Determine the oxidation state of each element in WO₄^2– ion.

Identify each of the oxidation numbers for each element in the balanced redox reaction below: 

2 CrO₂^-(aq) + 8 OH^-(aq)  +  3 S₂O₈^2-(aq) → 2 CrO₄^2-(aq) + 4 H₂O(aq) +  6 SO₄^2-(aq)

Determine which region in the periodic table where elements commonly have multiple positive oxidation states.

Calculate the oxidation number of bromine in each of the following ions:
a. BrO₄⁻
b. BrO₂⁻
c. BrO⁻
d. BrO₃⁻

What is the oxidation state of each element of the following compounds?

1) CH₂Cl₂

2) (NH₄)₂ CrO₄

3) CuCO₃

4) BaO

5) K₂Cr₂O₇