Final answer:
Chromium has a body-centered cubic (BCC) crystal structure with two atoms per unit cell and a coordination number of eight.
Step-by-step explanation:
The crystal structure of chromium is one in which it crystallizes with atoms arranged in a body-centered cubic (BCC) lattice structure. This structure features atoms at all of the corners of the cube and a single atom at the center. Each corner atom is an eighth part of an atom within the unit cell, contributing to one whole atom when considering all eight corners. Together with the atom at the center, the BCC unit cell thus contains two atoms in total.
Moreover, in BCC, chromium has a coordination number of eight, meaning that each chromium atom is surrounded by eight other chromium atoms. This geometry comes from four atoms touching the central atom from the layer above and four from the layer below. It is important to note that while BCC structures are common among some elements, others may crystallize in different structures, such as face-centered cubic (FCC) or hexagonal closest packed (HCP).