Final answer:
The coordination number of a chromium atom in a body-centered cubic structure is 8, as it is surrounded by 8 other atoms at the corners of the cube.
Step-by-step explanation:
The coordination number of a chromium atom in the body-centered cubic (bcc) structure of chromium is 8. This is because in a body-centered cubic structure, each chromium atom is surrounded by 8 other chromium atoms: one on each corner of the cube with the atom in question positioned at the center of the cube.
This is in contrast to the coordination number of 12 in the face-centered cubic (fcc) and hexagonal close-packed (hcp) structures.