Carbon trioxide (CO3) is an unstable oxide of carbon (an oxocarbon). The possible isomers of carbon trioxide include ones with molecular symmetry point groups Cs, D3h, and C2v. The C2v state, consisting of a dioxirane, has been shown to be the ground state of the molecule. Carbon trioxide should not be confused with the stable carbonate ion (CO2−3). 2 CO3 → 2 CO2 + O2