An atom is the smallest particle of a chemical element that retains all of its Chemical properties. An atom consists of a positively charged nucleus and negatively charged electrons. The charge of the nucleus of any chemical element is equal to the product of Z and e, where Z is the serial number given element in the periodic system chemical elements, e - the value of the elementary electric charge.
Electron- This smallest particle substances with a negative electric charge e=1.6·10 -19 coulombs, taken as an elementary electric charge. Electrons, rotating around the nucleus, are located on the electron shells K, L, M, etc. K is the shell closest to the nucleus. The size of an atom is determined by the size of its electron shell. An atom can lose electrons and become positive ion or gain electrons and become a negative ion. The charge of an ion determines the number of electrons lost or gained. The process of turning a neutral atom into a charged ion is called ionization.
atomic nucleus (central part atom) consists of elementary nuclear particles - protons and neutrons. The radius of the nucleus is about a hundred thousand times smaller than the radius of the atom. The density of the atomic nucleus is extremely high. Protons- These are stable elementary particles having a unit positive electric charge and a mass 1836 times greater than the mass of an electron. The proton is the nucleus of the lightest element, hydrogen. The number of protons in the nucleus is Z. Neutron is a neutral (not having an electric charge) elementary particle with a mass very close to the mass of a proton. Since the mass of the nucleus is the sum of the mass of protons and neutrons, the number of neutrons in the nucleus of an atom is A - Z, where A is the mass number of a given isotope (see). The proton and neutron that make up the nucleus are called nucleons. In the nucleus, nucleons are bound by special nuclear forces.
The atomic nucleus has a huge store of energy, which is released during nuclear reactions. Nuclear reactions occur when atomic nuclei interact with elementary particles or with the nuclei of other elements. As a result of nuclear reactions, new nuclei are formed. For example, a neutron can transform into a proton. In this case, a beta particle, i.e., an electron, is ejected from the nucleus.
The transition in the nucleus of a proton into a neutron can be carried out in two ways: either a particle with a mass equal to the mass of an electron, but with a positive charge, called a positron (positron decay), is emitted from the nucleus, or the nucleus captures one of the electrons from the nearest K-shell (K -capture).
Sometimes the formed nucleus has an excess of energy (it is in an excited state) and, passing into the normal state, releases excess energy in the form of electromagnetic radiation with a very short wavelength -. The energy released during nuclear reactions is practically used in various industries.
An atom (Greek atomos - indivisible) is the smallest particle of a chemical element that has its chemical properties. Each element is made up of certain types of atoms. The structure of an atom includes the kernel carrying a positive electric charge, and negatively charged electrons (see), forming its electronic shells. The value of the electric charge of the nucleus is equal to Z-e, where e is the elementary electric charge, equal in magnitude to the charge of the electron (4.8 10 -10 e.-st. units), and Z is the atomic number of this element in the periodic system of chemical elements (see .). Since a non-ionized atom is neutral, the number of electrons included in it is also equal to Z. The composition of the nucleus (see. Atomic nucleus) includes nucleons, elementary particles with a mass approximately 1840 times greater than the mass of an electron (equal to 9.1 10 - 28 g), protons (see), positively charged, and chargeless neutrons (see). The number of nucleons in the nucleus is called the mass number and is denoted by the letter A. The number of protons in the nucleus, equal to Z, determines the number of electrons entering the atom, the structure of the electron shells and the chemical properties of the atom. The number of neutrons in the nucleus is A-Z. Isotopes are called varieties of the same element, the atoms of which differ from each other in mass number A, but have the same Z. Thus, in the nuclei of atoms of different isotopes of one element there are a different number of neutrons at the same number protons. When designating isotopes, the mass number A is written at the top of the element symbol, and the atomic number at the bottom; for example, isotopes of oxygen are denoted: 
The dimensions of an atom are determined by the dimensions of the electron shells and for all Z are about 10 -8 cm. Since the mass of all the electrons of the atom is several thousand times less than the mass of the nucleus, the mass of the atom is proportional to the mass number. Relative mass an atom of a given isotope is determined in relation to the mass of an atom of the carbon isotope C 12, taken as 12 units, and is called the isotopic mass. It turns out to be close to the mass number of the corresponding isotope. The relative weight of an atom of a chemical element is the average (taking into account the relative abundance of the isotopes of a given element) value of the isotopic weight and is called the atomic weight (mass).
