<Tr> <Td> Acetate </Td> <Td> CH 3COO − </Td> <Td> ethanoate </Td> </Tr> <Tr> <Td> Formate </Td> <Td> HCOO − </Td> <Td> methanoate </Td> </Tr> <Tr> <Td> Oxalate </Td> <Td> 2O2 − </Td> <Td> ethanedioate </Td> </Tr> <Tr> <Td> Cyanide </Td> <Td> CN </Td> <Td> </Td> </Tr>

What is the charge of the common ion formed by oxygen