Which statement describes the process of oxidation?

1. Oxidation results in a gain of electrons, so the oxidation number decreases.
2. Oxidation results in a loss of electrons, so the oxidation number increases.
3. Oxidation results in a gain of electrons, so the oxidation number increases.
4. Oxidation results in a loss of electrons, so the oxidation number decreases.

4. Oxidation results in a loss of electrons, so the oxidation number decreases.