Answer:
CN⁻
Step-by-step explanation:
Oxyanion:
Oxyanion is the anion that have oxygen atom.
General formula:
The general formula for oxyanion is AₓOₓ⁻².
A = symbol of element combining with oxygen.
O = oxygen atom
z,x, = integers
a) = NO⁻
Its is an oxyanion because oxygen atom is present with nitrogen.
b) = SO₄⁻
It is an oxyanion because oxygen atom is present.
c) = CN⁻
This is not an oxyanion because there is no oxygen atom present.
d= CO₃²⁻
It is also an oxyanion because of presence of oxygen atom.