carbon oxoanion
carbon oxoanion
A negative ion consisting solely of carbon and oxygen  atoms, and therefore having the general formula C<small><sub><em>x</em></sub></small>O<small><sub><em>y</em></sub></small><small><sup><em>n</em>−</small></sup> for some integers <em>x</em>, <em>y</em> and <em>n</em>.