Chemistry - Solid State Question with Solution | TestHub

In a hexagonal close-packed (hcp) structure, the atoms are arranged in an ABAB... pattern.

For any given atom in a particular layer, there are $6$ nearest neighbors in the same plane.

Additionally, there are $3$ nearest neighbors in the layer immediately above it and $3$ nearest neighbors in the layer immediately below it.

Total number of nearest neighbors = $6+3+3=12$.

Thus, the coordination number or the maximum number of nearest neighbors for a given lattice point in the hcp structure is $12$.

Answer: $12$