August 15, 2022

In physics, the electron (from classical Greek ἤλεκτρον ḗlektron 'amber'), commonly represented by the symbol e−, is a subatomic particle with a negative elementary electrical charge.[8] An electron has no known components or substructure; in other words, it is generally defined as an elementary particle. In string theory an electron is said to be made up of a substructure (strings).[2] It has a mass that is approximately 1836 times less than that of the proton.[9] The intrinsic angular momentum (spin) of the electron is a half-integer value in units of ħ, which means that it is a fermion. Its antiparticle is called a positron: it is identical except for the fact that it has charges —among them, the electric one— of opposite sign. When an electron collides with a positron, the two particles can be totally annihilated and produce gamma-ray photons. Electrons, which belong to the first generation of the lepton family of particles,[10] participate in fundamental interactions, such as gravity, electromagnetism, and the weak nuclear force.[11] Like all matter, they possess quantum-mechanical properties of both particles and waves, in such a way that they can collide with other particles and can be diffracted like light. This duality is best demonstrated in experiments with electrons because of their tiny mass. Since electrons are fermions, no two of them can occupy the same quantum state, according to the Pauli exclusion principle.[10] The concept of an indivisible quantity of electric charge was theorized to explain the chemical properties of atoms. The first to work on it was the British natural philosopher Richard Laming in 1838.[4] The name electron for this charge was introduced in 1894 by the Irish physicist George Johnstone Stoney. However, the electron was not identified as a particle until 1897 by Joseph John Thomson and his team of British physicists.[6][12][13] In many physical phenomena—such as electricity, magnetism, or thermal conductivity—electrons play an essential role. A moving electron generates an electromagnetic field and is in turn deflected by external electromagnetic fields. When an electron is accelerated, it can absorb or radiate energy in the form of photons. Electrons, along with atomic nuclei made up of protons and neutrons, make up atoms. However, electrons contribute less than 0.06% to the total mass of atoms. The same Coulomb force, which causes the attraction between protons and electrons, also causes electrons to bond. The exchange or sharing of electrons between two or more atoms is the main cause of chemical bonding.[14] Electrons can be created by beta decay of radioactive isotopes and in high-energy collisions, such as the entry of a cosmic ray in the atmosphere. On the other hand, they can be destroyed by positron annihilation, and can be absorbed during stellar nucleosynthesis. There are laboratory instruments capable of containing and observing individual electrons, as well as electron plasma. Also, some telescopes can detect electron plasma in outer space. Electrons have many applications, including electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gas ionization detectors, and particle accelerators.

History of the electron

The ancient Greeks noted that amber attracted small objects when rubbed against fur. Along with lightning, this phenomenon is one of the earliest known experiences of humans with electricity.