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VSEPR theory is used to predict the arrangement of electron pairs around central atoms in molecules, especially simple and symmetric molecules. A central atom is defined in this theory as an atom which is bonded to two or more other atoms, while a terminal atom is bonded to only one other atom.
In 1939, he originally proposed the correlation between molecular geometry and number of valence electron pairs (both shared and unshared pairs). [4] This concept was later developed into the VSEPR theory of molecular geometry.
In 1927, he proposed the inert pair effect which describes the stability of heavier p-block atoms in an oxidation state two less than the maximum. In 1940 his Bakerian lecture with Herbert Marcus Powell correlated molecular geometry with the number of valence electrons on a central atom. [ 7 ]
According to VSEPR theory, diethyl ether, methanol, water and oxygen difluoride should all have a bond angle of 109.5 o. [12] Using VSEPR theory, all these molecules should have the same bond angle because they have the same "bent" shape. [12] Yet, clearly the bond angles between all these molecules deviate from their ideal geometries in ...
In VSEPR theory the electron pairs on the oxygen atom in water form the vertices of a tetrahedron with the lone pairs on two of the four vertices. The H–O–H bond angle is 104.5°, less than the 109° predicted for a tetrahedral angle, and this can be explained by a repulsive interaction between the lone pairs. [2] [3] [4]
This geometry is almost always consistent with VSEPR theory, which usually explains non-collinearity of atoms with a presence of lone pairs. There are several variants of bending, where the most common is AX 2 E 2 where two covalent bonds and two lone pairs of the central atom (A) form a complete 8-electron shell.
A simple example of steric activity is that of SnCl 2, which is bent in accordance with VSEPR theory. Some examples where the lone pair appears to be inactive are bismuth(III) iodide, BiI 3, and the BiI 3− 6 anion. In both of these the central Bi atom is octahedrally coordinated with little or no distortion, in contravention to VSEPR theory. [8]
According to the VSEPR theory of molecular geometry, an axial position is more crowded because an axial atom has three neighboring equatorial atoms (on the same central atom) at a 90° bond angle, whereas an equatorial atom has only two neighboring axial atoms at a 90° bond angle. For molecules with five identical ligands, the axial bond ...