Yes, MAXWELL is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, X 8, W 4, E 1, L 1, L 1.

Is it a valid word?

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

a cgs unit of magnetic flux equal to the flux perpendicular to an area of 1 square centimeter in a magnetic field of 1 gauss
Scottish physicist whose equations unified electricity and magnetism and who recognized the electromagnetic nature of light (1831-1879)

Also: j. c. maxwell, james clerk maxwell.

Not playable in Scrabble US: MX.