Understanding Reduction and Oxidation Reactions

Reduction

The loss of oxygen (or gain of electrons) by a substance.

Oxidation

The gain of oxygen (or loss of electrons) by a substance.

Reducing Agent

The substance that is oxidized (loses electrons) and brings about the reduction of another substance.

Oxidizing Agent

The substance that is reduced (gains electrons) and causes the oxidation of another substance.

Algebraic sum of the oxidation numbers in a neutral compound is

0

Algebraic sum of the oxidation numbers in a polyatomic ion is

equal to ion charge

Atoms in their elemental state

Oxidation # = 0 (e.g., Fe, H2, O2)

Monatomic ions

Oxidation # = charge of ion (e.g., F-, Fe3+)

Compounds w/ Group 1A

Oxidation # = +1 (e.g., NaCl, KNO3)

Compounds w/ group 2A

Oxidation # = +2 (e.g., MgO)

Compounds w/ Fluorine

Oxidation # = -1 (e.g., HF, ClF)

Compounds w/ Hydrogen

Oxidation # = +1 (e.g., H2O)

Compounds w/ Oxygen

Oxidation # = -2 (e.g., SO2, HClO4)

Compounds w/ Group 7A

Oxidation # = -1 (e.g., HCl)

Compounds w/ Group 6A

Oxidation # = -2 (e.g., PbS2)

O₂ is

oxidizing agent

The halogens (F, Cl, Br, I) are

oxidizing agents

Nitric acid (HNO₃) is

oxidizing agent

Dichromate ion (Cr₂O₇^2-) is

oxidizing agent

Permanganate ion (MnO₄^-) is

oxidizing agent

Hydrogen (H₂) is

reducing agent

Metals such as Na, K, Fe, and Al are

reducing agents

Carbon (C) is

reducing agent (reduces metal oxides)