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The coordination geometry depends on the number, not the type, of ligands bonded to the metal centre as well as their locations. The number of atoms bonded is the coordination number. The geometrical pattern can be described as a polyhedron where the vertices of the polyhedron are the centres of the coordinating atoms in the ligands. [1]
For molecules and polyatomic ions the coordination number of an atom is determined by simply counting the other atoms to which it is bonded (by either single or multiple bonds). [1] For example, [Cr(NH 3 ) 2 Cl 2 Br 2 ] − has Cr 3+ as its central cation, which has a coordination number of 6 and is described as hexacoordinate .
For typical ionic solids, the cations are smaller than the anions, and each cation is surrounded by coordinated anions which form a polyhedron.The sum of the ionic radii determines the cation-anion distance, while the cation-anion radius ratio + / (or /) determines the coordination number (C.N.) of the cation, as well as the shape of the coordinated polyhedron of anions.
If more hydrogen atoms are present, they are placed in open face positions to even out the coordination number of the vertices. For the special case of transition metal clusters, ligands are added to the metal centers to give the metals reasonable coordination numbers, and if any hydrogen atoms are present they are placed in bridging positions ...
In this each metal atom is at the centre of a cube with 8 nearest neighbors, however the 6 atoms at the centres of the adjacent cubes are only approximately 15% further away so the coordination number can therefore be considered to be 14 when these are on one 4 fold axe structure becomes face-centred cubic (cubic close packed).
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Coordination number (CN) is the number of nearest neighbors of a central atom in the structure. [1] Each sphere in a cP lattice has coordination number 6, in a cI lattice 8, and in a cF lattice 12. Atomic packing factor (APF) is the fraction of volume that is occupied by atoms. The cP lattice has an APF of about 0.524, the cI lattice an APF of ...
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