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Valence shell electron pair repulsion (VSEPR) theory (/ ˈ v ɛ s p ər, v ə ˈ s ɛ p ər / VESP-ər, [1]: 410 və-SEP-ər [2]) is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. [3]
The point group symmetry involved is of type C 4v. The geometry is common for certain main group compounds that have a stereochemically -active lone pair , as described by VSEPR theory . Certain compounds crystallize in both the trigonal bipyramidal and the square pyramidal structures, notably [Ni(CN) 5 ] 3− .
84 heptominoes (coloured grey) have no symmetry. Their symmetry group consists only of the identity mapping. 9 heptominoes (coloured red) have an axis of reflection symmetry aligned with the gridlines. Their symmetry group has two elements, the identity and the reflection in a line parallel to the sides of the squares.
A skew apeirogon in two dimensions forms a zig-zag line in the plane. If the zig-zag is even and symmetrical, then the apeirogon is regular. Skew apeirogons can be constructed in any number of dimensions. In three dimensions, a regular skew apeirogon traces out a helical spiral and may be either left- or right-handed.
Major types of shapes that either constitute or define a volume. Figure Definitions Images Parallelepiped: A polyhedron with six faces , each of which is a parallelogram; A hexahedron with three pairs of parallel faces; A prism of which the base is a parallelogram; Rhombohedron: A parallelepiped where all edges are the same length
In geometry, a zonohedron is a convex polyhedron that is centrally symmetric, every face of which is a polygon that is centrally symmetric (a zonogon).Any zonohedron may equivalently be described as the Minkowski sum of a set of line segments in three-dimensional space, or as a three-dimensional projection of a hypercube.
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. They have central angles from 104° to 109.5°, where the latter is consistent with a simplistic theory which predicts the tetrahedral symmetry of four sp 3 hybridised ...
A regular polyhedron is identified by its Schläfli symbol of the form {n, m}, where n is the number of sides of each face and m the number of faces meeting at each vertex. There are 5 finite convex regular polyhedra (the Platonic solids ), and four regular star polyhedra (the Kepler–Poinsot polyhedra ), making nine regular polyhedra in all.