An atom is a microscopic system, and its structure and properties can only be explained with the help of quantum theory, created mainly in the 20s of the 20th century and intended to describe phenomena on an atomic scale. Experiments have shown that microparticles - electrons, protons, atoms, etc. - in addition to corpuscular ones, have wave properties that manifest themselves in diffraction and interference. In quantum theory, a certain wave field characterized by a wave function (Ψ-function) is used to describe the state of micro-objects. This function determines the probabilities of possible states of a micro-object, i.e., it characterizes the potential possibilities for the manifestation of one or another of its properties. The law of variation of the function Ψ in space and time (the Schrödinger equation), which makes it possible to find this function, plays the same role in quantum theory as in classical mechanics Newton's laws of motion. The solution of the Schrödinger equation in many cases leads to discrete possible states systems. So, for example, in the case of an atom, a series of wave functions for electrons is obtained corresponding to different (quantized) energy values. The system of energy levels of the atom, calculated by the methods of quantum theory, has received brilliant confirmation in spectroscopy. The transition of an atom from the ground state corresponding to the lowest energy level E 0 to any of the excited states E i occurs when a certain portion of energy E i - E 0 is absorbed. An excited atom goes into a less excited or ground state, usually with the emission of a photon. In this case, the photon energy hv is equal to the difference between the energies of an atom in two states: hv= E i - E k where h is Planck's constant (6.62·10 -27 erg·sec), v is the frequency of light.
In addition to atomic spectra, quantum theory allowed to explain other properties of atoms. In particular, the valency, nature chemical bond and the structure of molecules, the theory of the periodic system of elements was created.
Until the beginning of the 20th century, scientists considered the atom to be the smallest indivisible particle of matter, but this turned out not to be the case. In fact, its nucleus with positively charged protons and neutral neutrons is located in the center of the atom, negatively charged electrons rotate around the nucleus in orbitals (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 charged particles and negatively, its charge is neutral, because the atom has the same number of protons and electrons, and differently charged particles neutralize each other.
Later, scientists found that electrons and protons have the same amount of charge, equal to 1.6 10 -19 C (C - 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) \u003d 6.25 10 18 electrons
electrical force
Electric charges act on each other, which manifests itself in the form electrical force.
If a body has an excess of electrons, it will have a total negative electric charge, and vice versa - with a deficit 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 talk simply about the polarity of the 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: F = (Gm 1 m 2) / R 2
- m1, m2- masses of bodies;
- R- distance between the centers of bodies;
- G \u003d 6.67 10 -11 Nm 2 / kg is the universal gravitational constant.
As a result of laboratory experiments, physicists have derived a similar formula for the interaction force of electric charges, which is called Coulomb's law:
F = kq 1 q 2 /r 2
- q 1 , q 2 - interacting charges, measured in C;
- r - distance between charges;
- k - coefficient of proportionality ( SI: k=8.99 10 9 Nm 2 C 2 ; SGSE: 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 (the charges are attracted to each other).
How huge in strength is a charge of 1 C can be judged using Coulomb's law. For example, if we assume that two charges, each in 1 C, are separated by a distance of 10 meters from each other, then they will repel each other with force:
F \u003d kq 1 q 2 / r 2 F \u003d (8.99 10 9) 1 1 / (10 2) \u003d -8.99 10 7 N
This is a fairly large force, approximately comparable to a mass of 5600 tons.
