How many elementary particles are there in the Universe? The structure of atoms, electron orbits, the maximum number of electrons in orbits, geochemical families. The dependence of the properties of elements on the structure of electron shells and mass in the view of modern science

Composition of the nucleus of an atom. Calculation of protons and neutrons

According to modern concepts, an atom consists of a nucleus and electrons located around it. The nucleus of an atom, in turn, consists of smaller elementary particles - a certain number protons and neutrons(the generally accepted name for which is nucleons), interconnected by nuclear forces.

Number of protons in the nucleus determines the structure of the electron shell of the atom. And the electron shell determines the physical and chemical properties of a substance. The number of protons corresponds to the serial number of an atom in Mendeleev’s periodic system of chemical elements, also called charge number, atomic number, atomic number. For example, the number of protons in a Helium atom is 2. In the periodic table it is number 2 and is designated as He 2. The symbol for the number of protons is the Latin letter Z. When writing formulas, often the number indicating the number of protons is located below the symbol of the element or right or left: He 2 / 2 He.

Number of neutrons corresponds to a specific isotope of an element. Isotopes are elements with the same atomic number (same number of protons and electrons) but different mass numbers. Mass number– the total number of neutrons and protons in the nucleus of an atom (denoted by the Latin letter A). When writing formulas, the mass number is indicated at the top of the element symbol on one side: He 4 2 / 4 2 He (Helium isotope - Helium - 4)

Thus, to find out the number of neutrons in a particular isotope, the number of protons should be subtracted from the total mass number. For example, we know that the Helium-4 He 4 2 atom contains 4 elementary particles, since the mass number of the isotope is 4. Moreover, we know that He 4 2 has 2 protons. Subtracting from 4 (total mass number) 2 (number of protons) we get 2 - the number of neutrons in the Helium-4 nucleus.

THE PROCESS OF CALCULATING THE NUMBER OF PHANTOM PARTICLES IN THE ATOMIC NUCLEUS. As an example, it was not by chance that we considered Helium-4 (He 4 2), the nucleus of which consists of two protons and two neutrons. Since the Helium-4 nucleus, called the alpha particle (α particle), is the most efficient in nuclear reactions, it is often used for experiments in this direction. It is worth noting that in formulas for nuclear reactions the symbol α is often used instead of He 4 2.

It was with the participation of alpha particles that E. Rutherford carried out the first nuclear transformation reaction in the official history of physics. During the reaction, alpha particles (He 4 2) “bombarded” the nuclei of the nitrogen isotope (N 14 7), resulting in the formation of an oxygen isotope (O 17 8) and one proton (p 1 1)

This nuclear reaction looks like this:

Let's calculate the number of phantom Po particles before and after this transformation.

TO CALCULATE THE NUMBER OF PHANTOM PARTICLES YOU NEED:
Step 1. Count the number of neutrons and protons in each nucleus:
- the number of protons is indicated in the lower indicator;
- we find out the number of neutrons by subtracting the number of protons (lower indicator) from the total mass number (upper indicator).

Step 2. Count the number of phantom Po particles in the atomic nucleus:
- multiply the number of protons by the number of phantom Po particles contained in 1 proton;
- multiply the number of neutrons by the number of phantom Po particles contained in 1 neutron;

Step 3. Add up the number of phantom Po particles:
- add the resulting number of phantom Po particles in protons with the resulting number in neutrons in nuclei before the reaction;
- add the resulting number of phantom Po particles in protons with the resulting number in neutrons in nuclei after the reaction;
- compare the number of phantom Po particles before the reaction with the number of phantom Po particles after the reaction.

AN EXAMPLE OF DEVELOPED CALCULATION OF THE NUMBER OF PHANTOM PARTICLES IN ATOMIC NUCLEI.
(Nuclear reaction involving an α particle (He 4 2), carried out by E. Rutherford in 1919)

BEFORE THE REACTION (N 14 7 + He 4 2)
N 14 7

Number of protons: 7
Number of neutrons: 14-7 = 7
in 1 proton – 12 Po, which means in 7 protons: (12 x 7) = 84;
in 1 neutron – 33 Po, which means in 7 neutrons: (33 x 7) = 231;
Total number of phantom Po particles in the nucleus: 84+231 = 315

He 4 2
Number of protons – 2
Number of neutrons 4-2 = 2
Number of phantom Po particles:
in 1 proton – 12 Po, which means in 2 protons: (12 x 2) = 24
in 1 neutron – 33 Po, which means in 2 neutrons: (33 x 2) = 66
Total number of phantom Po particles in the nucleus: 24+66 = 90

