Atoms are made of protons, neutrons, and electrons. Of these three particles, the electron has the smallest mass. Here is the definition of the electron, along with its word origin, history, and interesting facts.
An electron is a stable subatomic particle with a negative electrical charge. 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. The mass of an electron is 9.10938 x 10-31 kg. This is about 1/1836 the mass of a proton.
A common symbol for an electron is e–. The electron’s antiparticle, which carries a positive electric charge, is called a positron or antielectron. A positron is denoted using the symbol e+ or β+. When an electron and a positron collide, both particles are annihilated and energy is released in the form of gamma rays.
Where to Find Electrons
Electrons are found free in nature (free electrons) and bound within atoms. Electrons are responsible for the negatively-charged component of an atom. In an atom, electrons orbit around the positively-charged atomic nucleus.
In solids, electrons are the primary means of conducting current. This is because protons are bound within the nucleus, so they are not as mobile as electrons. In liquids, current carriers are more often ions. Interactions between the electrons of atoms and molecules produce chemical reactions. Chemical bonds form when electrons are shared between atoms.
History and Word Origin
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.
Although electron sciences dates to the 19th and 20th centuries, 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.
- 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.
- Protons and electrons have equal, but opposite charges. Electrons are attracted to positively-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 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.
- 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. These shells are regions of probability. Some are spherical, but other shapes also occur. While it’s theoretically possible to find an electron in the atomic nucleus, the highest probability of finding one is within 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. Because electrons are very small, they are treated like point charges, which are electrical charges with no physical dimensions.
- Matter is much more abundant than antimatter in the universe, but there may once have been equal numbers of electrons and positrons. According to the Big Bang theory, photons gained enough 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.
- Electrons are used in many practical applications. These include electricity, vacuum tubes, photomultiplier tubes, cathode ray tubes, particle beams for research and welding, and the free-electron laser.
- Buchwald, J.Z.; Warwick, A. (2001). Histories of the Electron: The Birth of Microphysics. MIT Press. pp. 195–203. ISBN 978-0-262-52424-7.
- Thomson, J.J. (1897). “Cathode Rays”. Philosophical Magazine. 44 (269): 293–316. doi:10.1080/14786449708621070