Now, using Coulomb's law, let's find out with what linear speed an electron rotates in a hydrogen atom, assuming that it moves in a circular orbit.
The electrostatic force acting on an electron, according to Coulomb's law, 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 an 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 you can find the linear velocity of the electron:
8.22 10 -8 \u003d (9.1 10 -31) v 2 / (5.29 10 -11) v \u003d 2.19 10 6 m / s
Thus, the electron of the hydrogen atom rotates around its center at a speed equal to about 7.88 million km/h.
Chapter 9. Elementary charges. Electron and proton
§ 9.1. Electromagnetic mass and charge. The question of the essence of charge
In Chapter 5, we found out the mechanism of the emergence of inertia, explained what "inertial mass" is and what electrical phenomena and properties of elementary charges determine it. In Chapter 7 we did the same for the phenomenon of gravity and "gravitational mass". It turned out that both the inertia and gravity of bodies determine the geometric size elementary particles and their charge. Since the geometric size is a familiar concept, then at the heart of such fundamental phenomena as inertia and gravity, there is only one little-studied essence - “charge”. Until now, the concept of "charge" is mysterious and almost mystical. At first, scientists dealt only with macroscopic charges, i.e. charges of macroscopic bodies. At the beginning of the study of electricity in science, the concept of invisible "electric fluids" was used, the excess or deficiency of which leads to the electrification of bodies. For a long time, the debate was only about whether it was one liquid or two of them: positive and negative. Then it was found out that there are "elementary" charge carriers electrons and ionized atoms, i.e. atoms with an excess electron or a missing electron. Even later, the “most elementary” positive charge carriers, protons, were discovered. Then it turned out that there are many “elementary” particles and many of them have an electric charge, and this charge is always
is a multiple of some minimum detectable portion of the charge q 0 ≈ 1.602 10−19 C . This
portion and was called the "elementary charge." The charge determines the degree of participation of the body in electrical interactions and, in particular, electrostatic interactions. To date, there are no intelligible explanations of what an elementary charge is. Any reasoning on the topic that the charge consists of other charges (for example, quarks with fractional charge values) is not an explanation, but a scholastic “blurring” of the issue.
Let's try to think about the charges ourselves, using what we have already established earlier. Recall that the main law established for charges is Coulomb's law: the force of interaction between two charged bodies is directly proportional to the product of the magnitudes of their charges and inversely proportional to the square of the distance between them. It turns out that if we derive Coulomb's law from any specific physical mechanisms already studied, then we will thereby make a step in understanding the essence of charges. We have already said that elementary charges in terms of interaction with outside world are completely determined by their electric field: its structure and its motion. And they said that after the explanation of inertia and gravity in elementary charges, there is nothing but a moving electric field, and not left. And the electric field is nothing but perturbed states of vacuum, ether, plenum. Well, let's be consistent and try to reduce the electron and its charge to a moving field! We already guessed in Chapter 5 that the proton is exactly like the electron, except for the charge sign and geometric size. If, by reducing the electron to a moving field, we see that we can explain both the sign of the charge and the independence of the amount of particle charge on the size, then our task will be completed, at least in the first approximation.
§ 9.2. Strange currents and strange waves. flat electron
To begin with, let's consider an extremely simplified model situation (Fig. 9.1) of a ring charge moving along a circular path of radius r 0 . And let him in general
electrically neutral, i.e. its center has a charge opposite in sign. This is the so-called "flat electron". We do not claim that the real electron is exactly like this, we are only trying to understand for the time being whether it is possible to obtain an electrically neutral object equivalent to a free elementary charge in a flat, two-dimensional case. Let's try to create our charge from the bound charges of the ether (vacuum, plenum). Let, for definiteness, the charge of the ring be negative, and the movement of the ring occurs clockwise (Fig. 9.1). In this case, the current I t flows counterclockwise. Select a small
ring charge element dq and assign to it a small length dl. It is obvious that at each moment of time the element dq moves with a tangential velocity v t and normal acceleration a n . With such a movement, we can associate the total current of the element dI -
vector value. This value can be represented as a constant tangential current dI t, constantly "turning" its direction with the flow
time, i.e. accelerated. That is, having normal acceleration dI& n . Difficulty
further consideration is due to the fact that so far in physics, mainly such alternating currents have been considered, whose acceleration lay on the same straight line with the direction of the current itself. In this case, the situation is different: current perpendicular to its acceleration. And what? Does this invalidate the previously firmly established laws of physics?
