Octahedral voids have 6 spheres but why do we call them Octahedral?

Octahedral voids, also known as octahedral holes or octahedral interstices, are spaces between atoms or molecules that are shaped like a regular octahedron. A regular octahedron is a polyhedron with eight faces, each of which is an equilateral triangle.

Octahedral voids are called "octahedral" because they have a shape that is similar to that of a regular octahedron. The term "octahedron" comes from the Greek words "octo," meaning "eight," and "edron," meaning "face." The prefix "octa-" refers to the number 8, which is the number of faces on a regular octahedron.

In the case of octahedral voids, the six spheres that fill the voids are arranged in a way that resembles the eight faces of a regular octahedron. The spheres are placed at the vertices of the octahedron, with one sphere at the center of the void and five spheres at the corners of a regular pentagon.

Overall, the term "octahedral voids" refers to the shape of the voids, which is similar to that of a regular octahedron, even though the voids are filled with six spheres rather than eight faces.

The Naming Of Octahedral Voids

Octahedral voids are named after the shape of an octahedron, which is a geometric solid with eight faces, twelve edges, and six vertices. The term "octahedral" comes from two Greek words, "octa" meaning eight and "hedron" meaning face or base. This name is somewhat misleading, as octahedral voids do not actually have eight faces or sides.

The historical origin of the term "octahedral" dates back to the early studies of crystal structures in the 19th century. At that time, scientists were discovering new crystal structures and attempting to describe them using geometric shapes. They observed that some crystals had voids or empty spaces within the crystal lattice and that these voids were often located at positions that corresponded to the vertices or edges of an octahedron.

Despite the presence of six spheres in an octahedral void, it is still called "octahedral" because of the relationship between the geometry of the void and the shape of an octahedron. Specifically, the six spheres surrounding an octahedral void are arranged in a way that corresponds to the six vertices of an octahedron. This arrangement gives the void its characteristic octahedral symmetry and makes it useful for understanding the overall structure of the crystal lattice.