Enter a chemical formula to determine the oxidation state of each element.
Type a chemical formula using standard notation (e.g., KMnO4, H2SO4, Na2Cr2O7). For polyatomic ions, set the overall charge (e.g., CrO4 with charge −2 for chromate). The calculator applies standard oxidation state rules to determine each element's oxidation number.
Oxidation states are assigned using a hierarchy of rules: (1) Free elements have oxidation state 0. (2) Monatomic ions equal their charge. (3) Fluorine is always −1. (4) Oxygen is usually −2 (except in peroxides: −1, and OF₂: +2). (5) Hydrogen is usually +1 (except in metal hydrides: −1). (6) Group 1 metals are +1, Group 2 are +2. (7) The sum of all oxidation states equals the overall charge of the species.
For compounds with one unknown oxidation state (most cases), the calculator solves algebraically: assign known states to all elements with fixed rules, then solve for the remaining element. This handles transition metals, main-group elements in unusual states, and complex oxoanions.
Worked example: In KMnO₄: K = +1 (Group 1), O = −2 (standard). Sum must equal 0 (neutral compound). So: +1 + Mn + 4(−2) = 0 → Mn = +7.