Rice. 9.1. Ring current and its force effect on the test charge
Just as the elementary current itself is associated with its magnetic field (according to the Biot-Savart-Laplace law), so the electric field of induction is associated with the acceleration of the elementary current, as we have shown in previous chapters. These fields have a force action F on the external charge q (Fig. 9.1). Since the radius r 0 is finite, the actions
elementary currents of the right (according to the figure) half of the ring cannot be fully compensated by the opposite action of the elementary currents of the left half.
Thus, between the ring current I and the external test charge q must
force interaction occurs.
As a result, we have obtained that we can speculatively create an object that, on the whole, will be completely electrically neutral in construction, but contain a ring current. What is ring current in vacuum? This is the displacement current. It can be represented as a circular motion of bound negative (or vice versa - positive) vacuum charges at complete rest of the opposing charges located
V center. It can also be represented as a joint circular motion of positive and negative bound charges, but with different speeds, or along different radii, or
V different sides... In the end, no matter how we look at the situation, it will
be reduced to a rotating electric field E , closed in a circle . This creates a magnetic field b, due to the fact that currents flow and an additional, unlimited cr at ohm electric field Eind associated with the fact that these currents accelerated.
This is exactly what we observe near real elementary charges (for example, electrons)! Here is our phenomenology of the so-called "electrostatic" interaction. It does not require free charges (with fractional or some other charge values) to build an electron. Just enough bound vacuum charges! Recall that, according to modern concepts, a photon also consists of a moving electric field and is generally electrically neutral. If the photon is “bent” into a ring, then it will have a charge, since its electric field will now move not in a straight line and uniformly, but accelerated. Now it is clear how charges of different signs are formed: if the field E in the “ring model” (Fig. 9.1) is directed from the center to the periphery of the particle, then the charge is of one sign, if vice versa, then the other. If we open an electron (or a positron), we will create a photon. In reality, due to the need to preserve the moment of rotation, in order to turn a charge into a photon, you need to take two opposite charges, bring them together and get two electrically neutral photons as a result. Such a phenomenon (annihilation reaction) is indeed observed in experiments. So what is a charge? torque of the electric field! Next, we will try to deal with formulas and calculations and obtain Coulomb's law from the laws of induction applied to the case alternating current offset.
§ 9.3. Coulomb's law as a consequence of Faraday's law of induction
Let us show that in the two-dimensional (planar) approximation, the electron in the electrostatic sense is equivalent to the circular motion of the current, which is equal in magnitude to the charge current q 0 moving along the radius r 0 with a speed, equal speed light c.
To do this, we divide the total circular current I (Fig. 9.1) into elementary currents Idl, calculate dE ind, acting at the point where the test charge q, and integrate over the ring.
So, the current flowing in our case along the ring is equal to:
(9.1) I = q 0 v = q 0 c . 2 π r 0 2 π r 0
Since this current is curvilinear, that is, accelerated, then it is
variables:
I. Misyuchenko |
God's Last Secret |
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dt 2 r |
2πr |
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where a - centripetal acceleration, which is experienced by each element of the current when moving along a circle with a speed c.
