How does reduction affect an atom's oxidation state?

Reduction is a chemical process that involves the gain of electrons by an atom or molecule. When an atom gains electrons, its oxidation state decreases, reflecting a reduction in charge. In the context of oxidation states, each electron that is accepted effectively lowers the positive charge or increases the negative charge associated with the atom. Thus, when considering the effect of reduction on an oxidation state, the correct response is that it decreases the oxidation state by gaining electrons.

This concept is a fundamental aspect of redox reactions, where reduction (the gain of electrons) occurs alongside oxidation (the loss of electrons). Understanding that gaining electrons leads to a decrease in oxidation state is crucial for analyzing chemical reactions and predicting how different species will interact.