Oxidation State Balance Check Calculator
Check that the oxidation states in a formula add up to the species’ overall charge — a quick validity test for up to three elements.
How it works
Σ (oxidation state × atom count) = overall charge · balanced when the sum equals the species charge
A core rule of oxidation states is that they must sum to the overall charge of the species: zero for a neutral compound, or the ion’s charge for a polyatomic ion. This tool multiplies each element’s oxidation state by how many of that atom appear, adds the contributions for up to three elements, and compares the total with the charge you enter. A non-zero discrepancy means at least one assigned oxidation state or atom count is wrong.
Worked example
Sulfate, SO₄²⁻: sulfur is +6 with one atom (+6) and oxygen is −2 with four atoms (−8). The sum is +6 − 8 = −2, which matches the ion’s −2 charge, so the assignment is balanced.
Frequently asked questions
What should the oxidation states sum to?
For a neutral compound they sum to zero; for a monatomic or polyatomic ion they sum to the ion’s charge. That conservation rule is exactly what this calculator verifies.
How do I use it to find an unknown state?
Enter the known elements and set the unknown element’s count with a trial oxidation state, then adjust that state until the discrepancy reads zero. The value that balances the equation is the unknown oxidation state.
Does it handle only three elements?
The three slots cover almost all simple formulas and common oxoanions. For a compound with more elements, combine atoms that share an oxidation state, or leave unused slots at a count of zero so they add nothing.
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This calculator is for educational purposes. Double-check important results before acting on them.