Substituting the expression known from kinematics for acceleration a = c 2 , we get: r 0
q0 c2 |
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2πr |
2 π r 2 |
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It is clear that the derivative for the current element will be expressed by the formula:
dl= |
q0 c2 |
dl . |
|||||
2πr |
2 π r 2 |
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As follows from the Biot-Savart-Laplace law, each current element Idl creates an “elementary” magnetic field at the point where the test charge is located:
(9.5) dB = |
I[ dl , rr ] |
|||
From chapter 4 it is known that the alternating magnetic field of the elementary current generates an electric one:
(9.6) dE r = v r B dB r = |
μ 0 |
|||||||||
I [dl, r] |
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Now let's substitute in this expression the value of the derivative of the elementary circular current from (9.4):
dl sin(β) |
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dE = |
|||||||||||
2 π r 2 |
|||||||||||
It remains to integrate these elementary electric field strengths along the current contour, that is, over all dl that we have identified on the circle:
q0 c2 |
sin(β) |
r 2 ∫ |
sin(β) |
||||||||
E = ∫ dE = ∫ 8 π |
2 π r 2 |
dl= |
16 π 2 ε |
dl . |
|||||||
It is easy to see (Fig. 9.1) that integration over angles will give:
(9.9) ∫ |
sin(β) |
4 r 2 |
|||
dl = 2 r0 |
r 2 0 |
r 2 0 . |
Accordingly, the total value of the electric field strength of induction E ind from our curvilinear current at the point where the test charge is located will be equal.
If you are familiar with the structure of the atom, then you probably know that the atom of any element consists of three types of elementary particles: protons, electrons, neutrons. Protons combine with neutrons to form an atomic nucleus. Since the proton has a positive charge, the atomic nucleus is always positively charged. of the atomic nucleus is compensated by the cloud of other elementary particles surrounding it. The negatively charged electron is the part of the atom that stabilizes the charge of the proton. Depending on which atomic nucleus surrounds, an element can either be electrically neutral (in the case of an equal number of protons and electrons in the atom), or have a positive or negative charge (in the case of a shortage or excess of electrons, respectively). An atom of an element that carries a certain charge is called an ion.
It is important to remember that it is the number of protons that determines the properties of the elements and their position in the periodic table. D. I. Mendeleev. The neutrons in an atomic nucleus have no charge. Due to the fact that both protons are comparable and practically equal to each other, and the mass of an electron is negligible compared to them (1836 times less, the number of neutrons in the nucleus of an atom plays a very important role, namely: it determines the stability of the system and the speed of nuclei. Contents neutrons is determined by the isotope (variety) of the element.
However, due to the discrepancy between the masses of charged particles, protons and electrons have different specific charges (this value is determined by the ratio of the charge of an elementary particle to its mass). As a result, the specific charge of the proton is 9.578756(27) 107 C/kg versus -1.758820088(39) 1011 for the electron. Due to the high value of the specific charge, free protons cannot exist in liquid media: they are amenable to hydration.
The mass and charge of the proton are specific quantities that were established at the beginning of the last century. Which scientist made this - one of the greatest - discovery of the twentieth century? Back in 1913, Rutherford, based on the fact that the masses of all known chemical elements are greater than the mass of a hydrogen atom by an integer number of times, suggested that the nucleus of a hydrogen atom is included in the nucleus of an atom of any element. Somewhat later, Rutherford conducted an experiment in which he studied the interaction of the nuclei of the nitrogen atom with alpha particles. As a result of the experiment, a particle flew out of the nucleus of the atom, which Rutherford called "proton" (from the Greek word "protos" - the first) and suggested that it was the nucleus of the hydrogen atom. The assumption was proved experimentally during the re-conducting of this scientific experiment in a cloud chamber.
The same Rutherford in 1920 put forward a hypothesis about the existence in the atomic nucleus of a particle whose mass is equal to the mass of a proton, but which does not carry any electric charge. However, Rutherford himself failed to detect this particle. But in 1932, his student Chadwick experimentally proved the existence of a neutron in the atomic nucleus - a particle, as predicted by Rutherford, approximately equal in mass to a proton. It was more difficult to detect neutrons, since they do not have an electric charge and, accordingly, do not interact with other nuclei. The absence of a charge explains such a property of neutrons as a very high penetrating power.
