Yes, CARBONS is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, R 1, B 3, O 1, N 1, S 1.

Is it a valid word?

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

an abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds
a thin paper coated on one side with a dark waxy substance (often containing carbon); used to transfer characters from the original to an under sheet of paper
a copy made with carbon paper

Also: c, atomic number 6, carbon paper, carbon copy.