Emission and absorption. Bohr's quantum postulates
Types of optical spectra.
Absorption and emission of light
atoms. Origin of rulers
spectra
Comprehending the universe, know everything, not
selecting:
What is inside, you will find in the outside.
So accept it without looking back
The world has clear riddles.
Goethe
dependence of the indicator
refraction of matter and
the speed of light in it from
frequency of the light wave.
White light is a complex light, it consists of
simple rays, which, when passing through
the prism is deflected, but does not decompose, and only
in total, monochromatic rays give
feeling of white light. lens
gap
Spectral devices - devices,
well separating waves of different lengths and preventing overlap of individual parts of the spectrum.
prism Continuous spectrum
Red-hot
solids
Red-hot
liquids
Gases under high
pressure
The main role in radiation is played by
excitation of atoms and molecules during
chaotic
movement
these
particles,
caused by high temperature. Line spectrum
a spectrum consisting of individual sharply defined colored lines,
separated from each other by wide dark spaces.
A substance emits light only completely
certain wavelengths. Each of
lines have a finite width.
The spectra are obtained from luminous atomic gases or vapors.
sodium
The line spectra of various chemical elements differ in color,
position and number of individual luminous lines. Band spectrum
consists of separate stripes separated by dark spaces.
Each strip represents
totality large number Very
closely spaced lines.
Emitted by individual excited molecules (molecular gas).
The radiation is caused by both electronic
transitions in atoms, and oscillatory movements the atoms themselves in
molecule. Band spectrum
Continuous spectrum
Line spectrum
Emission spectrum
obtained by decomposing light emitted
self-luminous bodies. Absorption spectrum
obtained by passing light from a source giving a continuous spectrum through a substance,
whose atoms and molecules are in an unexcited state.
takeovers
Na
emissions
Na
H
H Law of spectral reversibility
lines:
absorption lines correspond
emission lines, i.e. atoms
less heated substance
absorb from the continuous spectrum
exactly the frequencies they are in
other conditions emit.
Gustav Robert Kirchhoff
12. 03. 1824 - 17. 10. 1887
10.
Spectrum of each atom chemical element unique.11.
Spectral analysis is a method for studying chemicalcomposition various substances according to them
spectra.
Spectral analysis
emission is called emission.
G. Kirchhoff
Analysis carried out using spectra
absorption is called absorption spectral analysis.
V. Bunsen
12.
Emission analysis:1. Each element has its own spectrum,
which does not depend on the methods of excitation.
2. The intensity of spectral lines depends on the concentration of the element in a given substance.
Performing analysis:
1. Make the atoms of this substance emit light with a line spectrum.
2. Decompose this light into a spectrum and determine the wavelengths of the observed
there are lines in it.
13.
Application of spectral analysismetallurgy
mechanical engineering
Nuclear industry
geology
archeology
criminology
14.
How to explain whythe atoms of each chemical element have
its own strictly individual set of spectral
lines?
Why do they match?
emission lines and
absorption in the spectrum
given elements?
What are the reasons for
differences in spectra
different atoms
elements?
15.
Postulate of stationary states:the atomic system may be
only in special stationary
(quantum) states, each of
which correspond to a certain
energy on which an atom is located
does not emit or absorb energy.
Frequency rule: when an atom transitions
from one stationary state to
other is emitted or absorbed
quantum of energy.