Total number of phantom Po particles before the reaction

N 14 7 + He 4 2
315 + 90 = 405

AFTER THE REACTION (O 17 8) and one proton (p 1 1):
O 17 8
Number of protons: 8
Number of neutrons: 17-8 = 9
Number of phantom Po particles:
in 1 proton – 12 Po, which means in 8 protons: (12 x 8) = 96
in 1 neutron – 33 Po, which means in 9 neutrons: (9 x 33) = 297
Total number of phantom Po particles in the nucleus: 96+297 = 393

p 1 1
Number of protons: 1
Number of neutrons: 1-1=0
Number of phantom Po particles:
There are 12 Po in 1 proton
There are no neutrons.
Total number of phantom Po particles in the nucleus: 12

Total number of phantom Po particles after the reaction
(O 17 8 + p 1 1):
393 + 12 = 405

Let's compare the number of phantom Po particles before and after the reaction:

AN EXAMPLE OF A SHORT FORM FOR CALCULATING THE NUMBER OF PHANTOM PARTICLES IN A NUCLEAR REACTION.

A well-known nuclear reaction is the reaction of interaction of α-particles with a beryllium isotope, in which a neutron was first discovered, manifesting itself as an independent particle as a result of nuclear transformation. This reaction was carried out in 1932 by the English physicist James Chadwick. Reaction formula:

213 + 90 → 270 + 33 - the number of phantom Po particles in each of the nuclei

303 = 303 - the total sum of phantom Po particles before and after the reaction

The numbers of phantom Po particles before and after the reaction are equal.

For a long time, many properties of matter remained a secret for researchers. Why do some substances conduct electricity well, while others do not? Why does iron gradually deteriorate under the influence of the atmosphere, while noble metals are perfectly preserved for thousands of years? Many of these questions found an answer after man became aware of the structure of the atom: its structure, the number of electrons in each electronic layer. Moreover, mastering even the very basics of the structure of atomic nuclei opened a new era for the world.

What elements are the elementary building blocks of matter made of, how do they interact with each other, what can we learn to use from this?

in the view of modern science

Currently, most scientists tend to adhere to the planetary model of the structure of matter. According to this model, at the center of each atom there is a nucleus, tiny even in comparison with the atom (it is tens of thousands of times smaller than the whole atom). But the same cannot be said about the mass of the nucleus. Almost all the mass of an atom is concentrated in the nucleus. The nucleus is positively charged.

Electrons rotate around the nucleus in various orbits, not circular, as is the case with the planets of the Solar System, but volumetric (spheres and volumetric eights). The number of electrons in an atom is numerically equal to the charge of the nucleus. But it is very difficult to consider an electron as a particle that moves along some trajectory.

Its orbit is tiny, and its speed is almost like that of a light beam, so it is more correct to consider the electron together with its orbit as a kind of negatively charged sphere.

Members of the atomic family

All atoms are made up of 3 constituent elements: protons, electrons and neutrons.

Proton is the main building material of the nucleus. Its weight is equal to an atomic unit (mass of a hydrogen atom) or 1.67 ∙ 10 -27 kg in the SI system. The particle is positively charged, and its charge is taken as unity in the system of elementary electric charges.

The neutron is the proton's twin in mass, but is not charged in any way.

The above two particles are called nuclides.

An electron is the opposite of a proton in charge (the elementary charge is −1). But the electron let us down in terms of weight, its mass is only 9.12 ∙ 10 -31 kg, which is almost 2 thousand times lighter than a proton or neutron.

How did they “spot” it?

How could one discern the structure of an atom if even the most modern technical means do not allow, and in the near future will not allow, obtaining images of the particles that make it up? How did scientists know the number of protons, neutrons and electrons in the nucleus and their location?

The assumption about the planetary structure of atoms was made on the basis of the results of bombarding thin metal foil with various particles. The figure clearly shows how various elementary particles interact with matter.

The number of electrons passing through the metal in the experiments was zero. This is explained simply: negatively charged electrons are repelled from the electron shells of the metal, which also have a negative charge.

A beam of protons (charge +) passed through the foil, but with “losses”. Some were repelled by the nuclei that got in the way (the probability of such hits is very insignificant), some deviated from the original trajectory, flying too close to one of the nuclei.

Neutrons became the most “effective” in terms of breaking through metal. A neutrally charged particle was lost only in the event of a direct collision with the nucleus of a substance, while 99.99% of neutrons safely passed through the thickness of the metal. By the way, it was possible to calculate the size of the nuclei of certain chemical elements based on the number of neutrons at the input and output.

Based on the data obtained, the currently dominant theory of the structure of matter was built, which successfully explains most issues.

What and how much

The number of electrons in an atom depends on the atomic number. Thus, an ordinary hydrogen atom has only one proton. A single electron is circling around in orbit. The next element of the periodic table, helium, is a little more complicated. Its nucleus consists of two protons and two neutrons and thus has an atomic mass of 4.

