What is quantum physics with simple words. Quantum physics for dummies: essence with simple words

Quantum-mechanical concepts

Nature descriptions

In a sense, all modern physics There are quantum physics! She, in essence, is the result of the "newest revolution in natural science."

What does quantum physics study?

First of all, quantum physics is a theory that describes the properties of matter at the micro-reference level. It explores the laws of the movement of quantum objects, which are also called micro-lectures.

The concept of a micro belt is one of the main in quantum physics. These include molecules, atoms, atomic nuclei, elementary particles. Their characteristic feature is very small sizes - 10 ^ -8 cm and less. The most important characteristics of microjects include a mass of peace and an electric charge. Electron Mass ME \u003d 9.1 · 10 ^ -28 g, Proton has a mass of 1836me, neutron - 1839me, Muon - 207me. Photon and neutrinos do not have peace masses - it is zero. The magnitude of the electrical charge of any microject is multiple the charge value of the electron equal to 1.6 · 10 ^ -19 CL. Along with charged, neutral microjects exist, the charge of which is zero. The electrical charge of the complex microject is equal to the algebraic sum of the charges of the components of its particles. One of the most important specific characteristics of micro-trades is the spin (from the English word "rotate"). Although the spin is interpreted as the torque of the microject pulse, which is not associated with its movement as a whole, non-existentable and independent of external conditions, but it is impossible to represent it as a rotating top. It has a purely quantum nature - there is no analogues in classical physics. The presence of a spin makes significant features in the behavior of the micromyr objects.

Most microjects are unstable - they spontaneously, without any effects on the part, disintegrate, turning into others, including elementary, particles. Unstable is a specific, but not mandatory property of microjects. Along with unstable, there are also stable microjects: photon, electron, proton, neutrinos, stable atomic nuclei, atoms and molecules are mainly state.

Quantum physics is still theoretical Foundation Modern teaching on the structure and properties of the substance and fields.

It is important to understand that quantum physics does not cancel the classical, and contains it as its limit case. When moving from microjects to conventional macroscopic objects, its laws become classic, and thus quantum physics set the limits of the applicability of classical physics. The transition from classical physics to quantum is the transition to a deeper level of consideration of matter.

Quantum physics has become an essential step in building a modern physical picture of the world. She allowed to predict and explain a huge number of different phenomena - from the processes occurring in atoms and atomic nuclei, to macroscopic effects in solids; Without it, it is impossible, as it appears now, to understand the origin of the universe. The range of quantum physics is wide - from elementary particles to space objects. Without quantum physics, not only natural science is unthinkable, but also modern technique.

WikiHow works on the principle of wiki, which means that many of our articles are written by several authors. When creating this article on its editing and improvement, they worked, including anonymous, 11 people (a).

Quantum physics (it is a quantum theory or quantum mechanic) - this is a separate direction of physics, which is engaged in the description of the behavior and the interaction of matter and energy at the level of elementary particles, photons and some materials at very low temperatures. The quantum field is defined as "action" (or in some cases angular momentum) particles, which in size is within the limits of a tiny physical constant, which is called a constant plank.

Steps

permanent Planck

Start with the study of the physical concept of a constant plank. In quantum mechanics, a constant plank is a quantum of action, referred to as h.. Similarly, for interacting elementary particles, quantum moment of impulse - This is the reduced strap line (permanent strap divided by 2 π) is indicated as ħ And called "H with a feature." The value of a constant plank is extremely small, it combines the moments of the impulse and the designation of actions that have a more general mathematical concept. Name quantum mechanics It implies that some physical quantities like the moment of impulse can only change discrete, not continuous ( cm. Analog) way.

• For example, the moment of an electron pulse attached to the atom or molecule is quantized and can only take the values \u200b\u200bof a multiple of the above constant plank. This quantization increases the electron orbital on a series of a whole primary quantum number. In contrast, the moment of impulse of unrelated electrons, located near, is not quantized. The constant plate is also used in the quantum theory of light, where the light quantum is photon, and the matter interacts with the energy by the transition of electrons between the atoms or the "quantum jump" of the associated electron.
• The units of constant plank can also be considered as time of energy. For example, in the subject area of \u200b\u200belementary particle physics, virtual particles are represented as the mass of particles that spontaneously arise from vacuum in a very small area and play a role in their interaction. The limit of the life of these virtual particles is the energy (mass) of each particle. Quantum mechanics has a large subject area, but in each mathematical part there is a constant plank.

1. Learn about heavy particles. Heavy particles pass from the classic to the quantum energy transition. Even if a free electron, which has some quantum properties (such as rotation), as an unbound electron, approaches the atom and slows down (possibly due to the emitting of the photons), it moves from classic to quantum behavior, since its energy is lowered below Ionization energy. The electron binds to the atom and its moment of the pulse with respect to the atomic kernel is limited by the quantum value of the orbit, which it can occupy. This transition is sudden. It can be compared with a mechanical system that changes its condition from unstable to stable, or its behavior varies with a simple chaotic, or can even be compared with a rocket ship, which slows down and goes below the separation rate, and occupies orbit around some star or Another celestial object. Unlike them, photons (which are weightless) such a transition is not carried out: they simply crosses the space unchanged until they interact with other particles and do not disappear. If you look at the night sky, photons from some stars without change fly long years years, then interact with the electron in the molecule of your retina, emitting your energy, and then disappearing.

I think we can say that no one understands the quantum mechanics

Physicist Richard Feynman

The statement that the invention of semiconductor devices was a revolution, will not be exaggerated. It is not only an impressive technological achievement, but it also paved the way for events that forever change modern society. Semiconductor devices are used in all sorts of microelectronics devices, including computers, individual types of medical diagnostic and medical equipment, popular telecommunication devices.

But behind this technological revolution is even more, revolution in general science: region quantum theory. Without this, the jump in the understanding of the natural world, the development of semiconductor devices (and more advanced developed electronic devices) would never be possible. Quantum physics is an incredibly complex section of science. This chapter is given only short review. When scholars of the Fainman level say that "no one understands [this]," you can be sure that it is really a difficult topic. Without a basic understanding of quantum physics or at least understanding scientific discoverieswhich led to their development, it is impossible to understand how and why semiconductor electronic devices work. Most electronics textbooks are trying to explain semiconductors from the point of view of "classical physics", as a result, making them even more confusing to understand.

