tetraedrisch

Tetraedrisch is an adjective used to describe something related to or shaped like a tetrahedron. In chemistry and crystallography, it denotes a geometry in which a central atom is bonded to four other atoms or groups arranged at the corners of a regular tetrahedron, yielding an ideal bond angle of about 109.5 degrees.

The term arises from sp3 hybridization, where four orbitals point toward the corners of a tetrahedron, creating a four‑way coordination around the central atom. According to VSEPR theory, four substituents around a central atom typically adopt this tetrahedral electron-pair geometry, and when all four substituents are atoms (no lone pairs), the molecular geometry is tetrahedral.

Common tetrahedral species include methane (CH4), carbon tetrachloride (CCl4), and silicon tetrachloride (SiCl4). In coordination and solid‑state chemistry, many compounds exhibit tetrahedral coordination, such as ammonium (NH4+) and certain metal complexes like [ZnCl4]2−, where four ligands surround the central atom. In crystal structures, tetrahedral arrangements also occur in minerals with zinc blende or similar motifs.

Real molecules may deviate from the ideal 109.5-degree angle due to differences in substituent sizes, multiple bonds, or electronic effects. Distortions are common in real systems, and in some contexts the electron‑pair geometry remains tetrahedral even if the observed molecular shape differs (as in cases with lone pairs).

Beyond chemistry, tetrahedral geometry appears in mathematics and symmetry discussions under the Td point group, and it is a standard reference shape in various modeling contexts.