The carbonate ion, CO₃²⁻, has three canonical forms…

A higher bond order gives a shorter, stronger bond. The bond order in a resonance hybrid is the average over its canonical forms. Dipole moment: $\mu = q \times d$, with $1\ \text{D} = 3.336 \times 10^{-30}$ C m. Percent ionic character $=$ measured dipole $\div$ dipole if fully ionic $\times 100$.