Many of us have seen the diagrams of atom models that are similar to the drawing below.

Atom of Rutherford: Negative electrons rotate around a small positive kernel

Tiny particles of matter called protons and neutrons, constitute the center of the atom; electrons Rotate as the planet around the star. The kernel carries a positive electrical charge, due to the presence of protons (neutrons have no electrical charge), while the atom balancing negative charge is in the electron-moving orbit. Negative electrons are attracted to positive protons, as the planets are attracted by the force of attraction to the Sun, however, the orbits are stable due to the movement of electrons. We are obliged to this popular model of an atom of the work of Ernest Rauntford, which in about 1911 experimentally determined that the positive charges of atoms are concentrated in a tiny, dense kernel, and not evenly distributed in diameter, as previously assumed the explorer J. J. Thomson.

The refordation on scattering experiment is the bombardment of the fine gold foil positively charged alpha particles, as shown in the figure below. Young graduate students of H. Geiger and E. Marsden received unexpected results. The trajectory of the movement of some alpha particles was rejected to a large angle. Some alpha particles were scattered in the opposite direction, at an angle of almost 180 °. Most of the particles passed through the Golden Foil without changing the path the path, as if foil was not at all. The fact that several alpha particles have experienced great deviations in the trajectory of movement, indicates the presence of nuclei with a small positive charge.

Rangeford scattering: a bunch of alpha particles dissipates fine gold foil

Although the Rangeford atom model was confirmed by experimental data better than Thomson's model, it was still imperfect. There were further attempts to determine the structure of the atom, and these efforts helped pave the way for strange discoveries of quantum physics. Today our understanding of the atom is a bit more difficult. Nevertheless, despite the revolution of quantum physics and its contribution to our understanding of the structure of the atom, the image of the solar system of Rutherford as an atom structure, passed into the mass consciousness to the so far that it remains in the fields of education, even if it is inappropriate.

Consider it short description electrons in the atom taken from the popular electronics textbook:

Rotating negative electrons are attracted to a positive kernel, which leads us to the question of why electrons do not fly into the nucleus atom. The answer is that rotating electrons remain at their stable orbit due to two equal, but opposite forces. The centrifugal force acting on the electrons is directed to the outside, and the strength of the charge of charges is trying to attract electrons to the kernel.

In accordance with the Rutherford model, the author considers electrons with solid pieces of matter engaged in round orbits, their attraction inside to the oppositely charged kernel is balanced by their movement. The use of the term "centrifugal force" is technically incorrect (even for planets rotating in orbits), but it is easy to forgive because of the popular adoption of the model: in fact, there is no such thing as power, repulsiveanyone Rotating body from the center of its orbit. It seems that this is because the inertia of the body strive to preserve its movement in a straight line, and since the orbit is a constant deviation (acceleration) from the straight movement, there is a constant inertia opposition to any power that attracts the body to the center of the orbit (centripetal), be That gravity, electrostatic attraction, or even the tension of the mechanical connection.

Nevertheless, the real problem with this explanation, first of all, is the idea of \u200b\u200belectrons moving in circular orbits. The proven fact that accelerated electrical charges emit electromagnetic radiation, this fact was known even during refordford times. As rotary traffic It is an acceleration form (a rotating object in constant acceleration, leading an object from a normal straight line), electrons in the rotating state must dispose of radiation like dirt from the bouquet wheel. Electrons accelerated in circular trajectories in particle accelerators called synchrotrons, as you know, do it, and the result is called synchrotron radiation. If the electrons lose energy in such a way, their orbits would ultimately be disturbed, and as a result they would face a positively charged core. However, inside the atoms it usually does not occur. Indeed, electronic "orbits" are surprisingly resistant in a wide range of conditions.

In addition, experiments with "excited" atoms showed that the electromagnetic energy is emitted by an atom only at certain frequencies. Atoms are "excited" by external influences, such as the light, as is known to absorb energy and return the electromagnetic waves at certain frequencies, as a tankboard that does not ring at a certain frequency until it is hit. When the light emitted by an excited atom is divided into component frequencies (colors), individual lines of colors in the spectrum are detected, the pattern of spectral lines is unique to the chemical element. This phenomenon is usually used to identify chemical elements, and even to measure the proportions of each element in a compound or chemical mixture. According to solar system Atomic Rangeford model (with respect to electrons, like pieces of matter freely rotating in orbit with some radius) and the laws of classical physics, excited atoms must return the energy in a practically infinite frequency range, and not on selected frequencies. In other words, if the refordeford model was correct, there would be no "Kametonon" effect, and the color spectrum emitted by any atom would look like a continuous band of colors, and not as a few separate lines.

The Borov model of the hydrogen atom (with orbits drawn in scale implies the finding of electrons only in discrete orbits. Electrons moving with n \u003d 3,4,5 or 6 to n \u003d 2 are displayed on a series of spectral lines of Balmer

The researcher named Nils Bohr attempted to improve the Rutherford model, after studying it in the Rutherford laboratory for several months in 1912. Trying to agree on the results of other physicists (in particular, Max Planck and Albert Einstein), Bor suggested that each electron had a certain, specific amount of energy, and that their orbits are distributed in such a way that each of them can occupy certain places around the kernel like balls fixed on circular paths around the kernel, and not as freely moving satellites, as previously assumed (drawing above). In respect of the laws of electromagnetism and accelerating charges, Bor referred to the "orbits" as stationary statesTo avoid interpretation that they were moving.

Although the ambitious attempt at the rethinking of the structure of an atom, which was closer to the experimental data, and was an important milestone in physics, but was not completed. Its mathematical analysis was better predicted by the results of experiments compared with the analyzes produced according to previous models, but also remained without answering questions about why Electrons should behave in such a strange way. The assertion that electrons existed in stationary quantum states around the kernel, correlated with experimental data better than the Rostford model, but did not say that the electrons make these special states. The answer to this question was to come from another physics Louis de Brogly after about ten years.

Debriel suggested that electrons like photons (particles of light) have both particle properties and wave properties. Relying on this assumption, he suggested that the analysis of rotating electrons from the point of view of waves is better suited than from the point of view of particles, and can give more understanding about their quantum nature. And indeed, in understanding, another breakthrough was performed.

