Oxidation Number and Rules for its Assignment
Definition of oxidation number and mastering the rules for assigning it to elements in various compounds and ions.
What is Oxidation Number and Rules for its Assignment?
A number assigned to an element in a chemical combination which represents the number of electrons lost or gained by an atom of that element in order to form the compound.
Key points
- Define oxidation number.
- State and apply the rules for assigning oxidation numbers.
- Determine the oxidation number of an element in a given compound or ion.
- Identify oxidizing and reducing agents based on oxidation numbers.
Common exam trap
Forgetting the exceptions to the rules (e.g., oxygen in peroxides, hydrogen in metal hydrides).
Definitions
- Term
Oxidation Number
- Meaning
A number assigned to an element in a chemical combination which represents the number of electrons lost or gained by an atom of that element in order to form the compound.
- Term
Redox Reaction
- Meaning
A chemical reaction in which oxidation and reduction occur simultaneously, involving a change in oxidation numbers of reacting species.
Learning objectives
Define oxidation number.
State and apply the rules for assigning oxidation numbers.
Determine the oxidation number of an element in a given compound or ion.
Identify oxidizing and reducing agents based on oxidation numbers.
Prerequisites
Basic understanding of atomic structure (protons, electrons).
Concept of chemical bonds (ionic and covalent).
Periodic table and trends of elements.
Common mistakes
Forgetting the exceptions to the rules (e.g., oxygen in peroxides, hydrogen in metal hydrides).
Incorrectly applying the rule for the sum of oxidation numbers in polyatomic ions.
Confusing oxidation number with actual charge.
Not considering the electronegativity difference when assigning oxidation numbers to elements in a compound.
Keywords
Oxidation Number
Oxidation State
Redox
Oxidation
Reduction
Rules for Oxidation Number
Oxidizing Agent
Reducing Agent
Practice preview
What is the oxidation number of hydrogen in H2O and in NaH, respectively?…
easy
Calculate the oxidation number of sulfur in the sulfate ion, SO4^2-.…
medium
In most of its compounds, what is the oxidation number of an alkali metal?…
easy