Answer:
Sometimes 4
Explanations:
Oxyanion are polyatomic anions which involves one or more oxygen element with a non metal. Example of oxyanions are:
[tex]CO_2^-,\text{ }NO_2^-,SO_4^{2-}[/tex]
As you can see, they have negative charges of -1, -2 and -3. This shows that number of oxygen bound to the central atom can be 2, 3 and sometimes 4.
