Yes, MOTIVES is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, T 1, I 1, V 4, E 1, S 1.

Is it a valid word?

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

the psychological feature that arouses an organism to action toward a desired goal; the reason for the action; that which gives purpose and direction to behavior
a theme that is repeated or elaborated in a piece of music
a design or figure that consists of recurring shapes or colors, as in architecture or decoration
a design or figure that consists of recurring shapes or colors, as in architecture or decoration
a theme that is repeated or elaborated in a piece of music
a unifying idea that is a recurrent element in literary or artistic work