An electron is a subatomic particle. Carrying a negative charge, an electron orbits an atom’s nucleus and is bound to it by electromagnetic forces. An electron has a mass that is minuscule in comparison with even the smallest of atoms, coming in at about one thousandth the size of the tiniest atom. The electron is a basic unit of nature, meaning it cannot be broken down into smaller units.

The electron plays a starring roll in many of the interactions we see on a daily basis. For example, electrons are partially responsible for the fact that we can stand on a flat surface and not sink right through it. This occurs as the result of the mutual repulsion of the electrons in both the ground and a person’s shoes. We also depend on electrons for electrical current to power electronic devices. Even televisions rely on electrons to function properly.

G. Johnstone Stoney, an Irish physicist, was credited with introducing the electron concept in 1874, as well as with naming it twenty years later. In 1897, J.J. Thompson, from Cambridge University, discovered that the electron was a subatomic particle. It wasn’t until 1909 that the charge of the electron was measured by Professor Robert Andrews Millikan, an American experimental physicist. He discovered its charge while conducting an oil-drop experiment.

Electrons are considered to be leptons. Leptons are considered fundamental particles, meaning they cannot be broken down into smaller units. Electrons, like other particles, are capable of acting in waves. The electron has an antiparticle, called the positron, that has the same mass as the electron. The positron, however, is positively charged.

The electric charge of the electron is −1.6022 × 10−19 coulomb. Its symbol is e−. An electron’s spin is ½ and it is a fermion, meaning it has a half-integer spin. Inside an atom, electrons are bound to the atom. When electrons are moving freely through space or another medium, however, they are referred to as free electrons. Electrons that are moving freely can be used in an electron beam.

Free electrons are responsible for the generation of electric current. In fact, it is free electrons that generate electric current. Electrons are used in numerous applications, including those related to industry, science, and medicine. Electrons are also present throughout the universe in incredibly large numbers.