Transfer of electrons occurs in redox (oxidation-reduction) reactions between
species (A chemical entity. Chemical entities can be ions, molecules, elements .....) known as
- the oxidant (electron acceptor) and
- the reductant (electron donor)
The oxidant is also known as the oxidizing agent.
The reductant is also known as the reducing agent.
Consider the redox reaction:
Cu
2+(aq) + Zn(s)

Cu(s) + Zn
2+(aq)
The oxidant is Cu2+(aq) and the reductant is Zn(s).
The product arising from the
oxidant has a more negative charge because the oxidant (oxidizing agent) has accepted electrons
In this example: Cu2+ gives Cu
reductant has a more positive charge because the reductant (reducing agent) has donated electrons
In this example: Zn gives Zn2+
The direction of the change in charge for species containing a single type of atom is an important clue as to whether the species is an oxidant or a reductant.
If the charge becomes more positive, the species is a reductant.
If the charge becomes more negative, the species is an oxidant.