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27. /Tasks for tickets.doc
28. /Contents.doc Mechanical motion Relativity of motion, Reference system, Material point, Trajectory. Path and movement. Instant speed. Acceleration. Uniform and uniformly accelerated movement
Ticket No. 10 Crystalline and amorphous bodies. Elastic and plastic deformations of solids. Response plan
Law of thermodynamics. Application of the first law to isoprocesses. Adiabatic process
Coulomb's law. Law of conservation of electric charge
Capacitance of the capacitor. Application of capacitors
Work and power in a DC circuit. Electromotive force. Ohm's law for a complete circuit
Magnetic field, conditions of its existence. The effect of a magnetic field on an electric charge and experiments confirming this effect. Magnetic induction
Semiconductors. Intrinsic and impurity conductivity of semiconductors. Semiconductor devices
Law of electromagnetic induction. Lenz's rule
The phenomenon of self-induction. Inductance. Electromagnetic field
1. Definition. Oscillatory circuit Thompson's formula
Newton's Law Answer Plan
Electromagnetic waves and their properties. Principles of radio communication and examples of their practical use
Wave properties of light. Electromagnetic theory of light
Ticket No. 22 Rutherford's experiments on the scattering of α-particles. Nuclear model of the atom Answer plan Rutherford's experiments. Nuclear model of the atom. The word "atom" in Greek means "indivisible"
Ticket No. 23 Bohr's quantum postulates. Emission and absorption of light by atoms. Spectral analysis
Ticket number 24 Photo effect and its laws. Einstein's equation for the photoelectric effect and Planck's constant. Application of the photoelectric effect in the Plav answer technique
Ticket No. 25 Composition of the nucleus of an atom. Isotopes. Binding energy of the nucleus of an atom. Nuclear chain reaction, conditions for its implementation. Thermonuclear reactions
Ticket No. 26 Radioactivity. Types of radioactive radiation and methods of their registration. Biological effects of ionizing radiation Answer plan
Law of conservation of momentum in nature and technology
The law of universal gravitation. Gravity. Body weight. Zero Gravity Response Plan
Ticket 5 Transformation of energy during mechanical vibrations. Free and forced vibrations. Resonance Response Plan
Ticket No. 6 Experimental substantiation of the basic principles of the structure of matter. Mass and size of molecules. Avogadro's Constant Plan Answer
Ticket number 7 Ideal gas. Basic equation μt of an ideal gas. Temperature and its measurement. Absolute Temperature Answer Plan
Ticket No. 8 Equation of state of an ideal gas. (Mendeleev-Clapeyron equation.) Isopropes Answer plan
Ticket No. 9 Evaporation and condensation. Saturated and unsaturated pairs. Air humidity. Air Humidity Measurement Answer Plan
Problems applying the law of conservation of energy
Countdown. Material point. Trajectory. Path and movement. Instant speed. Acceleration. Uniform and uniformly accelerated motion
Ticket No. 23
Bohr's quantum postulates. Emission and absorption of light by atoms. Spectral analysis
Response Plan
1. First postulate. 2. Second postulate. 3. Types of spectra.Bohr based his theory on two postulates. The first postulate: an atomic system can only be in special stationary or quantum states, each of which has its own energy; In a stationary state, the atom does not radiate.
This means that an electron (for example, in a hydrogen atom) can be in several well-defined orbits. Each electron orbit corresponds to a very specific energy.
Second postulate: during the transition from one stationary state to another, a quantum is emitted or absorbed electromagnetic radiation. The energy of a photon is equal to the difference in the energies of an atom in two states: hv = E m – Εn; h= 6.62 10 -34 J s, where h- Planck's constant.
When an electron moves from a near orbit to a more distant one, the atomic system absorbs a quantum of energy. When an electron moves from a more distant orbit to a closer orbit relative to the nucleus, the atomic system emits an energy quantum.
Bohr's theory made it possible to explain the existence of line spectra.
Emission spectrum(or absorption) is a set of waves of certain frequencies that an atom of a given substance emits (or absorbs).
There are spectra solid, lined And striped.
Continuous spectra emit all substances in a solid or liquid state. The solid spectrum contains waves of all frequencies of visible light and therefore appears as a color band with a smooth transition from one color to another in the following order: Red, Orange, Yellow, Green, Blue and Violet (Every Hunter Wants to Know Where the Pheasant Sits).
Line spectra emit all substances in the atomic state. Atoms of all substances emit sets of waves of very specific frequencies that are unique to them. Just as each person has his own personal fingerprints, so the atom of a given substance has its own spectrum, characteristic only for it. Line emission spectra appear as colored lines separated by spaces. The nature of line spectra is explained by the fact that the atoms of a particular substance have only its own stationary states with their own characteristic energy, and therefore their own set of pairs of energy levels that the atom can change, i.e., an electron in an atom can only move from one specific orbits to other, well-defined orbits for a given chemical substance.
Striped spectra emitted by molecules. Striped spectra look similar to line spectra, only instead of individual lines, separate series of lines are observed, perceived as individual bands.
