Скачать с ютуб Symmetry elements and operations в хорошем качестве

Symmetry elements and operations

A symmetry operation is an action of rotation or reflection or both that leaves an object in an orientation indistinguishable from the original one. A symmetry element is a line, a plane or a point in or through an object about which a symmetry operation is performed. There are 5 different types of symmetry elements, Identity given by the symbol E, Proper axis or Rotational axis of symmetry designated by Cn, Plane of symmetry or mirror plane designated by sigma, centre of symmetry or inversion centre given by i and improper axis or alternating axis of symmetry denoted by Sn. Different symmetry elements and their related operations have been discussed with appropriate examples.