Yes, SODIUM is a Scrabble word!

Letter values in Scrabble US: S 1, O 1, D 2, I 1, U 1, M 3.

Is it a valid word?

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

a silvery soft waxy metallic element of the alkali metal group; occurs abundantly in natural compounds (especially in salt water); burns with a yellow flame and reacts violently in water; occurs in sea water and in the mineral halite (rock salt)

Also: atomic number 11.