Once it was believed that the smallest unit of the structure of any substance - a molecule.Then, with the invention of more powerful microscopes, mankind was surprised to discover the concept of the atom - a composite particle molecules.It would seem that much less?Meanwhile, even after it became clear that the atom is in turn composed of smaller elements.
In the early 20th century British physicist Ernest Rutherford discovered the presence of the atom nucleus - the central structures, that moment marked the beginning of the endless series of discoveries relating to the smallest unit of matter structural element.
To date, based on the nuclear model of atomic structure, and thanks to numerous studies, it is known that the atom consists of a nucleus, which is surrounded by electron cloud. As part of the "cloud" - electrons, or elementary particles with a negative charge.In the nucleus, on the contrary, it consists of particles with a positive electrical charge, called protons.Already mentioned above
Proton in Greek means "the first mainstream" - an elementary particle related to the class baryons, ierelatively heavy particle.It is a stable structure, its lifetime is greater than 2.9 x 10 (29) years.
Strictly speaking, in addition to a proton, the nucleus of an atom also contains neutrons, which, on the basis of the name, neutrally charged.Both of these elements are called nucleons .
mass of a proton, because of circumstances quite obvious for a long time could not be measured.Now it is known that it is
mp = 1,67262 ∙ 10-27 kg.
It thus looks and the rest mass of the proton.
proceed to consider specific areas of physics different understandings of the proton mass.
mass of particles in the framework of the nuclear physics often takes a different view, it is a unit of measure amu
amu- Atomic mass unit.One amuequal to 1/12 of the mass of an atom of carbon, which equals the mass number 12. From 1 atomic mass unit is equal to 1.66057 · 10-27 kg.
mass of a proton, thus as follows:
mp = 1,007276 well.e. m.
There is another way to express the weight of the positively charged particles, using different measurement units.To do this, first you need to take for granted the equivalence of mass and energy E = mc2.Where c - speed of light, and m - mass of the body.
mass of the proton in this case will be measured in megaelectronvolts or MeV.This unit is only used in nuclear and atomic physics, and is used to measure the energy that is necessary for the transfer of particles between two points in an electrostatic field.On the condition that the potential difference between these points is equal to 1 volt.
Hence, given that 1 amu= 931.494829533852 MeV proton mass is about
mp = 938 MeV.
This conclusion was obtained on the basis of mass-spectroscopic measurements, and it is a lot in the form in which it is shown above, it is also called and e nergiey proton rest .
Thus, focusing on the needs of the experiment, the mass of the smallest particles can be expressed in three different values in three different units.
In addition, the proton mass can be expressed relative to the mass of the electron, which is known to be much "harder" positively charged particles.Equals mass at roughly and significant errors in this case will 1836.152 672 relative to the weight of the electron.