• The oxidation numbers (also known as oxidation state) is a number given to each atom or ion in a compound to keep track of how many electrons they have
• In a single ion or molecular ion, the oxidation number tells us how many electrons have been lost or gained
• Positive oxidation number = loss of electrons
• Negative oxidation number = gain of electrons

Oxidation number rules

• The oxidation number (ox.no.) refers to a?single?atom in a compound

Worked example: Deducing oxidation numbers

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