Elementary Particle
AccessScience from McGraw-Hill Education Page 1 of 8 www.accessscience.com Elementary particle Contributed by: Frank E. Close Publication year: 2018 Key Concepts • Elementary particles are the most fundamental components of matter and cannot be further subdivided into smaller constituents. • Elementary particles include quarks (the constituents of protons and neutrons), leptons (electrons, muons, taus, and neutrinos), gauge bosons (photons, gluons, and W and Z bosons) and the Higgs boson. • The fundamental forces that act on elementary particles are the electromagnetic force, the strong force, the weak force, and gravity. • Characteristics of elementary particles include mass, spin, and charge. • To each kind of elementary particle there corresponds an antiparticle, or conjugate particle, which has the same mass and spin, but has the opposite value of charge and ∕ or flavor quantum number. • The standard model of particle physics classifies and describes the behavior of all known elementary particles. Fundamental, irreducible units that constitute the matter of the universe and express the forces of nature. The standard model of particle physics, which emerged in the 1970s, classifies and describes the 17 known elementary particles in terms of their properties such as mass, spin and charge (Fig. 1 and table). See also: ELECTRIC CHARGE ; MASS ; SPIN (QUANTUM MECHANICS) ; STANDARD MODEL . Our identification of the elementary particles has evolved with our understanding of matter. The idea that everything is made from a few basic elements originated in ancient Greece. In the nineteenth century, the elementary pieces of matter were believed to be the atoms of the chemical elements, but in the first half of the twentieth century, atoms were found to be made up of electrons, protons, and neutrons.
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