Electron Definition - Chemistry Glossary

Chemistry Glossary Definition of Electron

An electron is a negatively charged unit of matter.
An electron is a negatively charged unit of matter. Science Photo Library - MEHAU KULYK, Getty Images

Electron Definition

An electron is a stable negatively charged component of an atom. Electrons exist outside of and surrounding the atom nucleus. Each electron carries one unit of negative charge (1.602 x 10-19 coulomb) and has a very small mass as compared with that of a neutron or proton. Electrons are much less massive than protons or neutrons. The mass of an electron is 9.10938 x 10-31 kg. This is about 1/1836 the mass of a proton.

In solids, electrons are the primary means of conducting current (since protons are larger, typically bound to a nucleus, and thus more difficult to move). In liquids, current carriers are more often ions.

The possibility of electrons was predicted by Richard Laming (1838-1851), Irish physicist G. Johnstone Stoney (1874), and other scientists. The term "electron" was first suggested by Stoney in 1891, although the electron was not discovered until 1897, by British physicist J.J. Thomson.

A common symbol for an electron is e-. The electron's antiparticle, which carries a positive electric charge, is called a positron or antielectron and is denoted using the symbol β-. When an electron and a positron collide, both particles are annihilated and gamma rays are released.

Electron Facts

  • Electrons are considered to be a type of elementary particle because they are not made up of smaller components. They are a type of particle belonging to the lepton family and have the smallest mass of any charged lepton or other charged particle.
  • In quantum mechanics, electrons are considered to be identical to each other because no intrinsic physical property may be used to distinguish between them. Electrons may swap positions with each other without causing an observable change in a system.
  • Electrons are attracted to positive-charged particles, such as protons.
  • Whether or not a substance has a net electric charge is determined by the balance between the number of electrons and the positive charge of atomic nuclei. If there are more electrons than positive charges, a material is said to be negatively charged. If there is an excess of protons, the object is considered to be positively charged. If the number of electrons and protons is balanced, a material is said to be electrically neutral.
  • Electrons can exist free in a vacuum. They are called free electrons. Electrons in a metal behave as if they were free electrons and can move to produce a net flow of charge termed an electric current. When electrons (or protons) move, a magnetic field is generated.
  • A neutral atom has the same number of protons and electrons. It can have a variable number of neutrons (forming isotopes), since neutrons do not carry a net electric charge.
  • Electrons have properties of both particles and waves. They can be diffracted, like photons, yet can collide with each other and other particles, like other matter.
  • Atomic theory describes electrons as surrounding the proton/neutron nucleus of an atom in shells. While it's theoretically possible for an electron to be found anywhere in an atom, it is most probably to find one in its shell.
  • An electron has a spin or intrinsic angular momentum of 1/2.
  • Scientists are capable of isolating and trapping a single electron in a device called a Penning trap. From examining single electrons, researchers have found the largest electron radius is 10-22 meters. For most practical purposes, electrons are assumed to be point charges, which are electrical charges with no physical dimensions.
  • According to the Big Bang theory of the universe, photons had sufficient energy within the first millisecond of the explosion to react with each other to form electron-positron pairs. These pairs annihilated each other, emitting photons. For unknown reasons, there came a time when there were more electrons than positrons and more protons than antiprotons. The surviving protons, neutrons, and electrons began to react with each other, forming atoms.
  • Chemical bonds are the result of transfers or sharing of electrons between atoms. Electrons are used in many applications, too, such as vacuum tubes, photomultiplier tubes, cathode ray tubes,  particle beams for research and welding, and the free-electron laser.
  • The words "electron" and "electricity" trace their origins to the ancient Greeks. The ancient Greek word for amber was elektron. The Greeks noticed rubbing fur with amber caused the amber to attract small objects. This is the earliest recorded experimentation with electricity. The English scientist William Gilbert coined the term "electricus" to refer to this attractive property.