The string is vibrating on the resonant frequency between two fixed dots forms a standing wave

Atom, according to de Brogle, consisted of standing waves, a phenomenon, well known to physicists in various forms. As the turf string of a musical instrument (drawing above), vibrating on a resonant frequency, with "nodes" and "anti-nose" in stable places along its length. Debriel presented electrons around atoms in the form of waves curved in a circle (figure below).

"Rotating" electrons like standing wave around the kernel, (a) two cycles in orbit, (b) three cycles in orbit

Electrons can only exist on certain, specific "orbits" around the nucleus, because they are the only distances on which the ends of the waves coincide. With any other radius, the wave will be destroyed with itself and, thus, will cease to exist.

De Broglya hypothesis gave both mathematical support and a convenient physical analogy to explain the quantum states of electrons inside the atom, but its atom model was still incomplete. For several years of Physics, Werner Geisenberg and Erwin Schrödinger, working independently from each other, worked on the concept of corpuscular-wave dualism de Broglie to create more stringent mathematical models of subatomic particles.

This theoretical promotion from the primitive model of the standing wave de Broglie to the models of the Geisenberg matrix and differential equation Schrödinger was given the name Quantum mechanics, it introduced a rather shocking characteristic into the world of subatomic particles: a sign of likelihood, or uncertainty. According to a new quantum theory, it was impossible to determine the exact position and the exact pulse of the particle at one moment. A popular explanation of this "principle of uncertainty" was that there was a measurement error (that is, trying to accurately measure the position of the electron, you interfere with the impulse, and, therefore, you can't know what was before measuring the position, and vice versa). The sensational output of quantum mechanics is that the particles do not have accurate positions and pulses, and due to the connection of these two magnitudes, their cumulative uncertainty will never decrease below a certain minimum value.

This form of communication "uncertainty" exists in other areas, except for quantum mechanics. As discussed in the chapter of the "Mixed Frequency AC Signals" of Tom 2 of this series of books, there are mutually exclusive links between confidence in the time domain of the signal form and its data in frequency domain. Simply put, the more we know its component frequencies, the less accurately we know his amplitude in time, and vice versa. Quote myself:

The infinite duration signal (infinite number of cycles) can be analyzed with absolute accuracy, but the smaller the cycles are available to a computer for analysis, the less the accuracy of the analysis ... the less signal periods, the less accuracy of its frequency. Taking this concept to its logical extreme, a short pulse (not even a complete signal period) does not really have a certain frequency, is an infinite frequency range. This principle is common to all wave phenomena, and not just for voltages and currents.

To accurately determine the amplitude of the changing signal, we must measure it in a very short period of time. However, the execution of this limits our knowledge of the frequency of the wave (the wave in quantum mechanics should not be similar to a sinusoidal wave; such a similarity is a special case). On the other hand, to determine the frequency of the wave with great accuracy, we must measure it within large number Periods, which means we will lose sight of its amplitude at any given moment. Thus, we cannot simultaneously know the instant amplitude and all frequencies of any wave with unlimited accuracy. Another oddity, this uncertainty is much more inaccuracy of the observer; It is in the very nature of the wave. This is not the case, although it would be, given the relevant technologies, to provide accurate measurements and instant amplitude, and frequencies at the same time. IN literal senseThe wave can not accurate instantaneous amplitude and accurate frequency at the same time.

The minimum uncertainty of the position of the particle and impulse, expressed by Heisenberg and Schrödinger, has nothing to do with the measurement limit; Rather, this is the internal property of the nature of the corpuscular-wave dualism of the particle. Consequently, the electrons do not really exist in their "orbits" as accurately certain particles of matter or even as defined waves forms, but rather as "clouds" - technical term wave function The probability distribution, as if each electron was "scattered" or "smeared" in the range of positions and impulses.

This radical view of the electrons, as at uncertain clouds, initially contradicts the initial principle of quantum electron states: electrons exist in discrete defined "orbits" around the atomic core. This new look, in the end, was a discovery that led to the formation and explanation of quantum theory. As strange it seems that the theory created to explain the discrete behavior of electrons ends, declaring that electrons exist as "clouds", and not as separate pieces of matter. However, the quantum behavior of electrons does not depend on electrons having certain values \u200b\u200bof coordinates and impulse, but from other properties called quantum numbers. In essence, quantum mechanics do without the common concepts of the absolute position and absolute moment, and replaces them with absolute concepts of such types that have no analogues in general practice.

Even if the electrons are known to exist in the infertility, "cloud" forms of a distributed probability, and not in the form of individual parts of matter, these "clouds" have several other characteristics. Any electron in the atom can be described by four numeric measures (mentioned earlier by quantum numbers), which are called the main thing (radial), orbital (azimuthal), magnetic and spin numbers. The following is a brief overview of each of these numbers:

The main (radial) quantum number: denoted by the letter n.This number describes the shell on which an electron resides. The electronic "shell" represents the area of \u200b\u200bspace around the atom core, on which electrons can exist, corresponding to the models of a stable "standing wave" de Broglie and Bohr. Electrons can "jump" from the shell on the shell, but cannot exist between them.

The main quantum number should be a positive integer (large or equal to 1). In other words, the main quantum number of the electron cannot be 1/2 or -3. These integers were chosen not arbitrarily, but through experimental evidence of the light spectrum: different frequencies (colors) of light emitted by excited hydrogen atoms follow a mathematical dependence depending on the specific integer values, as shown in the figure below.

Each shell has the ability to hold several electrons. The concentric rows of seats in the amphitheater can be brought as an analogy for electronic shells. Just as a person sitting in the amphitheater must choose a row to sit down (it cannot sit between the rows), the electrons must "choose" a specific shell to "sit down". Like rows in the amphitheater, the extreme shells hold more electrons compared to shells closer to the center. Also, the electrons seek to find the smallest affordable shell, as people in the amphitheater are looking for a place nearest to the central scene. The higher the shell number, the greater the energy of the electrons on it.

The maximum number of electrons that any shell can retain, the 2N 2 equation is described, where N is the main quantum number. Thus, the first shell (n \u003d 1) may contain 2 electrons; The second shell (n \u003d 2) is 8 electrons; and the third shell (n \u003d 3) - 18 electrons (drawing below).