Protons and neutrons are bound in the atomic nucleus by a very strong interaction. Now physicists agree that these two elementary nuclear particles are very similar to each other. So, they have equal backs, and nuclear forces they work exactly the same. The only difference is that the charge of the proton is positive, while the neutron has no charge at all. But since the electric charge in nuclear interactions does not matter, it can only be considered as a kind of label for the proton. If, however, to deprive the proton of an electric charge, then it will lose its individuality.
If you rub a glass rod on a sheet of paper, then the rod will acquire the ability to attract the leaves of the "sultan" (see Fig. 1.1), fluffs, thin streams of water. When combing dry hair with a plastic comb, the hair is attracted to the comb. In these simple examples we meet with the manifestation of the forces that are called electrical.
Rice. 1.1. Attracting the leaves of the "sultan" with an electrified glass rod.
Bodies or particles that act on surrounding objects by electrical forces are called charged or electrified. For example, the glass rod mentioned above, after being rubbed against a sheet of paper, becomes electrified.
Particles have an electrical charge if they interact with each other through electrical forces. Electric forces decrease as the distance between particles increases. The electrical forces are many times greater than the forces gravity.
Electric charge- This physical quantity, which determines the intensity of electromagnetic interactions. Electromagnetic interactions are interactions between charged particles or bodies.
Electric charges are divided into positive and negative. Stable elementary particles have a positive charge. protons And positrons, as well as ions of metal atoms, etc. The stable negative charge carriers are electron And antiproton.
There are electrically uncharged particles, that is, neutral: neutron, neutrino. These particles do not participate in electrical interactions, since their electric charge is zero. There are particles without electric charge, but there is no electric charge without a particle.
On glass rubbed with silk, positive charges arise. On ebonite, shabby on fur - negative charges. Particles repel each other with charges of the same sign ( charges of the same name), and for different signs ( unlike charges) particles are attracted.
All bodies are made up of atoms. Atoms are made up of a positively charged atomic nucleus and negatively charged electrons that move around the atomic nucleus. The atomic nucleus consists of positively charged protons and neutral particles - neutrons. The charges in an atom are distributed in such a way that the atom as a whole is neutral, that is, the sum of the positive and negative charges in the atom is zero.
Electrons and protons are part of any substance and are the smallest stable elementary particles. These particles can exist indefinitely in a free state. The electric charge of the electron and proton is called the elementary charge.
elementary charge is the minimum charge that all charged elementary particles have. The electric charge of the proton is equal in absolute value to the charge of the electron:
E \u003d 1.6021892 (46) * 10 -19 C The value of any charge is a multiple of the absolute value of the elementary charge, that is, the charge of the electron. Electron in translation from the Greek electron - amber, proton - from the Greek protos - the first, neutron from the Latin neutrum - neither one nor the other.
Conductors and dielectrics
Electric charges can move. Substances in which electric charges can move freely are called conductors. All metals are good conductors (conductors of the first kind), aqueous solutions salts and acids electrolytes(conductors of the second kind), as well as hot gases and other substances. The human body is also a conductor. Conductors are highly conductive, meaning they conduct electricity well.
Substances in which electric charges cannot move freely are called dielectrics(from English dielectric, from Greek dia - through, through and English electric - electric). These substances are also called insulators. The electrical conductivity of dielectrics is very low compared to metals. Porcelain, glass, amber, ebonite, rubber, silk, gases at room temperature, and other substances are good insulators.
The division into conductors and insulators is arbitrary, since conductivity depends on various factors, including temperature. For example, glass insulates well only in dry air and becomes a poor insulator in high humidity.
Conductors and dielectrics play a huge role in the modern application of electricity.