Answer
Simple cubic cells have the lowest density, face-centered cubic the highest.
Work Step by Step
Simple cubic cells have one atom on each vertex of a cube, and has the lowest density of atoms in one unit cell. Body-centered cubic cells have one atom positioned on each vertex and one entire atom in the very center. Face-centered cubic cells are considered the closest form of packing with one atom on each vertex and one flushed on each face, so they have the highest density.
