Question

In a redox reaction, why does an element’s oxidation number decrease? A. An element’s oxidation number decreases because it gained electrons. B. An element’s oxidation number decreases because it exchanged electrons. C. An element’s oxidation number decreases because it lost electrons. D. An element’s oxidation number decreases because it was heated.

Answer 1

The answer is A - when it has gained electrons.

Oxidation is usually a LOSS of electrons (think OIL RIG - oxidation is loss reduction is gain). Losing electrons would increase the oxidation number.

However since number has decreased here, that means there is a gain of electrons!