CO3= CO3=
Top view Side view

The carbonate anion has a sixfold rotary-inversion axis (which is less easy to spot than the threefold rotation axis). In addition, it has 4 mirror planes plus 3 twofold rotation axes perpendicular to the -6 axis. It is not a requirement for the anion (or molecule) to be flat for it to possess this point-group symmetry: the eclipsed form of ethane, C2H6, also has the same symmetry as this anion.

The point-group symmetry for this molecule is given the crystallographic symbol -6 2 m.

© Copyright 1997-2006.  Birkbeck College, University of London. Author(s): Jeremy Karl Cockcroft