Proton
For alternative meanings see proton (disambiguation).| Proton |
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| Classification |
|---|
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| - | Properties |
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-| Mass: | 1.672 621 71(29) × 10âˆ'27 kg | | 938.272 029(80) MeV/c2 | | Electric Charge: | 1.602 176 53(14) × 10âˆ'19 C | | Diameter: | about 1.5×10âˆ'15 m | | Spin: | ½ | | Quark Composition: | 1 down, 2 up | |
|
In
physics, the
proton (
Greek proton = first) is a
subatomic particle with an
electric charge of one positive
fundamental unit (1.602 × 10
âˆ'19 coulomb), a diameter of about 1.5×10
âˆ'15 m, and a mass of 938.3
MeV/
c2 (
1.6726 × 10−27 kg), or about 1836 times the mass of an
electron. The proton is observed to be
stable, with a lower limit on its
half-life of about 10
35 years, although some theories predict that the
proton may decay. The proton has a
density of about 2.31 × 10
17 kg m
−3.
Protons are
spin-1/2
fermions and are composed of three
quarks, making them
baryons. The two
up quarks and one
down quark of the proton are also held together by the
strong nuclear force, mediated by
gluons. Protons may be transmuted into
neutrons by
inverse beta decay (that is, by capturing an
electron); since neutrons are heavier than protons, this process does not occur spontaneously but only when energy is supplied. The proton's
antimatter equivalent is the
antiproton, which has the
same magnitude charge as the proton but the opposite sign.
Protons and neutrons are both
nucleons, which may be bound by the
nuclear force into
atomic nuclei. The most common isotope of the
hydrogen atom is a single proton. The nuclei of other atoms are composed of various numbers of protons and neutrons. The number of protons in the nucleus determines the chemical properties of the atom and which
chemical element it is.
In
chemistry and
biochemistry, the proton is thought of as the
hydrogen ion, denoted H
+. In this context, a proton donor is an
acid and a proton acceptor a
base (see
acid-base reaction theories).
Ernest Rutherford is generally credited with the discovery of the proton. In 1918 Rutherford noticed that when
alpha particles were shot into
nitrogen gas, his
scintillation detectors showed the signatures of hydrogen nuclei. Rutherford determined that the only place this hydrogen could have come from was the nitrogen, and therefore nitrogen must contain hydrogen nuclei. He thus suggested that the hydrogen nucleus, which was known to have an
atomic number of 1, was an elementary particle. Prior to Rutherford,
Eugene Goldstein had observed
canal rays, which were composed of positively charged ions.
After the discovery of the electron by J.J.Thompson Goldstein tried to suggested that since the atom is electricaly neutral there must be a positivly charged partical in the atom and tried to discover it.He used the canal rays once again and this time used a perforated disk like the cathode. After the electron had been removed from the particals inside the cathode ray tube they became positivly charged and moved towards the cathode. Most of the charged paricals passed through the cathode, it being perforated, and produced a glow on the glass by exciting the glass particals. Goldstein was now satisfied that he had discovered the proton. When he calculated the Charge/Mass of this new partical (which in case of the electron was found to be the same for every gas that was used in the cathode ray tube) was found to be different when the gas used was changed. The reason was simple. What Goldstien assumed to be a proton was actually an ion. He gave up his work there. Years Later Radio-activity was discovered. Wilson Cloud Chamber was used to photograph the tracks of the Alpha-Particals. Wilson cloud chamber used the ionisation power of these particals to photograph them. While observing the tracks in the Wilson cloud chamber the scientests found that some of the tracks were forked. These type of tracks were mostly found in case of nitrogen. One day a forked track moving downwards was obsereved. When this parical was tested it was found to be a hydrogen ion and the gas left in the chamber was found to be oxygen whereas nitrogen had been taken for the experement. The problem now was that the length of the track was longer than could be expected from a hydrogen ion. This partical was concluded to be a proton.
The
antiproton is the
antiparticle of the proton. It was discovered in 1955 by
Emilio Segre and
Owen Chamberlain, for which they were awarded the 1959
Nobel Prize in Physics.
CPT-symmetry puts strong constraints on the relative properties of particles and
antiparticles and, therefore, is open to stringent tests. For example, the charges of the proton and antiproton must sum to exactly zero. This equality has been tested to one part in 10
8. The equality of their masses is also tested to better than one part in 10
8. By holding antiprotons in a
Penning trap, the equality of the charge to mass ratio of the proton and the antiproton has been tested to 1 part in 9×10
11. The
magnetic moment of the antiproton has been found with error of 8×10
−3 nuclear
Bohr magnetons, and is found to be equal and opposite to that of the proton.
Due to their stability and large mass (compared to
electrons), protons are well suited to use in
particle colliders such as the
Large Hadron Collider at
CERN. Protons also make up a large majority of the
cosmic rays which impinge on the
Earth's atmosphere. Such high-energy proton collisions are more complicated to study than electron collisions, due to the composite nature of the proton. Understanding the details of proton structure requires
quantum chromodynamics.
*
particle physics*
subatomic particle*
quark model*
neutron*
proton-proton chain reaction*
proton pump*
proton pump inhibitor*
proton therapy*
list of particles*
fermion field* CODATA values for
proton mass,
proton mass energy equivalent*The following analysis addresses the problem of proton creation and it's integrated in the concepts of the Physics of Creation::Aspden, Harold (2003),
Physics of Creation:
The Creation of the Proton (Chapter 4), PhD. Physics - University of Cambridge [1953], U.K. [pdf file]
*
Particle Data Group*
Large Hadron Collider
