The questions “What is matter made of?”, “What is the nature of matter?” has always occupied mankind. Since ancient times, philosophers and scientists have been looking for answers to these questions, creating both realistic and completely amazing and fantastic theories and hypotheses. However, just a century ago, mankind came as close as possible to unraveling this mystery by discovering the atomic structure of matter. But what is the composition of the nucleus of an atom? What does everything consist of?
From theory to reality
By the beginning of the twentieth century, atomic structure had ceased to be just a hypothesis, but had become an absolute fact. It turned out that the composition of the nucleus of an atom is a very complex concept. It includes But the question arose: the composition of the atom and include different amount these charges or not?
planetary model
Initially, they imagined that the atom was built very similar to ours. solar system. However, it quickly turned out that this view was not entirely correct. The problem of a purely mechanical transfer of the astronomical scale of the picture to an area that occupies millionths of a millimeter has led to a significant and dramatic change in the properties and qualities of phenomena. The main difference was in the much more stringent laws and rules by which the atom is built.
Disadvantages of the planetary model
First, since atoms of the same kind and element must be exactly the same in terms of parameters and properties, then the orbits of the electrons of these atoms must also be the same. However, the laws of motion of astronomical bodies could not provide answers to these questions. The second contradiction lies in the fact that the motion of an electron along the orbit, if we apply to it the well-studied physical laws must necessarily be accompanied by a permanent release of energy. As a result, this process would lead to the depletion of the electron, which would eventually die out and even fall into the nucleus.
Wave structure of the mother and
In 1924, a young aristocrat, Louis de Broglie, came up with an idea that turned the scientific community around such questions as the composition of atomic nuclei. The idea was that an electron is not just a moving ball that revolves around the nucleus. This is a blurry substance that moves according to laws resembling the propagation of waves in space. Quite quickly, this idea was extended to the movement of any body as a whole, explaining that we notice only one side of this very movement, but the second is not actually manifested. We can see the propagation of waves and not notice the movement of the particle, or vice versa. In fact, both of these sides of motion always exist, and the rotation of an electron in orbit is not only the movement of the charge itself, but also the propagation of waves. This approach is fundamentally different from the previously accepted planetary model.
Elementary basis
The nucleus of an atom is the center. Electrons revolve around it. Everything else is determined by the properties of the core. It is necessary to talk about such a concept as the composition of the nucleus of an atom from the most important point - from the charge. In the composition of the atom, there is a certain one that carries a negative charge. The nucleus itself has a positive charge. From this we can draw certain conclusions:
- The nucleus is a positively charged particle.
- Around the nucleus is a pulsating atmosphere created by charges.
- It is the nucleus and its characteristics that determine the number of electrons in an atom.
Kernel Properties
Copper, glass, iron, wood have the same electrons. An atom can lose a couple of electrons or even all. If the nucleus remains positively charged, then it is able to attract the right amount of negatively charged particles from other bodies, which will allow it to survive. If an atom loses a certain number of electrons, then the positive charge on the nucleus will be greater than the remainder of the negative charges. In this case, the entire atom will acquire an excess charge, and it can be called a positive ion. In some cases, an atom can attract more electrons, and then it will become negatively charged. Therefore, it can be called a negative ion.
How much does an atom weigh ?
The mass of an atom is mainly determined by the nucleus. The electrons that make up the atom and the atomic nucleus weigh less than one thousandth of the total mass. Since mass is considered a measure of the energy reserve that a substance possesses, this fact is considered incredibly important when studying such a question as the composition of the nucleus of an atom.
Radioactivity
The most difficult questions arose after the discovery that radioactive elements emit alpha, beta, and gamma waves. But such radiation must have a source. Rutherford in 1902 showed that such a source is the atom itself, or rather, the nucleus. On the other hand, radioactivity is not only the emission of rays, but also the conversion of one element into another, with completely new chemical and physical properties. That is, radioactivity is a change in the nucleus.
What do we know about nuclear structure?
Almost a hundred years ago, the physicist Prout put forward the idea that the elements in periodic system are not incoherent forms, but are combinations. Therefore, one could expect that both the charges and the masses of the nuclei would be expressed in terms of integer and multiple charges of hydrogen itself. However, this is not quite true. Studying the properties of atomic nuclei using electromagnetic fields, the physicist Aston found that elements whose atomic weights were not integer and multiple, in fact, are a combination different atoms and not just one substance. In all cases where the atomic weight is not an integer, we observe a mixture of different isotopes. What it is? If we talk about the composition of the nucleus of an atom, isotopes are atoms with the same charges, but with different masses.
