How does a reducing agent cause another substance to gain electrons?

A reducing agent causes another substance to gain electrons by donating electrons to it. This process is a fundamental aspect of oxidation-reduction (redox) reactions, where reduction is defined as an increase in the number of electrons associated with an atom or group of atoms. The substance that accepts these electrons is said to be reduced, while the reducing agent itself becomes oxidized.12

Redox reactions can be understood through the transfer of electrons, hydrogen atoms, or oxygen atoms, all of which involve a reciprocal transfer between substances. In the context of electron transfer, the reducing agent provides the electrons necessary for another substance to gain them, thereby increasing its electron count and undergoing reduction.324