Yes, CONFIDENTIAL is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, N 1, F 4, I 1, D 2, E 1, N 1, T 1, I 1, A 1, L 1.

Is it a valid word?

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

entrusted with private information and the confidence of another
(of information) given in confidence or in secret
denoting confidence or intimacy
the level of official classification for documents next above restricted and below secret; available only to persons authorized to see documents so classified