These oxygen atoms are at different places in space, so these are different structures. The angle between the hands stays the same, but because they point to different places in space, they indicate a different time. The position of the carbon-oxygen bond is like the fixed angle of the clock hands, but pointing to different places on the clock face. When more than one Lewis structure can be drawn, the molecule or ion is said to have resonance . The individual Lewis structures are termed contributing resonance structures .
Resonance is a common feature of many molecules and ions of interest in organic chemistry.
Measurement of structures B and C would give the same results as well. As it turns out, laboratory measurements show that all three bonds are equal and between single and double bond length. This suggests that none of the Lewis structures we have drawn are correct. It further suggests that the actual structure has three equal carbon-oxygen bonds that are intermediate between single and double bonds. Perhaps the three Lewis structures for carbonate ion are in rapid equilibrium.