Yes, WEEKEND is a Scrabble word!

Letter values in Scrabble US: W 4, E 1, E 1, K 5, E 1, N 1, D 2.

Is it a valid word?

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

a time period usually extending from Friday night through Sunday; more loosely defined as any period of successive days including one and only one Sunday