IB Chemistry Topic S3.1.6 Oxidation States Revision Notes (SL/HL)

IB Chemistry Topic S3.1.6 Oxidation States Revision Notes (SL/HL) | RevisionDojo

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What is an Oxidation State?

Definition

Oxidation state

The oxidation state (or oxidation number) is a numerical value assigned to an atom in a compound. It is the hypothetical charge the atom would have if every bond were treated as fully ionic (bonding electrons assigned to the more electronegative atom).

In simpler terms, it tells us the hypothetical charge an atom would have if the bonding electrons were assigned to the more electronegative atom.
Oxidation states are vital for understanding redox reactions, where electrons are transferred between substances.
They help us identify which species is oxidized (loses electrons) and which is reduced (gains electrons).
The terms oxidation state and oxidation number mean the same thing and are used interchangeably.

Example

In water (H₂O), oxygen is more electronegative than hydrogen, so it "pulls" the shared electrons closer to itself. As a result:
Oxygen is assigned an oxidation state of −2 (it "gains" two electrons).
Each hydrogen atom is assigned an oxidation state of +1 (it "loses" one electron).

Conventions for Assigning Oxidation States

To assign oxidation states, chemists follow a systematic set of rules.
These rules ensure consistency and accuracy across different compounds.

Rule 1: Free Elements

The oxidation state of an atom in its elemental form is always 0.
This applies to:

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Note

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What is an Oxidation State?

Definition

Oxidation state

In simpler terms, it tells us the hypothetical charge an atom would have if the bonding electrons were assigned to the more electronegative atom.
Oxidation states are vital for understanding redox reactions, where electrons are transferred between substances.
They help us identify which species is oxidized (loses electrons) and which is reduced (gains electrons).
The terms oxidation state and oxidation number mean the same thing and are used interchangeably.

Example

In water (H₂O), oxygen is more electronegative than hydrogen, so it "pulls" the shared electrons closer to itself. As a result:
Oxygen is assigned an oxidation state of −2 (it "gains" two electrons).
Each hydrogen atom is assigned an oxidation state of +1 (it "loses" one electron).

Conventions for Assigning Oxidation States

To assign oxidation states, chemists follow a systematic set of rules.
These rules ensure consistency and accuracy across different compounds.

Rule 1: Free Elements

The oxidation state of an atom in its elemental form is always 0.
This applies to:

Definition

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Note

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Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

IB Chemistry S3.1.6 Oxidation States Notes

Structure 1. Models of the particulate nature of matter5 subtopics

Structure 2. Models of bonding and structure4 subtopics

Structure 3. Classification of matter2 subtopics

Reactivity 1. What drives chemical reactions?4 subtopics

Reactivity 2. How much, how fast and how far?3 subtopics

Reactivity 3. What are the mechanisms of chemical change?4 subtopics

What is an Oxidation State?

Conventions for Assigning Oxidation States

Rule 1: Free Elements

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Duis aute irure dolor in reprehenderit

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What is an Oxidation State?

Conventions for Assigning Oxidation States

Rule 1: Free Elements

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account