Edexcel A-Level Chemistry 9CH0
Atomic Structure and the Periodic Table
Bonding and Structure
Inorganic Chemistry and the Periodic Table
Formulae, Equations and Amounts of Substance
Organic Chemistry I
Modern Analytical Techniques I
Energetics I
Kinetics I
Equilibrium I
Acid-Base Equilibria
Energetics II
Redox II
Transition Metals
Kinetics II
Organic Chemistry II
Organic Chemistry III
Redox I
Oxidation numbers
- 4 things to know
- Papers 1, 2 and 3
Overview
Recall questions on the rules for assigning oxidation numbers, on working them out in ions and compounds, and on what a Roman numeral in a name means.
What you need to know
Answer each one before you reveal it.
What does a Roman numeral in a name tell you?
What does an element's oxidation number mean?
What is the oxidation number of a simple monatomic ion?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What does an element's oxidation number mean?
Model answer
The charge an atom would have if all the bonds in the species were treated as fully ionic.
- 2
What is the oxidation number of an atom in an uncombined element?
Model answer
Zero.
- 3
What is the oxidation number of a simple monatomic ion?
Model answer
Equal to the charge on the ion (e.g. Na⁺ is +1, Cl⁻ is -1).
- 4
What is the usual oxidation number of oxygen, and its exceptions?
Model answer
Usually -2; it is -1 in peroxides and +2 in the compound with fluorine (OF₂).
- 5
What is the usual oxidation number of hydrogen, and its exception?
Model answer
Usually +1; it is -1 in metal hydrides such as NaH.
- 6
What is the oxidation number of fluorine in its compounds?
Model answer
Always -1.
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