What is the difference between bound and free electrons?

Bound electrons are the electrons locked in orbit of the atom which are held in orbit by its attraction to the positive charge of the proton(s) in the nucleus. Electrons have a negative charge. Conversely, the free electrons are electrons that are not orbiting the nucleus of an atom normally in the form of static electricity. Valence electrons are the electrons orbiting the outermost shell of the atom are weakly held by the positive proton charges and can be transferred to or shared with one or more other atoms. Valence electrons are bound until they are freed by some outside force or reaction.