The D2 point groupD2 carries 4 symmetry operations in 4 classes, around a principal axis of order 2. A character table of the group therefore has 4 columns and as many irreducible representations.It contains only proper rotations, so a molecule in it is chiral and optically active. No direction is left invariant, so a molecule in it has no permanent dipole.In Hermann-Mauguin notation it is 222, and it is one of the crystal classes of the orthorhombic system. A diffraction pattern from a crystal in it shows the Laue symmetry mmm.

Biphenyl (C12H10): The 44° twist kills every mirror, so gas-phase biphenyl is chiral.

The 4 conjugacy classes of D2, in the order a character table prints them.

Class

Operations in it

C2(z)

C2(y)

C2(x)

Molecular point groups with their operations and character tables, the 230 space groups with a cell builder, and the 17 wallpaper and 7 frieze groups drawn live. The tool needs JavaScript, and WebGL2 for the 3D views; these are the pages it offers: