2.9 Redox & Oxidation Numbers

Exam 2

What is a redox reaction?

A chemical reaction where electrons are transferred between substances.

What does oxidation mean?

Loss of electrons (OIL – Oxidation Is Loss).

What does reduction mean?

Gain of electrons (RIG – Reduction Is Gain).

What is the oxidizing agent?

The substance that causes reduction (it gets reduced itself).

What is the reducing agent?

The substance that causes oxidation (it gets oxidized itself).

What is an oxidation number?

A number assigned to an element in a compound that shows the number of electrons lost or gained.

What is the oxidation number of an element in its pure form (like O₂ or Na)?

0

What is the oxidation number of oxygen in most compounds?

-2

What is the oxidation number of hydrogen in most compounds?

+1

How do you know if an element was oxidized or reduced?

If its oxidation number increases → oxidized; if it decreases → reduced.