All electrons are alike. All protons are alike. The number of protons associated with the nucleus of an atom identifies it as a specific element. Electrons have a tiny fraction of the mass of a proton. Under normal conditions, electrons are bound—that is, held in their orbital shells—to the positively charged nuclei of atoms by the attraction between opposite electrical charges.
Any atom may possess more or fewer electrons than protons. An atom with an excess or deficit of electrons retains the character of the element. Such an atom is described as negatively (an excess of electrons) or positively (a net deficit of electrons) charged and is known as an ion. For instance, a copper atom with a shortage or deficit of electrons could be called a positive copper ion, meaning that it would be inclined to steal electrons from other substances.