The main quantum number N and maximum amount electrons are associated with formula 2 (N 2). Orbits are not scale.

Electronic shells in the atom were denoted by letters, not numbers. The first shell (n \u003d 1) was indicated k, the second shell (n \u003d 2) l, the third shell (n \u003d 3) m, the fourth shell (n \u003d 4) n, the fifth shell (n \u003d 5) o, the sixth sheath ( n \u003d 6) p, and seventh shell (n \u003d 7) B.

Orbital (azimuthal) quantum number: Shell, consisting of submaroes. Someone can be more convenient to think about subordrodes as simple sections of the shells, like stripes dividing the road. The submarine is much more strange. The submarkets are areas of space where electronic "clouds" can exist, and in fact various sublicas have various forms. The first submarine in the shape of a ball (figure below (S)), which makes sense when visualized as an electron cloud surrounding the atom core in three dimensions.

The second submarine resembles a dumbbell consisting of two "petals", connected at one point near the center of the atom (figure below (P)).

The third submarine is usually reminiscent of a set of four "petals" grouped around the nucleus of the atom. These shapes of the submarkets resemble graphic images of an antennic pattern of antennas with petals similar to the bulbs extending from the antenna in different directions (Figure below (D)).

Orbital:
(s) three-time symmetry;
(p) shown: P x, one of three possible orientations (P x, p y, p z), along the relevant axes;
(d) Showing: D x 2 -Y 2 is similar to D xy, d yz, d xz. Shown: D z 2. Number of possible D-orbitals: Five.

The permissible values \u200b\u200bof the orbital quantum number are positive integers, as well as for the main quantum number, but also include zero. These quantum numbers for electrons are denoted by the letter L. The number of suburbs is equal to the main quantum number of the shell. Thus, the first shell (n \u003d 1) has one subband with number 0; The second shell (n \u003d 2) has two submaroes with numbers 0 and 1; The third shell (n \u003d 3) has three submaroes with numbers 0, 1 and 2.

The old agreement description of the submarines used the letters, not the numbers. And this format, the first submarine (L \u003d 0) was designated S, the second submarine (L \u003d 1) was designated P, the third submarine (L \u003d 2) was designated D, and the fourth submarine (L \u003d 3) was designated f. Letters came from words: sharp., principal, diffuse and fundamental. You still can see these designations in many periodic tables used to designate the electronic configuration of external ( valentines) Atom shells.

(a) the representation of the silver atom on Boru,
(b) AG orbital representation with the separation of shells on the submarine (orbital quantum number L).
This diagram does not imply anything about the actual position of electrons, but represents only energy levels.

Magnetic quantum number: The magnetic quantum number for an electron classifies, the orientation of the electron submarine shape. The "petals" sublicas can be directed in several directions. These different orientations are called orbital. For the first submarine (S; L \u003d 0), which resembles the sphere, the "direction" is not specified. For the second (p; l \u003d 1), the submarine in each shell, which resembles a dumbbell indicating in three possible directions. Present three dumbbells intersecting at the beginning of the coordinates, each is directed along its axis in the three-axle coordinate system.

The permissible values \u200b\u200bfor this quantum number consist of integers, ranging from -l to L, and denotes the number as m L. in atomic physics and l Z. In nuclear physics. To calculate the number of orbitals in any subhead, you need to double the number of the submarine and add 1 (2 ∙ L + 1). For example, the first submarine (L \u003d 0) in any shell contains one orbital with the number 0; The second submarine (L \u003d 1) in any shell contains three orbitals with numbers -1, 0 and 1; The third submarine (L \u003d 2) contains five orbital with numbers -2, -1, 0, 1 and 2; etc.

Like the main quantum number, the magnetic quantum number arose directly from the experimental data: the effect of zeeman, the separation of spectral lines, exposing ionized gas magnetic fieldFrom here and the name "Magnetic" quantum number.

Spin quantum number: Like a magnetic quantum number, this property of an atom electrons was detected using experiments. Careful observation of spectral lines showed that each line was in fact a pair of very closely arranged lines, it was the assumption that this so-called thin structure It was the result of each electron, "rotating" around its axis, as a planet. Electrons with different "rotation" would give a slightly different light frequency when exciting. The concept of a rotating electron is currently outdated, being more suitable for (wrong) to look at the electrons, as on separate particles of matter, and not as on the "clouds", but the name remains.

Spin quantum numbers are indicated as m S. in atomic physics and s Z. In nuclear physics. On each orbital on each subhead in each shell, there may be two electrons, one with back +1/2, and the other with spin -1/2.

Physicist Wolfgang Pauli developed the principle explaining the ordering of electrons in the atom in accordance with these quantum numbers. His principle called powli ban principle, It claims that two electrons in one atom cannot occupy the same quantum states. That is, each electron in the atom has a unique set of quantum numbers. This limits the number of electrons that can occupy any orbital, submarine and shell.

Here is shown the location of electrons in the hydrogen atom:

With one proton in the kernel, the atom takes one electron for its electrostatic balance (the proton's positive charge is equalized by the negative charge of the electron). This electron is located on the lower shell (n \u003d 1), the first submarine (L \u003d 0), on the only orbital (spatial orientation) of this submarine (M l \u003d 0), with the value of the spin 1/2. The general method of describing this structure is performed by transferring electrons in accordance with their shells and subordacities according to the agreement called spectroscopic designation. In this designation, the shell number is shown as an integer, the submarine as the letter (S, P, D, F), and the total number of electrons in the submarine (all orbitals, all the backs) as the upper index. Thus, hydrogen with its single electron, placed at the base level, is described as 1S 1.

Turning to the next atom (in order of the atomic number), we get helium element:

Atom helium consists of two protons in the kernel, and this requires two electrons to balance the double positive electric charge. Since two electrons are one with spin 1/2 and the other with spin -1/2 - are on the same orbital, the electronic structure of helium does not require additional submarches or shells to hold the second electron.

