Oxidation Number Rules

Free elements: Oxidation number = 0 (e.g., Na, O₂, P₄).
Monatomic ions: Oxidation number = charge (e.g., Na⁺ = +1, Cl⁻ = −1).
Fluorine: Always −1 in compounds.
Oxygen: Usually −2 (except in peroxides = −1, OF₂ = +2).
Hydrogen: Usually +1 (except in metal hydrides = −1).
Group 1 metals: Always +1 in compounds.
Group 2 metals: Always +2 in compounds.
Sum rule: Oxidation numbers sum to 0 for neutral compounds, or to the ion charge for polyatomic ions.

Oxidation Numbers

Determine the oxidation number of the highlighted atom in each compound or ion.

Streak: 0 Best: 0

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