▁for ▁the ▁c oval ent ▁b onds ▁also ▁behave ▁as ▁if ▁they ▁were ▁del ocal ized . ▁These ▁phen omena ▁are ▁often ▁explained ▁as ▁a ▁reson ance ▁between ▁two ▁or ▁more ▁conventional ▁mole cular ▁structures ▁that ▁differ ▁on ▁the ▁location ▁of ▁those ▁charges ▁and ▁b onds . ▁ ▁The ▁carbon ate ▁ion , ▁for ▁example , ▁is ▁considered ▁to ▁have ▁an ▁" aver age " ▁of ▁three ▁different ▁structures : ▁▁▁▁ ▁so ▁that ▁each ▁o xygen ▁has ▁the ▁same ▁negative ▁charge ▁equivalent ▁to ▁ ▁of ▁an ▁electron , ▁and ▁each ▁C – O ▁bond ▁has ▁the ▁same ▁average ▁val ence ▁of ▁. ▁This ▁model ▁accounts ▁for ▁the ▁observed ▁three fold ▁symmetry ▁of ▁the ▁an ion . ▁ ▁Similarly , ▁in ▁a ▁de pro ton ated ▁car box yl ▁group ▁– , ▁each ▁o xygen ▁is ▁often ▁assumed ▁to ▁have ▁a ▁charge ▁of ▁− ▁and ▁each ▁C – O ▁bond ▁to ▁have ▁val ence ▁, ▁so ▁the ▁two ▁o xy gens ▁are ▁equivalent . ▁The ▁cro con ate ▁an ion ▁ ▁also ▁has ▁five fold ▁symmetry , ▁that ▁can ▁be ▁explained ▁as ▁the ▁super position ▁of ▁five ▁states ▁leading ▁to ▁a ▁charge ▁of ▁− ▁on ▁each ▁o xygen . ▁ ▁These ▁reson ances ▁are ▁believed ▁to ▁contribute ▁to ▁the ▁stability ▁of ▁the ▁an ions . ▁ ▁Rel ated ▁comp ounds ▁ ▁Ox oc ar bon ▁ac ids ▁An ▁ox oc ar bon ▁an ion ▁ ▁can ▁be ▁seen ▁as ▁the ▁result ▁of ▁removing ▁all ▁pro tons ▁from ▁a ▁corresponding ▁acid ▁C x H n