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  2. Molecular geometry - Wikipedia

    en.wikipedia.org/wiki/Molecular_geometry

    Trigonal pyramidal: A trigonal pyramidal molecule has a pyramid-like shape with a triangular base. Unlike the linear and trigonal planar shapes but similar to the tetrahedral orientation, pyramidal shapes require three dimensions in order to fully separate the electrons.

  3. Crystal system - Wikipedia

    en.wikipedia.org/wiki/Crystal_system

    The diamond crystal structure belongs to the face-centered cubic lattice, with a repeated two-atom pattern.. In crystallography, a crystal system is a set of point groups (a group of geometric symmetries with at least one fixed point).

  4. Molecular symmetry - Wikipedia

    en.wikipedia.org/wiki/Molecular_symmetry

    Symmetry elements of formaldehyde. C 2 is a two-fold rotation axis. σ v and σ v ' are two non-equivalent reflection planes.. In chemistry, molecular symmetry describes the symmetry present in molecules and the classification of these molecules according to their symmetry.

  5. Seesaw molecular geometry - Wikipedia

    en.wikipedia.org/wiki/Seesaw_molecular_geometry

    An atom bonded to 5 other atoms (and no lone pairs) forms a trigonal bipyramid with two axial and three equatorial positions, but in the seesaw geometry one of the atoms is replaced by a lone pair of electrons, which is always in an equatorial position. This is true because the lone pair occupies more space near the central atom (A) than does a ...

  6. Hexagonal crystal family - Wikipedia

    en.wikipedia.org/wiki/Hexagonal_crystal_family

    In particular, there are crystals that have trigonal symmetry but belong to the hexagonal lattice (such as α-quartz). The hexagonal crystal family consists of the 12 point groups such that at least one of their space groups has the hexagonal lattice as underlying lattice, and is the union of the hexagonal crystal system and the trigonal ...

  7. Orthorhombic crystal system - Wikipedia

    en.wikipedia.org/wiki/Orthorhombic_crystal_system

    In crystallography, the orthorhombic crystal system is one of the 7 crystal systems.Orthorhombic lattices result from stretching a cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular prism with a rectangular base (a by b) and height (c), such that a, b, and c are distinct.

  8. Berry mechanism - Wikipedia

    en.wikipedia.org/wiki/Berry_mechanism

    Trigonal bipyramidal molecular shape ax = axial ligands (on unique axis) eq = equatorial ligand (in plane perpendicular to unique axis). The Berry mechanism, or Berry pseudorotation mechanism, is a type of vibration causing molecules of certain geometries to isomerize by exchanging the two axial ligands (see the figure) for two of the equatorial ones.

  9. Trigonal pyramidal molecular geometry - Wikipedia

    en.wikipedia.org/wiki/Trigonal_pyramidal...

    In chemistry, a trigonal pyramid is a molecular geometry with one atom at the apex and three atoms at the corners of a trigonal base, resembling a tetrahedron (not to be confused with the tetrahedral geometry). When all three atoms at the corners are identical, the molecule belongs to point group C 3v.