scrabble word!

Letter values in Scrabble US: X 8, E 1, N 1, O 1, N 1.

Is it a valid word?

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

a colorless odorless inert gaseous element occurring in the earth's atmosphere in trace amounts

Also: atomic number 54.

Not playable in Scrabble US: XE.