# Ion naming confusion with the bi prefix

1. Feb 19, 2012

### Bipolarity

Ion naming confusion with the "bi" prefix

I am little confused on when you use the "bi" prefix to denote the existence of a proton in front of an oxyanion.

For example, I know that $$[HCO_{3}]^{-}$$ is called bicarbonate as well as hydrogen carbonate.

A problem arises when I try to define the various protonated versions of the phosphate and arsenate ions.

$$PO_{4}^{3-}$$ is phosphate...
$$[HPO_{4}]^{2-}$$ is hydrogen phosphate if I am not wrong...
$$[H_{2}PO_{4}]^{-}$$ is dihydrogen phosphate if I am not wrong...

But which of the above three would be referred to as the "biphosphate" ion??

I assume an analagous situation works for the arsenate ion? $$AsO_{4}^{3-}$$

2. Feb 19, 2012

### Staff: Mentor

Re: Ion naming confusion with the "bi" prefix

"Bi"is outdated, as far as I know it was used for diprotic acids salts whenever they were neutralized only halfway (so it won't make sense for phosphates). But I can be wrong.