Einstein and the nucleus of the atom
The theory of relativity says that mass is not a measure by which the amount of matter is determined, but a measure of the energy that matter possesses. Accordingly, matter can be measured not by mass, but by the charge that makes up this matter, and the energy of the charge. When the same charge approaches another of the same, the energy will increase, otherwise it will decrease. This, of course, does not mean a change in matter. Accordingly, from this position, the nucleus of an atom is not a source of energy, but rather, a residue after its release. So there is some contradiction.
Neutrons
The Curies, when bombarded with alpha particles of beryllium, discovered some incomprehensible rays that, colliding with the nucleus of an atom, repel it with great force. However, they are able to pass through a large thickness of matter. This contradiction was resolved by the fact that the given particle turned out to have a neutral electric charge. Accordingly, it was called the neutron. Thanks to further research, it turned out that it is almost the same as that of the proton. Generally speaking, the neutron and the proton are incredibly similar. Taking into account this discovery, it was definitely possible to establish that both protons and neutrons are included in the composition of the nucleus of an atom, and in equal quantities. Everything gradually fell into place. The number of protons is the atomic number. Atomic weight is the sum of the masses of neutrons and protons. An isotope can also be called an element in which the number of neutrons and protons will not be equal to each other. As mentioned above, in such a case, although the element remains essentially the same, its properties may change significantly.
The nucleus of an atom is made up of nucleons, which are subdivided into protons and neutrons.
Symbolic designation of the nucleus of an atom:
A is the number of nucleons, i.e. protons + neutrons (or atomic mass)
Z is the number of protons (equal to the number of electrons)
N is the number of neutrons (or atomic number)
NUCLEAR FORCES
They act between all nucleons in the nucleus;
- forces of attraction;
- short-range
Nucleons are attracted to each other by nuclear forces, which are completely different from either gravitational or electrostatic forces. . Nuclear forces fall off very quickly with distance. The radius of their action is about 0.000 000 000 000 001 meters.
For this ultra-small length, which characterizes the size of atomic nuclei, a special designation was introduced - 1 Fm (in honor of the Italian physicist E. Fermi, 1901-1954). All nuclei are several fermi in size. The radius of nuclear forces is equal to the size of a nucleon, therefore nuclei are clots of very dense matter. Perhaps the densest in terrestrial conditions.
Nuclear forces are strong interactions. They are many times greater than the Coulomb force (at the same distance). Short-range limits the action of nuclear forces. With an increase in the number of nucleons, the nuclei become unstable, and therefore most heavy nuclei are radioactive, and very heavy ones cannot exist at all.
The finite number of elements in nature is a consequence of the short range of nuclear forces.
The structure of the atom - Cool! Physics
Did you know?
In the middle of the 20th century, nuclear theory predicted the existence of stable elements with serial numbers Z = 110 -114.
In Dubna, the 114th element was obtained with an atomic mass of A = 289, which "lived" for only 30 seconds, which is incredibly long for an atom with a nucleus of this size.
Today, theorists are already discussing the properties of superheavy nuclei with a mass of 300 and even 500.
Atoms with the same atomic number are called isotopes: in the periodic table
they are located in one cell (in Greek isos - equal, topos - place).
The chemical properties of isotopes are almost identical.
If there are about 100 elements in nature, then there are more than 2000 isotopes. Many of them are unstable, that is, radioactive, and decay, emitting various types of radiation.
Isotopes of the same element differ in composition only by the number of neutrons in the nucleus.
Isotopes of hydrogen.
If you remove the space from all the atoms of the human body, then what remains can fit into the eye of a needle.
inquisitive
"Gliding" cars
If, while driving a car on a wet road at high speed, you brake sharply, then the car will behave like a glider; its tires will begin to slide on a thin film of water, practically without touching the road. Why is this happening? Why doesn't a car always slide on wet roads even when the brakes are off? Is there a tread pattern that reduces this effect?
Turns out...
Several tread patterns have been proposed to reduce the chance of "hydroplaning". For example, the groove may lead water to the rear contact point of the tread with the road, from where the water will be thrown out. On other, smaller grooves, water can be discharged to the sides. Finally, small grooves on the tread can "wet" the water layer on the road, touching it just before the main contact zone of the tread with the road surface. In all cases, the goal is to remove water from the contact zone as soon as possible and prevent hydroplaning.
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atomic nucleus- This central part an atom, made up of protons and neutrons (collectively called nucleons).
The nucleus was discovered by E. Rutherford in 1911 while studying the passage α -particles through matter. It turned out that almost the entire mass of an atom (99.95%) is concentrated in the nucleus. The size of the atomic nucleus is of the order of 10 -1 3 -10 - 12 cm, which is 10,000 times smaller than the size electron shell.
