Experimental measurements show that all three C–O bond lengths in the carbonate ion,
CHEMISTRY · Single correct · AP · Chemistry · Compound Structure and Properties · Compound Structure and Properties
Problem
Experimental measurements show that all three C–O bond lengths in the carbonate ion, CO32−, are identical and lie between the typical lengths of a C–O single bond and a C=O double bond. Which of the following best accounts for this observation?
(a) Because the carbonate ion is trigonal-planar, symmetry forces all three C–O bonds to be identical in length regardless of how the electrons are distributed.
(b) Resonance delocalizes the π electrons over the three C–O bonds, giving each bond an effective order between 1 and 2.
(c) The double bond "jumps" rapidly among the three oxygens; each bond is a double bond one-third of the time and a single bond the rest of the time, so the measured length is the time-average between the two.
(d) All three oxygens withdraw electron density equally from carbon, uniformly shortening the C–O σ bonds until each becomes intermediate between a single and a double bond in length.