Yes, LENTIL is a Scrabble word!

Letter values in Scrabble US: L 1, E 1, N 1, T 1, I 1, L 1.

Is it a valid word?

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

round flat seed of the lentil plant used for food
the fruit or seed of a lentil plant
widely cultivated Eurasian annual herb grown for its edible flattened seeds that are cooked like peas and also ground into meal and for its leafy stalks that are used as fodder

Also: lentil plant, lens culinaris.