General chemistryLesson 1 of 2 in the course Electrochemistry

Oxidation Numbers and Redox Half-Reaction Balancing

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

Oxidation numbers provide a consistent way to track how electrons are redistributed in chemical reactions. This lesson introduces the rules for assigning oxidation numbers and shows how they help identify redox changes.

An oxidation number, also called an oxidation state, is a formal bookkeeping value that describes an atom’s electron environment relative to the pure element. It is not necessarily the atom’s actual charge in a covalent molecule.

All flashcards

Oxidation number
A formal bookkeeping value found by assigning bonding electrons to the more electronegative atom.
Redox reaction
A reaction in which the oxidation number of one or more elements changes.
Oxidation
An increase in oxidation number that corresponds to loss of electrons.
Reducing agent
A substance that supplies electrons and is itself oxidized.
Half-reaction
An equation showing one part of a redox process and its electron transfer.

Quiz questions

  1. In a redox reaction, what happens to an oxidizing agent?Answer: It accepts electrons and is reduced.
  2. What distinguishes a redox reaction from a reaction with no redox change?Answer: At least one element changes oxidation number.
  3. When balancing oxygen atoms in an acidic-solution half-reaction, which species is added?Answer: Water
  4. What must happen to electrons when balanced half-reactions are added to form an overall reaction?Answer: They must cancel from the overall equation.
  5. When converting an acidic balancing result for a basic solution, what is added to both sides to neutralize hydrogen ions?Answer: Hydroxide ions in an equal amount

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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