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Oxidation and Reduction. Chem 1061 – Tro , Chapter 4 Lance S. Lund. Assigning Oxidation Numbers. The oxidation number of an element is zero. The oxidation number of an atom in a monoatomic ion equals the charge on the ion.
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Oxidation and Reduction Chem 1061 – Tro, Chapter 4 Lance S. Lund
Assigning Oxidation Numbers • The oxidation number of an element is zero. • The oxidation number of an atom in a monoatomic ion equals the charge on the ion. • The oxidation number of oxygen is -2 in most of its compounds. Exception: In peroxides, the oxidation number of oxygen is -1. • The oxidation number of hydrogen is +1 in most of its compounds. Exception: In hydrides, the oxidation number of hydrogen is -1.
Assigning Oxidation Numbers • The oxidation number of fluorine is -1 in all of its compounds. Each of the halogens has an oxidation number of -1 in binary compounds, except when the other element is a halogen above it in the Periodic Table or the other element is oxygen. • The sum of oxidation numbers of the atoms in a compound is zero. The sum of the oxidation numbers of the atoms in a polyatomic ion equals the charge on the ion.
Determine the Oxidation Numbers • Determine the oxidation numbers of each element in the following species: • K2SO4 H3PO4 • Cr2O72- Br2
Redox Reactions • The Loss of Electrons is Oxidation • An element that loses electrons is said to be oxidized. The species in which that element is present in a reaction is called the reducing agent. • The Gain of Electrons is Reduction • An element that gains electrons is said to be reduced. The species in which that element is present in a reaction is called the oxidizing agent.