What is characteristic is that whatever spectrum is emitted by these atoms, the same is absorbed, i.e., the emission spectra according to the set of emitted frequencies coincide with the absorption spectra. Since atoms of different substances correspond only to them spectra, then there is a way to determine chemical composition substances by studying their spectra. This method is called spectral analysis. Spectral analysis is used to determine the chemical composition of fossil ores during mining, to determine the chemical composition of stars, atmospheres, planets; is the main method for monitoring the composition of a substance in metallurgy and mechanical engineering.
Please help me answer questions on physics. 1) Absorption and emission of light by an atom. 2 Ampere force, Lorentz force, multiple times given by the author Neurologist the best answer is 1)
Bohr's theory made it possible to explain the existence of line spectra.
The emission (or absorption) spectrum is a set of waves of certain frequencies that are emitted (or absorbed) by an atom of a given substance.
Spectra are solid, line and striped.
Continuous spectra emit all substances in a solid or liquid state. A continuous spectrum contains waves of all frequencies visible light and therefore looks like a stripe of color with a smooth transition from one color to another in the following order: red, orange, yellow, green, blue and purple (every hunter wants to know where the pheasant is sitting).
Line spectra emit all substances in the atomic state. Atoms of all substances emit sets of waves of very specific frequencies that are unique to them. Just as each person has his own personal fingerprints, so the atom of a given substance has its own spectrum, characteristic only for it. Line emission spectra appear as colored lines separated by spaces. The nature of line spectra is explained by the fact that the atoms of a particular substance have only its own stationary states with their own characteristic energy, and therefore their own set of pairs of energy levels that the atom can change, i.e., an electron in an atom can only move from one specific orbits to other, well-defined orbits for a given chemical substance.
Banded spectra are emitted by molecules. Striped spectra look similar to line spectra, only instead of individual lines, separate series of lines are observed, perceived as individual bands. What is characteristic is that whatever spectrum is emitted by these atoms, the same is absorbed, i.e., the emission spectra according to the set of emitted frequencies coincide with the absorption spectra. Since atoms of different substances correspond to spectra that are unique to them, there is a way to determine the chemical composition of a substance by studying its spectra. This method is called spectral analysis. Spectral analysis is used to determine the chemical composition of fossil ores during mining, to determine the chemical composition of stars, atmospheres, planets; is the main method for monitoring the composition of a substance in metallurgy and mechanical engineering.
2) Ampere power.
A current-carrying conductor in a magnetic field experiences a force equal to
F = I·L·B·sina
I is the current strength in the conductor;
L is the length of the conductor located in the magnetic field;
a - angle between vector magnetic field and the direction of current in the conductor.
The force acting on a current-carrying conductor in a magnetic field is called the Ampere force.
The maximum ampere force is:
F = I L B
It corresponds to a = 900.
Lorentz force.
The Lorentz force is determined by the relation:
Fl = q·V·B·sina
where q is the magnitude of the moving charge;
V is the module of its speed;
B - module of the magnetic field induction vector;
a is the angle between the charge velocity vector and the magnetic induction vector.
Reply from Kirill Starkov[newbie]
1. Bohr based his theory on two postulates. The first postulate: an atomic system can only be in special stationary or quantum states, each of which has its own energy; In a stationary state, the atom does not radiate.
This means that an electron (for example, in a hydrogen atom) can be in several well-defined orbits. Each electron orbit corresponds to a very specific energy.
The second postulate: during the transition from one stationary state to another, a quantum of electromagnetic radiation is emitted or absorbed. The energy of a photon is equal to the difference between the energies of an atom in two states: hv = Em – Εn; h = 6.62 10-34 J s, where h is Planck’s constant.
When an electron moves from a near orbit to a more distant one, the atomic system absorbs a quantum of energy. When an electron moves from a more distant orbit to a closer orbit relative to the nucleus, the atomic system emits an energy quantum.
Bohr's theory made it possible to explain the existence of line spectra.
2. Ampere force is the force with which a magnetic field acts on a current-carrying conductor placed in it.
The force exerted by a magnetic field on charges moving in it is called the Lorentz force.
Crib
An emission or absorption spectrum is a set of waves of certain frequencies that an atom of a given substance emits or absorbs. Continuous spectra emit all substances in a solid or liquid state. Line spectra emit all substances in the atomic state. Just as each person has his own personal fingerprints, the atom of a given substance has its own spectrum that is characteristic only of it.