However, an atom requiring three or more electron will need additional subordrodes to hold all electrons, since only two electrons can be on the bottom shell (n \u003d 1). Consider the following atom in the sequence of increasing atomic numbers, lithium:

Lithium atom uses a part of the shell L Capacity (n \u003d 2). This shell actually has a total capacity of eight electrons (maximum shell capacity \u003d 2n 2 electrons). If we consider the structure of the atom with a fully filled L by the shell, we will see how all the combinations of submaroes, orbitals and spins are occupied by electrons:

Often, when prescribing an atom of spectroscopic designation, any fully filled shells are skipped, and not filled with shells and filled shells higher Level designated. For example, an neon element (shown in the figure above), which has two fully filled shells, can be spectrally described simply as 2p 6, and not as 1S 22 S 22 P 6. Lithium with its fully filled K-shell and the only electron on the L-shell can be described simply as 2s 1, and not 1S 22 S 1.

Skip fully filled down level shells is performed not only for convenience. It also illustrates the basic principle of chemistry: the chemical behavior of the element is primarily determined by its unfilled shells. And hydrogen, and lithium possesses on their outer shells with one electrone (AS 1 and 2S 1, respectively), that is, both elements have similar properties. Both have a high reactivity, and reacts in almost the same methods (binding to similar elements in similar conditions). It does not matter that lithium has a fully filled K-shell under an almost free L-shell: the unfilled L-shell is the sheath, which determines its chemical behavior.

Elements that have fully filled external shells are classified as noble and differ in almost complete absence of reactions with other elements. These elements were classified as inert when it was believed that they do not at all in the reaction, but, as is well known, they form connections with other elements under certain conditions.

Since items with the same electrons configurations in their external shells have similar chemical propertiesDmitry Mendeleev correspondingly organized chemical elements in the table. This table is known as And modern tables follow this common type shown in the figure below.

Periodic Table of Chemical Elements

Dmitry Mendeleev, Russian Chemist, was the first to have developed a periodic table of elements. Despite the fact that Mendeleev organized its table in accordance with the atomic mass, not atomic number, and created a table that was not so useful as modern periodic tables, its development acts as an excellent example of scientific evidence. Seeing the patterns of periodicity (similar chemical properties in accordance with the atomic mass), Mendeleev pushed the hypothesis that all elements should fit into this ordered scheme. When he discovered "empty" places in the table, he followed the logic of the existing order and suggested the existence of other unknown elements. The subsequent discovery of the ETE elements confirmed the scientific correctness of the hypothesis of Mendeleev, further discoveries led to the appearance of the periodic table that we use now.

Like this should Science work: hypotheses lead to logical conclusions and are accepted, changed or rejected depending on the consistency of experimental data with their conclusions. Any fool can formulate post-finish hypothesis to explain the existing experimental data, and many do it. What the scientific hypothesis differs from post-finish speculation is the prediction of future experimental data, which are not yet collected, and possibly refutation as a result of these data. Boldly, lead the hypothesis to its logical conclusion (s) and attempt to predict the results of future experiments, this is not a dogmatic leap of faith, but rather a public check of this hypothesis, an open challenge to opponents of the hypothesis. In other words, scientific hypotheses are always "risky" due to the attempt to predict the results of not yet carried out experiments, and therefore can be refuted if the experiments will pass as expected. Thus, if the hypothesis properly predicts the results of repeated experiments, its falsity is refuted.

Quantum mechanics, first as hypotheses, and then as the theory, turned out to be extremely successful in predicting the results of experiments, therefore, received a high degree of scientific confidence. Many scientists have reason to believe that this is an incomplete theory, since its forecasts are more truthful on a microphysical scale, and not in macroscopic sizes, but, nevertheless, it is an extremely useful theory for explaining and predicting the interaction of particles and atoms.

As you have already seen in this chapter, quantum physics is important when describing and predicting a variety of different phenomena. In the next section, we will see its meaning in electrical conductivity solids, including semiconductors. Simply put, nothing in chemistry or physics solid It does not make sense in the popular theoretical structure of electrons that exist as separate particles of matter spinning around the nucleus atom as miniature satellites. When electrons are treated as "wave functions" existing in certain, discrete states that are regular and periodic, then the behavior of the substance can be explained.

Let's summarize

Electrons in atoms exist in the "clouds" of a distributed probability, and not as discrete particles of matter rotating around the kernel, as miniature satellites, as the common examples show.

Separate electrons around the nucleus atom strive for unique "states" described by four quantum numbers: the main (radial) quantum number, known as shell; orbital (azimuthal) quantum number, known as oil; magnetic quantum numberdescribing orbital (orientation of the submarine); and spin quantum number, or simply spin. These states are quantum, that is, "between them" there are no conditions for the existence of an electron, in addition to states that fit into the quantum numbering scheme.

Bloom (Radial) Quantum Number (N) Describes a basic level of Or the shell on which an electron is located. The larger this number, the greater the radius of the electronic cloud from the nucleus of the atom, and the greater the electron energy. The main quantum numbers are integers (positive integers)

Orbital (azimuthal) quantum number (L) Describes the form of an electronic cloud in a specific shell or level and is often known as the "submarine". In any shell, so many subcases (forms of the electronic cloud), what is the main quantum number of the shell. Azimuthal quantum numbers are whole positive numbers starting with zero and ending with a number less than the main quantum number per unit (N - 1).

Magnetic Quantum Number (M L) Describes which orientation is a submarine (electronic cloud figure). The submarine can allow so many different orientations, which is equal to the double number of the submarine (L) plus 1, (2L + 1) (that is, for L \u003d 1, M l \u003d -1, 0, 1), and each unique orientation is called an orbital. These numbers are integers starting from the negative value of the submarine number (L) through 0 and ending with the positive value of the submarine number.

Spin quantum number (m s) Describes another electron property and can take +1/2 and -1/2 values.

Powli ban principle It says that two electrons in the atom cannot separate the same set of quantum numbers. Therefore, there may be no more than two electrons on each orbital (spin \u003d 1/2 and spin \u003d -1 / 2), 2L + 1 orbitals in each submarine, and n submaroes in each shell, and no more.

Spectroscopic designation - This is an agreement to denote the electronic structure of the atom. The shells are shown as integers, followed by the letters of submaroes (S, P, D, F) with numbers in the upper index, denoting the total number of electrons in each appropriate submarine.

