Yes, REPRESENTATION is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, P 3, R 1, E 1, S 1, E 1, N 1, T 1, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

a presentation to the mind in the form of an idea or image
a creation that is a visual or tangible rendering of someone or something
the act of representing; standing in for someone or some group and speaking with authority in their behalf
the state of serving as an official and authorized delegate or agent
a body of legislators that serve in behalf of some constituency
a factual statement made by one party in order to induce another party to enter into a contract
a performance of a play
a statement of facts and reasons made in appealing or protesting
the right of being represented by delegates who have a voice in some legislative body
an activity that stands as an equivalent of something or results in an equivalent

Also: mental representation, internal representation, theatrical performance.