Yes, SPIDER is a Scrabble word!

Letter values in Scrabble US: S 1, P 3, I 1, D 2, E 1, R 1.

Is it a valid word?

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

predatory arachnid with eight legs, two poison fangs, two feelers, and usually two silk-spinning organs at the back end of the body; they spin silk to make cocoons for eggs or traps for prey
a computer program that prowls the internet looking for publicly accessible resources that can be added to a database; the database can then be searched with a search engine
a skillet made of cast iron