Yes, IDENTITY is a Scrabble word!

Letter values in Scrabble US: I 1, D 2, E 1, N 1, T 1, I 1, T 1, Y 4.

Is it a valid word?

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

the distinct personality of an individual regarded as a persisting entity
the individual characteristics by which a thing or person is recognized or known
an operator that leaves unchanged the element on which it operates
exact sameness

Also: personal identity, identity element, identity operator, indistinguishability.