Wednesday, 8 August 2012

Gerade and ungerade

The symmetry notation u and g are sometimes used when describing molecular orbitals. This refers to the operation of inversion, which requires starting at an arbitrary point in the orbital, traveling straight through the center, and then continuing outwards an equal distance from the center. The orbital is designated g (for gerade, even) if the phase is the same, and u (for ungerade, uneven) if the phase changes sign.

Symmetry symbols can be used as a way to distinguish different orbitals in MO diagrams:


  1. Shouldn't it be arbitrary point of the 'orbital' and not molecule? Thanks for the help!

  2. why do you took d ortibals in eg t2g

  3. Gerade=bonding ??ungerade=antibonding ??

  4. Gerade=bonding ??ungerade=antibonding ??

    1. No- gerade= bonding orbital in sigma and pz orbital. Whereas, in the 2py and 2px orbitals, the antibonding orbital is gerade! So gerade does not necessarily always equal 'bonding' , and ungerade does not necessarily= 'antibonding'. Gerade and ungerade refer to the parity of the bonding/antibonding orbital in question. (i.e whether it is in phase, or out of phase)

  5. how do you designate a 'sign' to an orbital, in order to determine whether the 'phase changes sign'?