Reduction is a chemical process that involves the gain of electrons, a decrease in oxidation number, gain of hydrogen atoms, and loss of oxygen atoms in a substance.
Gain of Electrons
When a substance gains electrons during a chemical reaction, it is said to undergo reduction. This occurs when the substance is reduced, and its oxidation number decreases.
Example: In the reaction, chlorine undergoes reduction because it gains an electron.
Equation: Cl + 2e- → 2Cl
Decrease in Oxidation Number
Reduction is also defined as a decrease in the oxidation number of a chemical species. The oxidation number is a measure of the number of electrons that an atom has gained or lost in a compound. When an atom gains electrons, its oxidation number decreases, and it undergoes reduction.
Example: In the reaction between copper oxide and hydrogen gas to form copper metal and water, copper undergoes reduction because its oxidation number decreases from +2 to 0.
Equation: CuO + H → Cu + HO
Gain of Hydrogen Atom
Reduction can also refer to the gain of hydrogen atoms in a chemical reaction. This is because hydrogen atoms carry a positive charge, and their addition leads to the reduction of the substance.
Example: In the reaction between nitrogen and hydrogen to form ammonia, nitrogen undergoes reduction because it gains three hydrogen atoms.
Equation: N + 3H → 2NH
Loss of Oxygen Atom
Reduction can also refer to the loss of oxygen atoms in a substance during a chemical reaction. Oxygen atoms carry a negative charge, and their loss leads to the reduction of that substance.
Example: In the reaction between iron oxide and aluminum, iron oxide undergoes reduction because it loses oxygen atoms.
Equation: FeO + 2 Al → AlO + 2 Fe
