 D2h point group

A molecular point group containing identity, three mutually perpendicular twofold rotations, inversion, and three mirror reflections. In the conventional axis labelling, $z\sim B_{1u}$, $y\sim B_{2u}$ and $x\sim B_{3u}$; $yz\sim B_{3g}$ and $xz\sim B_{2g}$. The symmetry of a perpendicular atomic $p$ orbital includes its sign reversal when an operation reverses its axis, in addition to any permutation of atomic centres.