The mass of a neutron, a proton, an electron - what is common?

As soon as it happens to meet an unknown object, it is necessarily a mercantile-everyday question - and how much it weighs. But if this unknown is an elementary particle, what then? But nothing, the question remains the same: what is the mass of this particle. If someone were busy calculating the costs incurred by mankind in order to satisfy his curiosity about research, or rather measuring, the masses of elementary particles, we would have learned that, for example, the mass of a neutron in kilograms with an astonishing number of zeros after a comma cost humanity more, Than the most expensive construction with the same number of zeros to the comma.

And everything began very uneventfully: at the laboratory headed by JJ Thomson in 1897, investigations of cathode rays were carried out. As a result, the universal constant for the Universe was determined - the value of the ratio of the electron mass to its charge. Before determining the mass of an electron, it remains very little - to determine its charge. In 12 years Robert Milliken managed to do it. He experimented with droplets of oil falling in the electric field, and he managed not only to balance their weight with the size of the field, but also to make necessary and extremely delicate measurements. Their result is the numerical value of the electron mass:

Me = 9,109,38215 (15) * 10-31kg.

By this time, there are also studies of the structure of the atomic nucleus, where the pioneer was Ernest Rutherford. It was he who, observing the scattering of charged particles, proposed an atom model with an external electron shell and a positive nucleus. The particle, which was proposed in the planetary model of the atom as the nucleus of the simplest atom, was obtained by bombarding nitrogen with an alpha-ray stream. This was the first nuclear reaction received in the laboratory - as a result of it, oxygen was produced from the nitrogen and the nuclei of future hydrogen atoms called protons. However, alpha rays consist 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 turns out to be quite solid in order to destroy the counter nucleus and to chop off a "piece" from it, which happened.

The flow of positive protons was deflected by the electric field, compensating for its deviation caused by gravity. In these experiments, it was not difficult to determine the proton mass. But the most interesting was the question of what proportion the mass of a proton and an 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 model of the atom was assumed, according to Rutherford, as an electron-proton complex with the same number of protons and electrons. However, very soon it 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 nucleus. They were called neutrons, neutral protons, tk. They did not have a charge. It is this circumstance that determines their great penetrating power - they do not expend their energy on the ionization of opposing atoms. The neutron mass is quite insignificantly larger than the proton mass - 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 nucleus of the atom. Over time, the participation of the proton in strong and other fundamental interactions was confirmed: electromagnetic, gravitational and weak. In this case, in spite of the fact that there is no charge of the neutron, in strong interactions the proton and the neutron are treated as an elementary nucleon particle in different quantum states. Part of the similarity in the behavior of these particles is explained by the fact that the neutron mass differs very little from the mass of the proton. The stability of protons makes it possible to use them, previously accelerated to high velocities, as bombarding particles for nuclear reactions.