Final answer:
In a body-centered cubic unit cell of a metal, there are two atoms; one atom contributed by the eight corners when combined (each corner contributing one-eighth of an atom), and one atom from the center.
Step-by-step explanation:
The student asked how many atoms are in one body-centered cubic unit cell of a metal. In a body-centered cubic (BCC) structure, metal atoms occupy the eight corners of a cube and one atom is located at the center of the cube. Each corner atom is shared among eight unit cells, so only one-eighth of each corner atom is actually within a given unit cell. Therefore, the eight corner atoms contribute a total of one atom (8 × 1/8 = 1), and the centered atom contributes one whole atom since it is completely within the unit cell. Adding these contributions together, we conclude that a body-centered cubic unit cell contains two atoms.