Yes, PEROXIDE is a Scrabble word!

Letter values in Scrabble US: P 3, E 1, R 1, O 1, X 8, I 1, D 2, E 1.

Is it a valid word?

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

a viscous liquid with strong oxidizing properties; a powerful bleaching agent; also used (in aqueous solutions) as a mild disinfectant and (in strong concentrations) as an oxidant in rocket fuels
an inorganic compound containing the divalent ion -O-O-

Also: hydrogen peroxide.