Yes, CARELESS is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, R 1, E 1, L 1, E 1, S 1, S 1.

Is it a valid word?

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

marked by lack of attention or consideration or forethought or thoroughness; not careful
effortless and unstudied
(usually followed by `of') without due thought or consideration