84-1 Symmetry Elements and Operations The term symmetry is derived from the Greek wordsymmetria which means measured together We require a precise method to describe how an object or molecule is symmetric 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chemistry Department of Fudan University Chapter IV Molecular Symmetry and Point Group 2021/8/21 6 The term symmetry is derived from the Greek word “symmetria” which means “measured together”. We require a precise method to describe how an object or molecule is symmetric. §4-1. Symmetry Elements and Operations
Symmetry Operation A symmetry operation is a movement of a body such that, after the movement has been carried out, every point of the body is coincident with an equivalent point (or perhaps the same point) of the body in its original orientation Symmetry Element A symmetry element is a geometrical entity such as a line, a plane, or a point, with respect to Which one or more symmetry operations may be carried out 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chemistry Department of Fudan University Chapter IV Molecular Symmetry and Point Group 2021/8/21 7 Symmetry Operation A symmetry operation is a movement of a body such that, after the movement has been carried out, every point of the body is coincident with an equivalent point (or perhaps the same point) of the body in its original orientation. Symmetry Element A symmetry element is a geometrical entity such as a line, a plane, or a point, with respect to which one or more symmetry operations may be carried out
8 4-1-1 Symmetry Elements and Operations Required in Specifying Molecular Symmetry 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chemistry Department of Fudan University Chapter IV Molecular Symmetry and Point Group 2021/8/21 8 §4-1-1. Symmetry Elements and Operations Required in Specifying Molecular Symmetry
1. The Identity Operation E No matter how asymmetrical a molecule is, it must have an identity operation, E The symbol‘E” comes from the German,“ eigen," meaning‘ the same 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chemistry Department of Fudan University Chapter IV Molecular Symmetry and Point Group 2021/8/21 9 1. The Identity Operation E Ê No matter how asymmetrical a molecule is, it must have an identity operation, E •The symbol “E” comes from the German, “eigen,” meaning “the same
Phydical Chemiatry I Chapter IV Molecular Symmetry and Poirmt Group 2. Proper Axes and Proper Rotations C An n-fold rotation is symbolized by the element Cn, and represents n-1 rotational operations about the axis 20218/21 Chemistry Departme nt of Fudan University
Physical ChemistryI Chemistry Department of Fudan University Chapter IV Molecular Symmetry and Point Group 2021/8/21 10 2. Proper Axes and Proper Rotations Cn An n-fold rotation is symbolized by the element Cn , and represents n–1 rotational operations about the axis. m Cn