Yes, carbon is a Scrabble word!

...and is worth 10 points in Scrabble, and 13 points in Words with Friends

carbon

Noun

1. An abundant nonmetallic tetravalent element occurring in three allotropic forms: amorphous carbon and graphite and diamond; occurs in all organic compounds

2. 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

3. A copy made with carbon paper