kiseloxygentetraedrat

Kiseloxygentetraedrat, or the silicon–oxygen tetrahedron, is the fundamental structural unit of silicate minerals. It consists of a central silicon atom in the +4 oxidation state surrounded by four oxygen atoms at the corners of a tetrahedron. In an ideal unit, each Si–O bond length is about 1.60 Å, and the internal O–Si–O angles are close to the tetrahedral value. In crystalline silicates, these tetrahedra commonly link by sharing oxygen atoms with neighboring tetrahedra, forming a wide range of three‑dimensional networks.

Connectivity and classification are based on how tetrahedra link through shared oxygens. When they share no oxygens, the units are isolated (nesosilicates, e.g., olivine). When they share one oxygen, they form single chains (inosilicates, e.g., pyroxenes); sharing two oxygens yields double chains (amphiboles); sharing three oxygens creates two‑dimensional sheets (phyllosilicates, e.g., micas and clays); sharing all four oxygens builds a three‑dimensional framework (tectosilicates, e.g., quartz and feldspars). The degree of polymerization is often described using the Q^n designation, where n indicates the number of bridging oxygens per silicon.

Silicate minerals with silicon–oxygen tetrahedra are the most abundant on Earth and form the basis of rocks such as granite, basalt, and sandstone. The arrangement and connectivity of the tetrahedra influence properties like hardness, melting behavior, and crystal structure. Beyond geology, silicate tetrahedra are central to glassmaking, ceramics, and many industrial materials.