The planetary model of the atom proposed by E. Rutherford and his experimental observation of hydrogen nuclei knocked out α -particles from the nuclei of other elements (1919-1920), led the scientist to the idea of proton. The term proton was introduced in the early 20s of the XX century.
Proton (from Greek. protons- first, symbol p) is stable elementary particle, the nucleus of an atom of hydrogen.
Proton is a positively charged particle whose charge is absolute value equal to the charge of an electron e\u003d 1.6 10 -1 9 Cl. Mass of a proton in 1836 times more mass electron. Rest mass of a proton m p= 1.6726231 10 -27 kg = 1.007276470 amu
The second particle in the nucleus is neutron.
Neutron (from lat. neuter- neither one nor the other, a symbol n) is an elementary particle that has no charge, i.e., neutral.
The mass of the neutron is 1839 times the mass of the electron. The mass of a neutron is almost equal to (slightly larger than) that of a proton: the rest mass of a free neutron m n= 1.6749286 10 -27 kg = 1.0008664902 amu and exceeds the proton mass by 2.5 electron masses. Neutron, along with the proton under the common name nucleon is part of the atomic nucleus.
The neutron was discovered in 1932 by D. Chadwig, a student of E. Rutherford, during the bombardment of beryllium α -particles. The resulting radiation with high penetrating power (it overcame an obstacle made of a lead plate 10–20 cm thick) intensified its effect when passing through the paraffin plate (see figure). The estimation of the energy of these particles from the tracks in the cloud chamber made by the Joliot-Curies and additional observations made it possible to exclude the initial assumption that this γ -quanta. The great penetrating power of new particles, called neutrons, was explained by their electrical neutrality. After all, charged particles actively interact with matter and quickly lose their energy. The existence of neutrons was predicted by E. Rutherford 10 years before the experiments of D. Chadwig. On hit α -particles in the nuclei of beryllium, the following reaction occurs:
Here is the symbol of the neutron; its charge is equal to zero, and the relative atomic mass is approximately equal to one. A neutron is an unstable particle: a free neutron in a time of ~ 15 min. decays into a proton, an electron and a neutrino - a particle devoid of rest mass.
After the discovery of the neutron by J. Chadwick in 1932, D. Ivanenko and W. Heisenberg independently proposed proton-neutron (nucleon) model of the nucleus. According to this model, the nucleus consists of protons and neutrons. Number of protons Z coincides with the serial number of the element in the table of D. I. Mendeleev.
Core charge Q determined by the number of protons Z, which are part of the nucleus, and is a multiple of the absolute value of the electron charge e:
Q = + Ze.
Number Z called nuclear charge number or atomic number.
Mass number of the nucleus BUT called the total number of nucleons, i.e., protons and neutrons contained in it. The number of neutrons in a nucleus is denoted by the letter N. So the mass number is:
A = Z + N.
The nucleons (proton and neutron) are assigned a mass number equal to one, and the electron is assigned a zero value.
The idea of the composition of the nucleus was also facilitated by the discovery isotopes.
Isotopes (from the Greek. isos equal, same and topoa- place) - these are varieties of atoms of the same chemical element, the atomic nuclei of which have the same number of protons ( Z) and a different number of neutrons ( N).
The nuclei of such atoms are also called isotopes. Isotopes are nuclides one element. Nuclide (from lat. nucleus- nucleus) - any atomic nucleus (respectively, an atom) with given numbers Z and N. The general designation of nuclides is ……. where X- symbol of a chemical element, A=Z+N- mass number.
Isotopes occupy the same place in the Periodic Table of the Elements, hence their name. As a rule, isotopes differ significantly in their nuclear properties (for example, in their ability to enter into nuclear reactions). The chemical (and almost equally physical) properties of isotopes are the same. This is explained by Chemical properties element are determined by the charge of the nucleus, since it is he who affects the structure of the electron shell of the atom.
The exception is isotopes of light elements. Isotopes of hydrogen 1 H — protium, 2 H— deuterium, 3 H — tritium they differ so much in mass that their physical and chemical properties are different. Deuterium is stable (i.e., not radioactive) and is included as a small impurity (1: 4500) in ordinary hydrogen. Deuterium combines with oxygen to form heavy water. It boils at normal atmospheric pressure at 101.2°C and freezes at +3.8°C. Tritium β is radioactive with a half-life of about 12 years.
All chemical elements have isotopes. Some elements have only unstable (radioactive) isotopes. For all elements, radioactive isotopes have been artificially obtained.
