Which statement is NOT true about oxidation numbers?

Which statement is NOT true about oxidation numbers?

• A. Sum Of Oxidation Numbers In A Neutral Molecule Equals Zero
• B. Monatomic Ion's Oxidation Number Equals Its Charge
• C. Oxygen Is Always -2
• D. Fluorine's Oxidation Number Is -1 In Most Compounds

Answer: (C)

Oxidation numbers are a bookkeeping tool used to track electron distribution in a compound and to balance redox changes. In a neutral molecule, all oxidation numbers must add up to zero, while in a polyatomic ion they add up to the ion’s charge. Oxygen is often -2 because it tends to gain two electrons when bonding with less electronegative elements. But this isn’t universal. In peroxides like H2O2, each oxygen is -1; in superoxide ions the average oxidation state of oxygen is -1/2; in compounds such as OF2, oxygen is actually +2. These examples show that oxygen is not always -2. Fluorine is -1 in nearly all compounds because it is the most electronegative element, and it only has 0 oxidation number in its diatomic form, F2.

Oxidation numbers are a bookkeeping tool used to track electron distribution in a compound and to balance redox changes. In a neutral molecule, all oxidation numbers must add up to zero, while in a polyatomic ion they add up to the ion’s charge. Oxygen is often -2 because it tends to gain two electrons when bonding with less electronegative elements. But this isn’t universal. In peroxides like H2O2, each oxygen is -1; in superoxide ions the average oxidation state of oxygen is -1/2; in compounds such as OF2, oxygen is actually +2. These examples show that oxygen is not always -2. Fluorine is -1 in nearly all compounds because it is the most electronegative element, and it only has 0 oxidation number in its diatomic form, F2.