Yes, HALON is a Scrabble word!

Letter values in Scrabble US: H 4, A 1, L 1, O 1, N 1.

Is it a valid word?

HALON is a valid word in the official Scrabble dictionary (US) and the UK Scrabble Dictionary, but not in Words with Friends (ENABLE).

a compound in which the hydrogen atoms of a hydrocarbon have been replaced by bromine and other halogen atoms; very stable; used in fire extinguishers although it is thought to release bromine that depletes the ozone layer