Isotopes of uranium. The element uranium has two isotopes - with mass numbers 235 and 238. The isotope is only 1/140 of the more common.
As already noted, an atom consists of three types of elementary particles: protons, neutrons and electrons. The atomic nucleus is the central part of the atom, consisting of protons and neutrons. Protons and neutrons have the common name nucleon, in the nucleus they can turn into each other. The nucleus of the simplest atom, the hydrogen atom, consists of one elementary particle, the proton.
The diameter of the nucleus of an atom is approximately 10 -13 - 10 -12 cm and is 0.0001 of the diameter of an atom. However, almost the entire mass of an atom (99.95 - 99.98%) is concentrated in the nucleus. If it were possible to obtain 1 cm 3 of pure nuclear matter, its mass would be 100 - 200 million tons. The mass of the nucleus of an atom is several thousand times greater than the mass of all the electrons that make up the atom.
Proton- an elementary particle, the nucleus of a hydrogen atom. The mass of a proton is 1.6721x10 -27 kg, it is 1836 times the mass of an electron. The electric charge is positive and equal to 1.66x10 -19 C. A pendant is a unit of electric charge equal to the amount of electricity passing through the cross section of a conductor in a time of 1s at a constant current strength of 1A (amperes).
Each atom of any element contains a certain number of protons in the nucleus. This number is constant for a given element and determines its physical and chemical properties. That is, it depends on the number of protons with which chemical element we're dealing. For example, if one proton in the nucleus is hydrogen, if 26 protons are iron. The number of protons in an atomic nucleus determines the charge of the nucleus (charge number Z) and serial number element in the periodic system of elements D.I. Mendeleev (atomic number of the element).
Hneutron- an electrically neutral particle with a mass of 1.6749 x10 -27 kg, 1839 times the mass of an electron. A neuron in a free state is an unstable particle; it independently turns into a proton with the emission of an electron and an antineutrino. The half-life of neutrons (the time during which half of the original number of neutrons decays) is approximately 12 minutes. However, in a bound state inside stable atomic nuclei, it is stable. The total number of nucleons (protons and neutrons) in the nucleus is called the mass number (atomic mass - A). The number of neutrons that make up the nucleus is equal to the difference between the mass and charge numbers: N = A - Z.
Electron- an elementary particle, the carrier of the smallest mass - 0.91095x10 -27 g and the smallest electric charge - 1.6021x10 -19 C. This is a negatively charged particle. The number of electrons in an atom is equal to the number of protons in the nucleus, i.e. the atom is electrically neutral.
Positron– an elementary particle with a positive electric charge, an antiparticle with respect to an electron. The mass of an electron and a positron are equal, and the electric charges are equal in absolute value, but opposite in sign.
Different types of nuclei are called nuclides. A nuclide is a type of atom with a given number of protons and neutrons. In nature, there are atoms of the same element with different atomic masses (mass numbers): 17 35 Cl, 17 37 Cl, etc. The nuclei of these atoms contain the same number of protons, but a different number of neutrons. Varieties of atoms of the same element that have the same nuclear charge but different mass numbers are called isotopes . Having the same number of protons, but differing in the number of neutrons, isotopes have the same structure of electron shells, i.e. very similar chemical properties and occupy the same place in the periodic table of chemical elements.
Isotopes are denoted by the symbol of the corresponding chemical element with the index A located at the top left - the mass number, sometimes the number of protons (Z) is also given at the bottom left. For example, the radioactive isotopes of phosphorus are 32 P, 33 P, or 15 32 P and 15 33 P, respectively. When designating an isotope without indicating the symbol of the element, the mass number is given after the designation of the element, for example, phosphorus - 32, phosphorus - 33.
Most chemical elements have several isotopes. In addition to the hydrogen isotope 1 H-protium, heavy hydrogen 2 H-deuterium and superheavy hydrogen 3 H-tritium are known. Uranium has 11 isotopes, in natural compounds there are three of them (uranium 238, uranium 235, uranium 233). They have 92 protons and 146.143 and 141 neutrons, respectively.
Currently, more than 1900 isotopes of 108 chemical elements are known. Of these, natural isotopes include all stable (there are approximately 280 of them) and natural isotopes that are part of radioactive families (there are 46 of them). The rest are artificial, they are obtained artificially as a result of various nuclear reactions.
The term "isotopes" should only be used when referring to atoms of the same element, for example, carbon isotopes 12 C and 14 C. If atoms of different chemical elements are meant, it is recommended to use the term "nuclides", for example, radionuclides 90 Sr, 131 J, 137 Cs.
