Glenn Elert
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The Physics Factbook™
Edited by Glenn Elert -- Written by his students
An educational, Fair Use website
topic index | author index | special index
| Bibliographic Entry | Result (w/surrounding text) | Standardized Result |
|---|---|---|
| Sears, W. Francis. University Physics. New York. Addison Wesley, 1992: 596-603. | "Our physics books say that the diameter of a proton is 2 × 10-14 me [sic]" | 2 × 10-14 m |
| Christensen, James J. The Structure of an Atom. London: Wiley, 1990: 60-65. | "The structure is reflected in the size of nucleons which are about 10-15 m across" | 10-15 m |
| MIllikan, Robert Andrews. Electronics (+ and -) Protons, Photons, Neutrons, and Cosmic Rays. London: Cambridge University Press, 1990: 47. | "The radius of a proton is on the order of 10-13 cm" | 10-15 m |
| Brown, Jonathan. The Physical Science Encyclopedia. New York. Cornell University Press, 1980. | "The proton has a radius about 10-15 m" | 10-15 m |
| World Book Encyclopedia. Chicago: World Book, 1998: 69. | "A proton has a diameter of approximately one-millionth of a nanometer" | 10-15 m |
A proton is a nuclear particle that has a positive charge.Thischarge is equal in magnitude to that of an electron, but oppositein sign. Protons together with neutrons constitute all atomicnuclei. Protons and neutrons together are regarded as nucleons.The nuclear forces operating between a neutron and a proton aremuch stronger than the electrostatic forces existing between atomicand and molecular systems. The nuclear force between two nucleonsis considered separately from the electrostatic forces due toelectric charges that nucleons could carry. In addition mass,charge, spin, and diameter play an important role in the mechanicsof the nucleus.
Protons are the nuclei of the simplest element -- hydrogen.Protons also differentiate one element from the other because,every different element has a different number of protons. Positivelycharged hydrogen atoms were first identified as protons by J.J. Thompson in 1906. He found that the electric charge on a protonwas equal but opposite that of an electron. However, the massof a proton he found to much larger than that of an electron.
The current estimate for the size of a proton was shown byRutherford in his scattering experiment in 1911. Rutherford showedthat the nucleus of the atom is very small and dense comparedto the rest of the atom. Its diameter was later found to be onthe order of 10-15 m.
The angular pattern and energy distribution of scattered electronsgives us information about the internal structure of protons.In 1963, M. Gell-Mann proposed that a proton was composed of threespinning particles called quarks: two up quarks with acharge of +2/3 e (positive two-thirds the electron's charge)and one down quark with a charge of -1/3 e. This fractionallycharged quark concept was developed much further and has becomecentral to understanding the behavior and structure of protons.
Yelena Meskina -- 1999
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