The axis of rotation is a geometric straight line on which rotationally symmetric motion is performed. The axis of rotation is a geometric straight line on which rotationally symmetric motion is performed. When a rotation action is applied to an image (or a molecule), the vertical distance between any point in the image and the rotation axis (line) is required to be always constant. Set the base rotation angle = 2 / n. Because the number of independent and unequal rotation actions in the 2 angle range is n, the axis corresponding to the basic rotation action L (2 / n) is called n-revolution Axis, denoted by n. The degree of symmetry of the n-fold rotation axis is n.
The axis of rotation is a geometric straight line on which rotationally symmetric motion is performed. When a rotation action is applied to an image (or a molecule), the vertical distance between any point in the image and the rotation axis (line) is required to be always constant. Let the base angle of rotation Because The number of independent and unequal rotation actions in the angle range is , Which will be the basic action with rotation The corresponding axis is called Re-rotate the axis . The order of symmetry of the heavy rotation axis is .
Like square, , Base corner . and so Means heavy
have Heavy rotation axis Symmetric conjugated molecules, must contain Identical repeating units, rotated through an axis of symmetry perpendicular to the molecular plane After the angle, the spatial position of the entire molecule coincides with before the rotation. Rotene is the simplest representative, with only one atom per repeating unit; Radial ene also has Symmetry, but each repeating unit consists of two atoms. In general, suppose each repeating unit by Atomic composition, Next to it Can be linked by one key. Each An atom must pass by After rotating, change to its adjacent Position of an atom. After rotation, a group of atoms whose positions are replaced with each other is called an equivalent atom.
Can be numbered for repeating units , on Atoms can also be numbered , Which specifies equivalent atomic groups Same Set of equivalent atoms by Atomic composition .