As the atomic number increases, the size and mass of the atom increase. The serial number of a chemical element in the periodic table corresponds to the charge of the nucleus (the number of protons in it). The number of electrons in an atom is equal to the number of protons. Thus, a lead atom (serial number 82) has 82 protons in its nucleus. There are 82 electrons in orbit around the nucleus. To calculate the number of neutrons in a nucleus, it is enough to subtract the number of protons from the atomic mass:

Why are there always equal numbers of them?

Any system in our Universe strives for stability. When applied to an atom, this is expressed in its neutrality. If you imagine for a second that all atoms in the Universe, without exception, have one or another charge of different sizes with different signs, you can imagine what kind of chaos would ensue in the world.

But since the number of protons and electrons in an atom is equal, the final charge of each “brick” is zero.

The number of neutrons in an atom is an independent quantity. Moreover, atoms of the same chemical element can have different numbers of these particles with zero charge. Example:

• 1 proton + 1 electron + 0 neutrons = hydrogen (atomic mass 1);
• 1 proton + 1 electron + 1 neutron = deuterium (atomic mass 2);
• 1 proton + 1 electron + 2 neutrons = tritium (atomic mass 3).

In this case, the number of electrons in the atom does not change, the atom remains neutral, and its mass changes. Such variations of chemical elements are usually called isotopes.

Is an atom always neutral?

No, the number of electrons in an atom is not always equal to the number of protons. If an electron or two could not be temporarily “taken away” from an atom, there would be no such thing as galvanism. An atom, like any matter, can be influenced.

Under the influence of a sufficiently strong electric field, one or more electrons can “fly away” from the outer layer of an atom. In this case, the particle of the substance ceases to be neutral and is called an ion. It can move in a gas or liquid environment, transferring electrical charge from one electrode to another. In this way, electric charge is stored in batteries, and thin films of some metals are applied to the surfaces of others (gold-plating, silver-plating, chrome-plating, nickel-plating, etc.).

The number of electrons is also unstable in metals - conductors of electric current. The electrons of the outer layers seem to wander from atom to atom, transferring electrical energy along the conductor.

To the question How to calculate the number of electrons in orbits (or as they are called in Russian) asked by the author LITTLE Sober-and-Evil! the best answer is The maximum number of electrons in 1 orbital (electron cloud) is 2. Orbitals that are close in size and energy form sublevels, the maximum number of electrons on them: s-sublevel - 2, p-sublevel - 6, d-sublevel - 10, f-sublevel - 14 (orbitals at the sublevel are correspondingly 2 times less). Sublevels that are close in energy form ENERGY LEVELS, or ELECTRONIC LAYERS (apparently, these are the ones you are asking about). The maximum number of electrons at energy levels: 1st - 2, 2nd - 8, 3rd - 18, 4th and further - 32. THE EXTERNAL ELECTRON LAYER OF AN ATOM CANNOT BE MORE THAN 8 ELECTRONS.
The total number of electrons in all electron layers is equal to the charge of the nucleus (the atomic number of the element). The number of electronic layers of an atom is equal to the number of the period in which this element is located. Filling of a new electron layer begins after the s- and p-orbitals on the previous layer are filled.
The d-orbitals of the previous layer are filled after the s-orbitals of the next layer are filled, and after these d-orbitals the outer p-sublevel is filled. f-orbitals are filled only in lanthanides and actinides (2 rows of 14 elements at the bottom of the periodic table); the f-sublevel of the third outside electron layer is filled after the s-sublevel of the outer layer (2 electrons) and 1 electron in the d-sublevel of the previous layer are filled. After filling the third outside f-sublevel, the filling of the second outside d-sublevel (inserted decade) continues, and then the p-sublevel of the outer layer is filled.
For example, vanadium V is element 5 of group 4 of period. It has 1 (2 electrons) and 2 (8 electrons) levels filled, at the 3rd level - s- and p-sublevels (i.e. 8 electrons), then the s-sublevel is filled with 4 layers (2 electrons), and then - d-sublevel 3 layers (3 electrons), i.e. on the 3rd layer - 8 + 3 = 11 electrons, and the electronic diagram of the atom: V +23)2)8)11)2. + 23 is the charge of the nucleus (ordinal number; 2 + 8 + 11 + 2 = 23 - the number of electrons is equal to the ordinal number (this is a check). How to find out the number of d-electrons: each period begins with 2 elements whose outer s-sublevel is filled (in the 4th period these are K and Ca - elements of groups 1 and 2), then for 10 elements (inserted decade) the previous d-sublevel is filled - 1 electron each (in the 4th period - from Sc to Zn). Consider: vanadium is in). side subgroup (i.e. d-element), this is the 5th element of the 4th period, it has 5 - 2 = 3 d-electrons on the previous (third) layer (i.e. it is the third in the inserted decade).
For elements of the side subgroups of groups 1 and 6, a “leap” of 1 outer s-electron to the previous d-sublevel is observed: an energetically more favorable state arises when the d-sublevel is filled completely or half. For example, copper Cu instead of...3d9 4s2 will have an electronic configuration...3d10 4s1.

