When an atom in a reactant gains electrons, what happens to its oxidation number?

Question

A.
Its oxidation number decreases.
B.
Its oxidation number doubles.
C.
Its oxidation number increases.
D.
Its oxidation number increases by one.
E.
Its oxidation number stays the same.

Answer 1

When an atom in a reactant gains electrons, it is reduced. The oxidation number of an atom is a reflection of the number of electrons it has relative to its elemental state. Gaining electrons means that the oxidation number decreases.

Therefore, the correct answer is:

A. Its oxidation number decreases.