The chemical behavior of the atom is determined exclusively by electrons in the unfilled shells. Low level shells that are completely filled with little or do not affect the chemical characteristics of the binding of elements.

Elements with fully filled electron shells are almost completely inert, and called noble Elements (previously known as inert).

29.10.2016

Despite the sonority and mysteriousness of today's theme, we will try to tell what is studying quantum physics, simple words which sections of quantum physics have a place to be and why need quantum physics in principle.

The material below is available for understanding anyone.

Before raking about what quantum physics is learning, it will be appropriate to remember, why it all began ...

By the middle of the XIX century, humanity came closely to study the problems, which, by attracting the apparatus of classical physics, it was impossible.

A number of phenomena seemed strange. Separate questions did not find an answer at all.

In the 1850s, William Hamilton, believing that classical mechanics are not able to accurately describe the movement of light rays, offers its own theory, which entered the history of science called the formalism of Hamilton-Jacobi, which was based on the postulate of the wave theory of light.

In 1885, arguing with a friend, Swiss and physicist Johann Balmer brought empirically formula that allowed the wavelengths of spectral lines with very high accuracy.

To explain the causes of the identified laws of Balmer then could not.

In 1895, Wilhelm X-rays, in the study of cathode rays, opened the radiation called by the X-rays (subsequently renamed to the rays), characterized by a powerful penetrating character.

Aven a year later - in 1896 - Henri Becquer, studying the salt of uranium, opened spontaneous radiation with similar properties. The new phenomenon was called radioactivity.

In 1899, the wave nature of X-rays was proved.

Photo 1. Rodonarchors of quantum physics Max Planck, Erwin Schrödinger, Niels Bor

The 1901 year year was marked by the appearance of the first planetary model of the atom proposed by Jean Perenom. Alas, the scientist himself refused this theory, not finding it confirmation from the standpoint of the theory of electrodynamics.

Two years later, a scientist from Japan Hantaro Nagaoka proposed the next planetary model of the atom, in the center of which there was a positively charged particle, around which electrons would rotate in orbits.

This theory, however, did not take into account the emission emitted by electrons, and therefore could not, for example, explain the theory of spectral lines.

Reflecting on the structure of the atom, in 1904, Joseph Thomson first interpreted the concept of valence from a physical point of view.

The year of birth of quantum physics, perhaps, you can recognize the 1900s, connecting the performance of Max Planck at a meeting of German physical.

It was the plaque that suggested that the theory, united by a set of scattered physical concepts, formulas and theories, including the Boltzmann's permanent, linking energy and temperature, the number of Avogadro, the Law of Wine Displacement, Electron Charge, Radiation Law -Boltsmann ...

It was also introduced into the use of the concept of a quantum of action (the second - after a constant Boltzmann - the fundamental constant).

Further development of quantum physics is directly connected with the names of Hendrik Lorenz, Albert Einstein, Ernst Rutherford, Arnold Zommerfeld, Max Born, Nielsa Bora, Erwin Schrödinger, Louis de Broglie, Werner Geisenberg, Wolfgang Pauli, Dirac field, Enrico Fermi and many other wonderful scientists, Worked in the first half of the 20th century.

Scientists succeeded in unprecedented depth to know the nature of elementary particles, study the interactions of particles and fields, to identify the quark nature of matter, to derive the wave function, to explain the fundamental concepts of discreteness (quantization) and corpuscular-wave dualism.

Quantum theory as no other brought humanity to understand the fundamental laws of the universe, replaced the usual concepts more accurate, forced to rethink a huge number of physical models.

What does quantum physics study?

Quantum physics describes the properties of matter at the micro-refinery level, exploring the laws of movement of microjects (quantum objects).

Subject of study of quantum physics Comerate quantum objects with dimensions of 10 -8 cm and less. It:

• molecules
• atoms
• atomic nuclei,
• elementary particles.

The main characteristics of microjects are resting and electric charge. Mass of one electron (ME) is 9.1 · 10 -28.

For comparison - the mass of the muon is 207 me, neutron - 1839 me, proton 1836 me.

Some particles do not have peace masses at all (neutrino, photon). Their mass is 0 me.

Electric charge of any microwkeect Koint charge value of an electron equal to 1.6 · 10 -19 CL. Along with charged, neutral microjects exist, the charge of which is zero.

Photo 2. Quantum physics forced to revise traditional views on the concepts of waves, fields and particles

The electrical charge of the complex microject is equal to the algebraic sum of the charges of the components of its particles.

Microstect properties include spin (In the literal translation from English - "rotate").

It is customary to interpret how the moment of the moment of the quantum object does not depend on the external conditions.

The back is difficult to choose an adequate image in the real world. It can not be represented by a rotating wolf due to his quantum nature. Classical physics describe this object is not capable.

The presence of the back influences the behavior of microjects.

The presence of a back makes significant features in the behavior of the micromyr objects, most of which are unstable objects - spontaneously disintegrates, turning into other quantum objects.

Stable microjects, which include neutrinos, electrons, photons, protons, as well as atoms and molecules, are able to disintegrate only under the influence of powerful energy.

Quantum physics completely absorbs classical physics, considering it with its limit case.

Actually quantum physics is - in a broad sense - modern physics.

What is described by quantum physics in a micrometer cannot be perceived. Because of this, many of the provisions of quantum physics are difficult to represent, in contrast to the objects described by classical physics.

Despite these, new theories made it possible to change our ideas about the waves and particles, a dynamic and probabilistic description, on continuous and discrete.

Quantum physics is not just a new-fashioned theory.

This theory that managed to predict and explain the incredible number of phenomena - from the processes flowing in atomic nuclei to macroscopic effects in outer space.

Quantum physics - in contrast to the classical physics - studies the matter on the fundamental level, giving interpretations of the ambient reality, which traditional physics is not able to (for example, why atoms retain stability or whether elementary particles are really elementary).

Quantum theory gives us the opportunity to describe the world more accurately than it was made before it occurs.

The value of quantum physics

Theoretical developments that constitute the essence of quantum physics are applicable to studying both unimaginably huge space objects and extremely small size of elementary particles.

Quantum electrodynamics Immerss us to the world of photons and electrons, making the emphasis on the study of interactions between them.

