highcoordinationnumber

High coordination number refers to the phenomenon observed in certain chemical compounds and materials where an atom is bonded to a significantly larger number of neighboring atoms than is typically expected. In crystal structures, coordination number often describes the number of nearest neighbors surrounding a central atom. While common coordination numbers in simple ionic and covalent compounds are often 4, 6, or 8, high coordination numbers can extend to 10, 12, or even higher.

This increased number of bonds is usually facilitated by factors such as the size of the central atom and the surrounding ligands, the electronic configuration of the atoms involved, and specific bonding arrangements. For instance, the "magic number" 12 is often observed in close-packed structures like face-centered cubic (FCC) and hexagonal close-packed (HCP), where spheres are arranged in the most efficient manner, maximizing the number of touching neighbors.

High coordination numbers are not limited to simple solids. They can be found in complex molecules, particularly in organometallic chemistry, where large central metal atoms can accommodate numerous ligands. The study of high coordination number compounds is important for understanding chemical bonding, predicting material properties, and designing new functional materials. The electronic and steric factors governing the formation and stability of these species are areas of active research.