Final answer:
In ordinary chemical reactions, electrons can be added to atoms, lost by atoms, or shared with other atoms. However, it is unlikely for a chemical reaction to produce excess electrons after completion, as this goes against the principle of chemical stability.
Step-by-step explanation:
In ordinary chemical reactions, the nucleus of each atom (and thus the identity of the element) remains unchanged. Electrons, however, can be added to atoms by transfer from other atoms, lost by transfer to other atoms, or shared with other atoms. The transfer and sharing of electrons among atoms govern the chemistry of the elements. During the formation of some compounds, atoms gain or lose electrons, and form electrically charged particles called ions.
However, in terms of a chemical reaction generating excess electrons after completion, it is unlikely and goes against the fundamental principles of chemical stability. In normal chemical reactions, ions or compounds are formed with no surplus electrons, as the sharing or transfer of electrons is driven by the desire for each atom to achieve a stable electron configuration. If excess electrons were produced after the completion of a reaction, it would indicate an imbalance and instability in the system.