Final answer:
A simple cubic unit cell contains exactly one atom. This is calculated by counting one-eighth of each of the eight corner atoms that are shared among adjacent unit cells.
Step-by-step explanation:
There is exactly one atom in a simple cubic unit cell. This is because each corner atom in the unit cell is shared among eight unit cells. As a result, only one-eighth of each atom actually belongs to any one unit cell.
Since there are eight corners in a cube, and each corner contributes one-eighth of an atom, the total is 8 × ⅛ = 1 atom within a single unit cell of a simple cubic lattice.