We explain what protons are, how they were discovered, their properties and characteristics. Also, what are nucleons.
What is a proton?
The proton is a type of subatomic particle , that is, one of the minimum particles that make up the atom . It belongs to the family of fermions and is equipped with a positive electrical charge.
All matter is made of atoms , and these in turn of three types of particles, equipped with a different electric charge: electrons (negative charge), neutrons (neutral charge) and protons (positive charge).
For a long time it was thought that the proton was a fundamental type of particle, that is, that it could not be divided. However, today there is strong evidence to suggest that it is composed of quarks .
In any case, the proton is a stable subatomic particle, counterpart of the electron. Unlike the latter, which orbits around the nucleus of the atom, the protons are contained in the atomic nucleus next to the neutrons , contributing most of the atomic mass.
Protons were discovered in 1918 by Ernest Rutherford (1871-1937), a British chemist and physicist. Amid experiments with nitrogen gas, Rutherford noted that his instruments detected the presence of hydrogen nuclei by firing alpha particles at the gas.
He concluded that these nuclei must be fundamental particles of matter, without knowing at that time that, precisely, the nucleus of the hydrogen atom contains a single particle: a proton. Thus, it was decided to provide hydrogen with the atomic number 1 .
However, previous scientific experiences are known that led to this discovery . For example, the German physicist Eugene Goldstein (1850-1930) in 1886 deduced that, being the electrically neutral atom.
In addition, the British JJ Thompson (1856-1940) had already discovered electrons and their negative charge, that is, it was necessary that there be some other type of particle with opposite charge in the atom. However, in his search for these particles, Goldstein found positive ions, through experiments with cathode rays.
Properties and characteristics of the proton
Protons are stable composite particles , much more massive than an electron (1836 times) and endowed with a positive elementary charge of 1 (1.6 x 10 -19 C). They are composed of three elementary particles or quarks : two ” up ” (top) and one ” down ” (bottom). Their half-life is greater than 10 35 years , at which time they are susceptible to decomposition.
Protons have, like other subatomic particles, their own spin, that is, an intrinsic and invariable angular momentum, which in this case is ½ . This property is particularly useful for nuclear magnetic resonances and other modern technological applications.
Since they are usually found in the atomic nucleus, protons and neutrons are known as “nucleons . ” The electrons, on the other hand, orbit around them in a more or less dispersed way.
Nucleons are linked together by strong nuclear forces , which only in cases of particularly large atoms (such as Uranium) can yield to other forces, such as electromagnetic .
Nucleons constitute the largest percentage of the mass of any one atom , and therefore determine the difference between a chemical element and the other: for example, the hydrogen atom possesses only one proton in its nucleus, while that of helium possesses two protons and one or two neutrons, depending on the specific isotope.
The atomic number (Z) indicates how many protons a type of atom has in its nucleus. Each chemical element has a different atomic number, although its chemical behavior is rather determined by the number of electrons that orbit its nucleus.
Thus, for example, chlorine (Cl) has 17 protons in its nucleus, so that its atomic number is 17. This number never varies, even among the isotopes (versions) of the same atom, since they differ each other only by the number of neutrons in their nucleus.