Q 3. Assign the oxidation number of the underline species in the following compounds or ions.

$\left(v\right) \underline{B}i{O}_3^{-}$

Dear Student,

Consider the oxidation number of Bi is 'x'.
We know the oxidation number of O is -2. And there is a negative charge on the ion.
Then,

x + 3(-2) = -1
x - 6 = -1
x = +5

Regards