Quantum theory of condensed media Delites our knowledge of superfluid liquids, magnets, liquid crystals, amorphous bodies, crystals and polymers.

Photo 3. Quantum physics gave humanity a much more accurate description of the surrounding world

Scientific studies of the last decades are focused on the study of the quark structure of elementary particles within the framework of the independent branch of quantum physics - quantum chromodynamics.

Unrelativistic quantum mechanics (The one is beyond the framework of the theory of Einstein's relativity) is studying microscopic objects moving with a conditionally low speed (less than), the properties of molecules and atoms, their structure.

Quantum opticsit is engaged in scientific traversing facts associated with the manifestation of quantum properties of light (photochemical processes, thermal and forced radiation, photophobes).

Quantum field theory It is a unifying section that entered the ideas of the theory of relativity and quantum mechanics.

Scientific theories developed in the framework of quantum physics gave a powerful impetus to development, quantum electronics, technology, quantum theory of solid body, materials science, quantum chemistry.

Without the emergence and development of marked branches of knowledge, it would be impossible to create, spacecraft, atomic icebreaking, mobile communications and many other useful inventions.

Welcome to the blog! I am very glad to you!

Surely you heard many times on the inexplicable secrets of quantum physics and quantum mechanics. Her laws fascinate mystics, and even physicists themselves admit that they do not understand them completely. On the one hand, it is curious to understand these laws, but on the other hand, there is no time to read multi-volume and sophisticated books in physics. I really understand you, because I also love the knowledge and search for the truth, but the time for all books is catastrophically lacking. You are not alone, very many inquisitive people are gaining in the search bar: "Quantum physics for teapots, quantum mechanics for teapots, quantum physics for beginners, quantum mechanics for beginners, basics of quantum physics, basics of quantum mechanics, quantum physics for children, what is quantum Mechanics". It is for you this publication.

You will be understood by the basic concepts and paradoxes of quantum physics. From the article you will learn:

• What is interference?
• What is spin and superposition?
• What is "measurement" or "collapse of the wave function"?
• What is quantum confusion (or quantum teleportation for dummies)? (see Article)
• What is a mental experiment "Schrödinger Cat"? (see Article)

What is quantum physics and quantum mechanics?

Quantum mechanics are part of quantum physics.

Why is it so difficult to understand these sciences? The answer is simple: Quantum physics and quantum mechanics (part of quantum physics) are studying the laws of the micromyr. And these laws are absolutely different from the laws of our macromir. Therefore, it is difficult for us to imagine what is happening with electrons and photons in the micrometer.

An example of the difference between the laws of macro- and micromirov: In our macromir, if you put a ball into one of 2 boxes, then in one of them it will be empty, and in the other - the ball. But in the micrometer (if instead of a ball - an atom), an atom can be simultaneously in two boxes. This is repeatedly confirmed experimentally. Is it really difficult to accommodate it in your head? But you can't argue with the facts.

One more example. You photographed a rapidly rushing red sports car and saw a blurred horizontal strip in the photo, as if the car at the moment of the photo was from several points of space. Despite the fact that you see in the photo, you are still confident that the car is at one second when you are photographed was in one particular place in space. In the microy world, everything is wrong. An electron that rotates around the nucleus of the atom does not really rotate, but is at the same time in all points of the sphere around the nucleus of the atom. Like a wounded loose tangler fluffy wool. This concept in physics is called "Electronic cloud" .

A small excursion in history. For the first time about the quantum world, scientists thought when in 1900 the German physicist Max Planck tried to find out why, when heated, the metals change color. It was he who introduced the concept of a quantum. Before that, scientists thought that the light applies continuously. The first one who seriously perceived the opening of the plank was to anyone then unknown Albert Encen. He realized that the light was not only a wave. Sometimes he behaves like a particle. Enstein received the Nobel Prize for his discovery that the light is radiated by portions, quanta. A quantum of light is called a photon ( photon, Wikipedia) .

In order to make it easier to understand the laws of quantum physics and mechanics (Wikipedia), It is necessary in a sense to abstract from the usual laws of classical physics. And to imagine that you have come across, like Alice, in the rabbit Nora, in the country of miracles.

And here is a cartoon for children and adults. Talks about the fundamental experiment of quantum mechanics with 2 slots and observer. It lasts only 5 minutes. Look at him before we deepen in the main questions and concepts of quantum physics.

Quantum physics for teapots video. In the cartoon, pay attention to the "eye" of the observer. He became a serious mystery for physician scientists.

What is interference?

At the beginning of the cartoon, it was shown on the example of fluid, as waves behave - alternating dark and light vertical stripes appear on the screen with the slots. And in the case when the plate "shoot" discrete particles (for example, pebbles), they fly through 2 slots and fall on the screen directly opposite the gaps. And "draw" on the screen only 2 vertical stripes.

Interference light - This is a "wave" behavior of light when a lot of alternating bright and dark vertical stripes are displayed on the screen. Still these vertical stripes the interference pattern is called.

In our macromir, we often observe that the light behaves like a wave. If you put a hand in front of the candle, then the wall will be not a clear shadow of the hand, but with broken contours.

So, everything is not difficult! It is now quite clear to us that the light has a wave nature and if there are 2 slots to illuminate with light, then we will see the interference picture on the screen. Now consider the 2nd experiment. This is the famous Stern-Gerlacha experiment (which spent in the 20s of the last century).

The installation described in the cartoon is not light, but "fired" with electrons (as separate particles). Then, at the beginning of the last century, physics of the whole world believed that electrons are elementary particles of matter and should not have a wave nature, but the same as pebbles. After all, electrons are elementary particles of matter, right? That is, if they "throw" in 2 cracks, like pebbles, then on the screen for slots we must see 2 vertical stripes.

But ... the result was stunning. Scientists saw the interference picture - a lot of vertical stripes. That is, electrons, as well as light, can also have a wave nature, can interfer. And on the other hand, it became clear that the light is not only a wave, but a bit and a particle - a photon (from the historical reference at the beginning of the article we learned that the opening of Enstein received the Nobel Prize).

May remember, we were told at the school on physics about "Vaccular and wave dualism"? It means that when it comes to very small particles (atoms, electrons) of the microworld, then they are both waves and particles

Today, today we are so smart and we understand that 2 above the experiment described - the shooting of electrons and the lighting of the slot light is the essence of the same thing. Because we shoot the slots of quantum particles. Now we know that light, and electrons have a quantum nature, both waves and particles at the same time. And at the beginning of the 20th century, the results of this experiment were sensation.

