Yes, MALL is a Scrabble word!

Letter values in Scrabble US: M 3, A 1, L 1, L 1.

Is it a valid word?

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

a public area set aside as a pedestrian walk
mercantile establishment consisting of a carefully landscaped complex of shops representing leading merchandisers; usually includes restaurants and a convenient parking area; a modern version of the traditional marketplace

Also: shopping mall, shopping center, shopping centre.