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Nuclear Power Plant Isar, Germany

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Proton

Proton

Definition of proton

A proton is a subatomic particle with positive electric charge that is inside the atomic nucleus of atoms. The number of protons in the atomic nucleus determines the atomic number of an element, as indicated in the periodic table of the elements.

The proton has charge +1 (or, alternatively, 1.602 x 10 -19  coulombs), exactly the opposite of the charge -1 that contains the electron. In mass, however, there is no competition - the mass of the proton is approximately 1,836 times greater than that of an electron.

The proton is classified as baryon, and is composed of three quarks (uud). The corresponding antiparticle, the antiproton, has the same characteristics as the proton but with a negative electric charge.

Characteristics of protons

Protons are composed of three 1/2 spin quarks. Protons are classified as baryons that are a subtype of hadrons. The two quarks above and one quark below the protons are held together by strong nuclear interaction. The proton has a positive charge distribution and decays exponentially.

Protons and neutrons are nucleons. Both are united in the nucleus by a strong nuclear force. The most common isotope of hydrogen is a nucleus with a proton. The nuclei of heavy hydrogen isotopes (deuterium and tritium) contain one proton and one or two neutrons, respectively. These two hydrogen isotopes are used as nuclear fuel in nuclear fusion reactions. All other types of atoms are composed of two or more protons and a different number of neutrons.

The atomic number of an atom is the number of protons in its nucleus. The number of protons in the nucleus of an atom determines its chemical properties. For this reason the chemical elements are represented by the number of protons in a nucleus (Z), that is, the atomic number. To determine the isotopes of an element, we also use the number of neutrons (N) by adding all the nucleons, and it is known as the mass number (A).

According to the flow of proton particle physics experiments, the proton is a stable particle, which means that it does not disintegrate into other particles and, therefore, within the experimental limits, its life is eternal. This point is summarized in the conservation of the number of baryons in the processes between elementary particles. In fact, the lightest baryon is precisely the proton and, if the baryon number is to be stored, it can not decay into any other lighter particle.

Decay of protons

Protons are stable from the point of view of the standard model of particle physics. The laws of physics do not allow a proton to decay spontaneously due to the preservation of the number of baryons. However, recently it has been proposed that the predominance of matter over antimatter in the universe results in a very slight imbalance in the proportion of matter / antimatter that occurred very early in its formation. After most of the matter and antimatter were destroyed, matter was all that remained of the baryonic matter in our current universe.

This means that essentially the law of conservation of the number of baryons does not break, but the decomposition of protons was the inevitable mechanism to return the number of baryons to the state of equilibrium, in the sense that it corrected the original imbalance in the universe for all the current matter. in our universe

The proton is stable by itself. In some rare types of radioactive decay they emit free protons, and the result of the decomposition of free neutrons in other decays. As a free proton, it has the ability to pick up an electron and become neutral hydrogen, which can react chemically very easily. There may be free protons in plasmas, cosmic rays or in the solar wind.

History of protons

Ernest Rutherford, discoverer of the proton.In 1886, Eugen Goldstein discovered anodic rays and showed that they were positively charged particles (ions) produced from gases. By varying the gases inside the tubes, Goldstein observed that these particles had different values ​​of charge to mass ratio. For this reason, the positive charge with a particle could not be identified, unlike the negative charges of electrons, discovered by Joseph John Thomson.

After the discovery of the atomic nucleus by Ernest Rutherford in 1911, Antonius Van den Broek proposed that the place of each element of the periodic table (its atomic number) was equal to its nuclear charge. This theory was confirmed experimentally by Henry Moseley, in 1913, using X-ray spectra.

In 1917, Rutherford showed that the hydrogen nucleus was present in other nuclei, a general result that is described as the discovery of the proton. Rutherford realized that, by bombarding alpha particles in pure nitrogen gas, his scintillation detectors showed the signs of hydrogen nuclei. Rutherford determined that hydrogen could only come from nitrogen and that, therefore, they must contain hydrogen nuclei. A hydrogen nucleus disintegrated by the impact of the alpha particle, and formed an oxygen atom -17 in the process. The hydrogen nucleus is, therefore, present in other nuclei as an elementary particle, what Rutherford called the proton, after the singular neuter of the Greek word meaning 'first', πρῶτον.

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Last review: March 19, 2019