Attention! Now let's get to a more subtle issue.

We shine on our cracks with a flow of photons (electrons) - and see the slots on the screen interference pattern (vertical stripes). It is clear. But we are interested to see how each electron flies in the slot.

Presumably, one electron flies into the left slot, the other is right. But then 2 vertical strips should appear on the screen directly opposite the slots. Why is the interference picture? Maybe electrons somehow interact with each other on the screen after span through the slots. And as a result, such a wave picture is obtained. How do we trace?

We will throw the electrons not a beam, but one by one. Throw, wait, throw the following. Now that an electron flies one, he will no longer interact on the screen with other electrons. We will register each electron on the screen after throwing. One or two of course not "draw" a clear picture. But when they send them a lot in the slots, we note ... oh horror - they again "painted" the interference wave picture!

We begin to slowly go crazy. After all, we expected 2 vertical stripes opposite the gaps! It turns out that when we threw photons one by one, each of them passed, as if after 2 cracks simultaneously and interferred with himself. Fiction! Let's return to the explanation of this phenomenon in the next section.

What is spin and superposition?

We now know what interference is. This is the wave behavior of micro particles - photons, electrons, other micro particles (let's call them photons from this moment to simplicity).

As a result of the experiment, when we threw in 2 slots of 1 photon, we realized that it flies as if two cracks simultaneously. Otherwise, how to explain the interference picture on the screen?

But how to present a picture that the photon flies through two cracks at the same time? There are 2 options.

• 1st option: Photon, like a wave (like water) "swims" through 2 slots at the same time
• 2nd option: Photon, like a particle, flies simultaneously on the 2nd trajectories (not even two, but at all at once)

In principle, these statements are equivalent. We came to the "integral on trajectories." This is the formulation of quantum mechanics from Richard Feynman.

By the way, it is Richard Feynman belongs to a known expression that confidently can argue that the quantum mechanics does not understand no one

But this expression worked at the beginning of the century. But now we are smart and know that the photon can behave and as a particle, and as a wave. That he can somehow incomprehensible for us to fly simultaneously after 2 slots. Therefore, we will easily understand the following important assertion of quantum mechanics:

Strictly speaking, the quantum mechanic tells us what is the behavior of the photon - a rule, and not an exception. Any quantum particle is usually in several states or at several points of space at the same time.

Macromir objects can only be in one specific place in one specific state. But the quantum particle exists in its laws. And she and things are not before that we do not understand them. On this - point.

We should simply recognize as axiom that the "superposition" of the quantum object means that it can be on 2 or more trajectories at the same time, in 2 or more points at the same time

The same applies to another parameter of the photon - back (its own angular momentum). Spin is a vector. The quantum object can be represented as a microscopic magnet. We are accustomed that the magnet vector (spin) is either directed up, or down. But the electron or photon again tell us: "Guys, we care about what you are accustomed, we can be in both states of the back immediately (vector up, vector down), just as we can be on 2 trajectories at the same time or In 2-points at the same time! "

What is "measurement" or "collapse of the wave function"?

We left a little - to understand more what is "measurement" and what is a "collapse of the wave function".

Wave function - This is a description of the status of a quantum object (our photon or electron).

Suppose we have an electron, he flies to himself in an indefinable state, the spin is directed and up, and down at the same time. We need to measure his condition.

We measure using a magnetic field: electrons in which the spin was directed towards the field direction, deviated in one direction, and electrons whose spin is directed against the field to another. More photons can be sent to a polarization filter. If the spin (polarization) of the photon +1 - it passes through the filter, and if -1, then no.

Stop! Here you will inevitably have a question: Before the measurement, because the electron did not have any particular direction of the back, right? He was in all states at the same time?

This is the chip and sensation of quantum mechanics. Until you measure the status of a quantum object, it can rotate in any direction (to have any direction of the vector of own angular momentum - spin). But at the moment when you measured his condition, it seems to make a decision, what a spin vector to take.

Here is such a cool, this quantum object - it decides on its state. And we cannot predict in advance what decision he will take when it flies into the magnetic field in which we measure it. The likelihood that he will decide to have a vector "up" or "down" - 50 by 50%. But as soon as he decided - it is in a certain state with a specific direction of the back. The reason for its solution is our "measurement"!

This is called " collapse of the wave function ". The wave function before the measurement was uncertain, i.e. The electron spin vector was simultaneously in all directions, after measuring the electron recorded a certain direction of the vector of its back.

Attention! Excellent for understanding Example-Association from our macromir:

Spread the coin on the table as Yulia. While the coin is spinning, the neo does not have a specific value - an eagle or a rush. But as soon as you decide to "measure" this value and put the coin with the hand, it is here that the concrete state of the coin is eagle or a rush. Now imagine that this coin makes a decision, what value to you "show" is an eagle or a rush. Also also behaves and electron.

And now remember the experiment shown at the end of the cartoon. When the photons were passed through the gaps, they behaved like a wave and showed an interference picture on the screen. And when scientists wanted to fix (measure) the moment of photons span through the gap and set the "observer" screen, the photons began to behave, not like waves, but as particles. And "drew" on the screen 2 vertical stripes. Those. At the time of measurement or observation, quantum objects themselves choose, in what state them.

Fiction! Is not it?

But that's not all. Finally we i got to the most interesting.

But ... it seems to me that the information will be overloaded, so 2 of these concepts we will look at separate posts:

• What ?
• What is a mental experiment.

And now, do you want the information to decompose on the shelves? Check the documentary prepared by the Canadian Institute of Theoretical Physics. In it in 20 minutes it is very brief and in chronological order you will tell you about all the discoveries of quantum physics, starting from the opening of the plan in 1900. And then tell what practical development is carried out now on the basis of knowledge on quantum physics: from the most accurate atomic hours to super-speed calculations of the quantum computer. I highly recommend watching this movie.

See you!

I wish you all inspiration for all planned plans and projects!

P.S.2 Write your questions and thoughts in the comments. Write, what other questions about quantum physics are you interested in?

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