Summary:
- When identical spheres are stacked, each successive layer fits into the small spaces where different spheres come together.
- Closest packing is the most efficient arrangement of spheres.
- Atoms of a metal crystal are arranged in similar patterns, called close-packed structures.
- Pure metals naturally adopt one of these three closest packing arrangements.
- The coordination number of each atom in the face-centered cubic structure is 12.
- The hexagonal close- packed (hcp) structure also has acoordination number of 12.