An atom of a chemical element consists of a nucleus and electrons. Quantity electrons in an atom depends on its atomic number. The electronic configuration determines the distribution of the electron across shells and subshells.

You will need

• Atomic number, molecule composition

Instructions

If the atom is electrically neutral, then the number electrons it is equal to the number of protons. The number of protons corresponds to the atomic number of the element in the periodic table. For example, hydrogen has the first atomic number, so its atom has one electron. The atomic number of sodium is 11, so the sodium atom has 11 electrons.

An atom can also lose or gain electrons. In this case, the atom becomes an ion, which has an electrical positive or negative charge. Let's say one of electrons sodium has left the electron shell of the atom. The sodium atom will then become a positively charged ion, having a charge of +1 and 10 electrons on its electronic shell. Upon joining electrons the atom becomes a negative ion.

Atoms of chemical elements can also combine to form molecules, the smallest particle of matter. Quantity electrons in a molecule is equal to the amount electrons all the atoms it contains. For example, the water molecule H2O consists of two hydrogen atoms, each of which has one electron, and an oxygen atom, which has 8 electrons. That is, there are only 10 in a water molecule electrons.

Until the beginning of the 20th century, scientists believed that an atom was the smallest indivisible particle of matter, but this turned out to be wrong. In fact, at the center of the atom is its nucleus with positively charged protons and neutral neutrons, and negatively charged electrons rotate in orbitals around the nucleus (this model of the atom was proposed in 1911 by E. Rutherford). It is noteworthy that the masses of protons and neutrons are almost equal, but the mass of an electron is about 2000 times less.

Although an atom contains both positively and negatively charged particles, its charge is neutral, because an atom has the same number of protons and electrons, and differently charged particles neutralize each other.

Later, scientists found out that electrons and protons have the same amount of charge, equal to 1.6 10 -19 C (C is a coulomb, a unit of electric charge in the SI system.

Have you ever thought about the question - what number of electrons corresponds to a charge of 1 C?

1/(1.6·10 -19) = 6.25·10 18 electrons

Electric power

Electric charges influence each other, which manifests itself in the form electric force.

If a body has an excess of electrons, it will have a total negative electrical charge, and vice versa - if there is a deficiency of electrons, the body will have a total positive charge.

By analogy with magnetic forces, when like-charged poles repel and oppositely charged poles attract, electric charges behave in a similar way. However, in physics it is not enough to simply talk about the polarity of an electric charge; its numerical value is important.

To find out the magnitude of the force acting between charged bodies, it is necessary to know not only the magnitude of the charges, but also the distance between them. The force of universal gravitation has already been considered previously: F = (Gm 1 m 2)/R 2

• m 1, m 2- masses of bodies;
• R- the distance between the centers of the bodies;
• G = 6.67 10 -11 Nm 2 /kg- universal gravitational constant.

As a result of laboratory experiments, physicists derived a similar formula for the force of interaction of electric charges, which was called Coulomb's law:

F = kq 1 q 2 /r 2

• q 1, q 2 - interacting charges, measured in C;
• r is the distance between charges;
• k - proportionality coefficient ( SI: k=8.99·10 9 Nm 2 Cl 2; SSSE: k=1).

• k=1/(4πε 0).
• ε 0 ≈8.85·10 -12 C 2 N -1 m -2 - electrical constant.

According to Coulomb's law, if two charges have the same sign, then the force F acting between them is positive (the charges repel each other); if the charges have opposite signs, the acting force is negative (charges attract each other).

How enormous the force of a charge of 1 C is can be judged using Coulomb's law. For example, if we assume that two charges, each 1 C, are spaced at a distance of 10 meters from each other, then they will repel each other with force:

F = kq 1 q 2 /r 2 F = (8.99 10 9) 1 1/(10 2) = -8.99 10 7 N

This is a fairly large force, roughly comparable to a mass of 5600 tons.

Let's now use Coulomb's law to find out at what linear speed the electron rotates in a hydrogen atom, assuming that it moves in a circular orbit.

According to Coulomb's law, the electrostatic force acting on an electron can be equated to the centripetal force:

F = kq 1 q 2 /r 2 = mv 2 /r

Taking into account the fact that the mass of the electron is 9.1·10 -31 kg, and the radius of its orbit = 5.29·10 -11 m, we obtain the value 8.22·10 -8 N.

Now we can find the linear speed of the electron:

8.22·10 -8 = (9.1·10 -31)v 2 /(5.29·10 -11) v = 2.19·10 6 m/s

Thus, the electron of the hydrogen atom rotates around its center at a speed of approximately 7.88 million km/h.