What is needed from the valence shell to participate in electrical current flow?

For electrical current flow, electrons are the key participants. In an atom, the valence shell contains electrons that are involved in chemical bonding and electrical conductivity. When an electric field is applied, these valence electrons can be freed from their atoms, allowing them to move through a conductor. This movement of electrons is what constitutes electric current.

Protons and neutrons, located in the nucleus of the atom, do not participate in current flow because they are bound in the atomic structure and do not move freely in response to electric fields. Ions can participate in current flow in specific scenarios, such as in electrolysis or ionic solutions, but in the context of solid conductors and typical discussions of electricity, it is the free electrons in the valence shell that are the main contributors to electrical conduction. Thus, free electrons are essential for enabling electric currents in conductive materials.