Contrast is a principle of art. When defining it, art experts refer to the arrangement of opposite elements (light vs. dark colors, rough vs. smooth textures, large vs. small shapes, etc.) in a piece so as to create visual interest, excitement and drama.
An element of art, space refers to distances or areas around, between or within components of a piece. Space can be positive (white or light) or negative (black or dark), openor closed, shallow or deep and two-dimensional or three-dimensional. Sometimes space isn't actually within a piece, but the illusion of it is.