Octahedral molecular geometry

Octahedral molecular geometry has a central atom bonded to six surrounding atoms arranged at the vertices of an octahedron. Its ideal bond angles are 90° and 180°.

Valence shell electron pair repulsion theory: A model that predicts molecular shapes by treating electron domains around a central atom as mutually repulsive. It gives a basic geometric account of six bonding domains spreading around a central atom.
Octahedral coordination complex: A coordination complex in which a central atom has six ligands arranged approximately at the vertices of an octahedron. It is the most common chemical setting for octahedral molecular geometry.
Hexaamminecobalt(III) chloride: A cobalt(III) salt containing the octahedral complex ion [Co(NH₃)₆]³⁺ and chloride counterions. Its six equivalent ammonia ligands provide a classic octahedral example.
Tetrahedral molecular geometry: A molecular shape with four surrounding atoms at the vertices of a tetrahedron. Four-coordinate tetrahedral molecules differ from six-coordinate octahedral ones in angles and ligand count.
Coordination number: The number of atoms or groups directly bonded to a central atom in a coordination entity. Octahedral complexes have six directly attached ligands.
Crystal field theory: A model of transition-metal complexes that treats ligands as electrostatic fields splitting metal d-orbital energies. The octahedral ligand arrangement splits the five d orbitals into two energy groups.
Hexafluorosilicate: The anion [SiF₆]²⁻, in which silicon is surrounded by six fluorine atoms. Its six identical Si–F bonds give a nearly ideal octahedral molecular shape.
Square planar molecular geometry: A molecular shape with four surrounding atoms in one plane at the corners of a square. Square-planar complexes are four-coordinate and flat, unlike octahedral six-coordinate structures.
Ligand: An atom, ion, or molecule that donates electron density to a central atom to form a coordination bond. The six surrounding groups in many octahedral complexes are ligands.
Ligand field theory: A molecular-orbital treatment of bonding and orbital energies in transition-metal complexes. It explains how metal–ligand bonding and orbital occupancy influence octahedral structures.

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