As soon as it happens to meet with an unknown subject, the question of a mercantile worldly question necessarily arises - how much does it weigh. But if this is unknown - an elementary particle, then what? But nothing, the question remains the same: what is the mass of this particle. If someone were involved in calculating the costs incurred by mankind to satisfy their curiosity in researching, or rather, measuring, the mass of elementary particles, then we would find out that, for example, the mass of a neutron in kilograms with an amazing number of zeros after a decimal point would cost mankind more, than the most expensive construction with the same number of zeros.
And it all began very mundane: in the laboratory led by J.J. Thomson in 1897, studies of cathode rays were carried out. As a result, the universal constant for the Universe was determined - the magnitude of the ratio of the mass of an electron to its charge. Before determining the mass of an electron, there is very little left to determine its charge. After 12 years, Robert Millikan managed to do this. He conducted experiments with droplets of oil falling in an electric field, and he managed not only to balance their weight with the field, but also to carry out the necessary and extremely subtle measurements. Their result is the numerical value of the electron mass:
me = 9.10938215 (15) * 10-31kg.
At that time, studies of the structure of the atomic nucleus also took place, where Ernest Rutherford was the pioneer. It was he who, observing the scattering of charged particles, proposed a model of an atom with an external electron shell and a positive nucleus. The particle, which was proposed in the planetary model of the atom the role of the nucleus of a simple atom, was obtained during the bombardment of nitrogen by a stream of alpha rays. This was the first nuclear reaction obtained in the laboratory - as a result of it, oxygen and the nuclei of future hydrogen atoms called protons were obtained from nitrogen. However, alpha rays are composed of complex particles: in addition to two protons, they contain two more neutrons. The mass of the neutron is almost equal to the mass of the proton and the total mass of the alpha particle is quite solid in order to destroy the oncoming nucleus and to break off a “piece” of it, which happened.
The flux of positive protons was deflected by the electric field, compensating for its deviation caused by gravity. In these experiments, it was no longer difficult to determine the mass of the proton. But the most interesting was the question of what correlation the mass of the proton and the electron have. The riddle was immediately solved: the mass of the proton exceeds the mass of the electron a little more than 1836 times.
So, initially, the atom model was supposed, according to Rutherford, as an electron-proton set with the same number of protons and electrons. However, it soon turned out that the primary nuclear model does not completely describe all the observed effects on the interactions of elementary particles. Only in 1932, James Chadwick confirmed the hypothesis of additional particles in the composition of the nucleus. They were called neutrons, neutral protons, because they had no charge. It is this circumstance that determines their great penetrating ability - they do not spend their energy on the ionization of counter atoms. The neutron mass slightly exceeds the mass of the proton - only about 2.6 electron masses more.
The chemical properties of substances and compounds that are formed by this element are determined by the number of protons in the atomic nucleus. Over time, the participation of the proton in strong and other fundamental interactions was confirmed: electromagnetic, gravitational, and weak. Moreover, despite the fact that the neutron charge is absent, in strong interactions, the proton and neutron are considered as an elementary particle nucleon in different quantum states. In part, the similarity in the behavior of these particles is also explained by the fact that the neutron mass differs very little from the mass of the proton. The stability of protons allows them to be used, having previously been accelerated to high speeds, as bombarding particles for nuclear reactions.