Ticket No. 2 3
Bohr's quantum postulates. Emission and absorption of light by atoms. Spectral analysis
Response plan
1. First postulate. 2. Second postulate. 3. Types of spectra.
Bohr based his theory on two postulates. First postulate:an atomic system can only be in special stationary or quantum states, each of which has its own energy; In a stationary state, the atom does not radiate.
This means that an electron (for example, in a hydrogen atom) can be in several well-defined orbits. Each electron orbit corresponds to a very specific energy.
Second postulate:during the transition from one stationary state to another, a quantum of electromagnetic radiation is emitted or absorbed.The energy of a photon is equal to the difference in the energies of an atom in two states: hv = Е m Ε n; h = 6.62 10 -34 J s, where h Planck's constant.
When an electron moves from a near orbit to a more distant one, the atomic system absorbs a quantum of energy. When an electron moves from a more distant orbit to a closer orbit relative to the nucleus, the atomic system emits an energy quantum.
Bohr's theory made it possible to explain the existence of line spectra.
Emission spectrum(or takeovers) this is a set of waves of certain frequencies that an atom of a given substance emits (or absorbs).
There are spectra solid, lined and striped.
Continuous spectraemit all substances in a solid or liquid state. The solid spectrum contains waves of all frequencies of visible light and therefore appears as a color band with a smooth transition from one color to another in the following order: Red, Orange, Yellow, Green, Blue and Violet (Every Hunter Wants to Know Where the Pheasant Sits).
Line spectraemit all substances in the atomic state. Atoms of all substances emit sets of waves of very specific frequencies that are unique to them. Just as each person has his own personal fingerprints, so the atom of a given substance has its own spectrum, characteristic only for it. Line emission spectra appear as colored lines separated by spaces. The nature of line spectra is explained by the fact that the atoms of a particular substance have only its own stationary states with their own characteristic energy, and therefore their own set of pairs of energy levels that the atom can change, i.e., an electron in an atom can only move from one specific orbits to other, well-defined orbits for a given chemical substance.
Striped spectraemitted by molecules. Striped spectra look similar to line spectra, only instead of individual lines, separate series of lines are observed, perceived as individual bands.
What is characteristic is that whatever spectrum is emitted by these atoms, the same is absorbed, i.e., the emission spectra according to the set of emitted frequencies coincide with the absorption spectra. Since atoms of different substances correspond only to them spectra, then there is a way to determine the chemical composition of a substance by studying its spectra. This method is calledspectral analysis.Spectral analysis is used to determine the chemical composition of fossil ores during mining, to determine the chemical composition of stars, atmospheres, planets; is the main method for monitoring the composition of a substance in metallurgy and mechanical engineering.
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According to Bohr's postulates, an electron can be in several specific orbits. Each electron orbit corresponds to a certain energy. When an electron moves from a near to a distant orbit, an atomic system absorbs a quantum of energy. When an electron moves from a more distant orbit to a closer orbit relative to the nucleus, the atomic system emits an energy quantum.
Spectra
Bohr's theory made it possible to explain the existence of line spectra.
Formula (1) gives a qualitative idea of why atomic emission and absorption spectra are lined. In fact, an atom can emit waves only of those frequencies that correspond to differences in energy values E 1 , E 2 , . . . , E n ,. . That is why the emission spectrum of atoms consists of separately located sharp bright lines. At the same time, an atom can absorb not any photon, but only one with energy hν which is exactly equal to the difference E n − Ek some two allowed energy values E n And Ek. Moving to a higher energy state E n, atoms absorb exactly the same photons that they are capable of emitting during the reverse transition to the original state Ek. Simply put, atoms take from the continuous spectrum those lines that they themselves emit; This is why the dark lines of the absorption spectrum of a cold atomic gas are located exactly in those places where the bright lines of the emission spectrum of the same gas in a heated state are located.
Continuous spectrum hydrogen emission spectrum hydrogen absorption spectrum
The word "atom" translated from Greek means "indivisible." Under the Atom for a long time, until the beginning of the 20th century, meant the smallest indivisible particles of matter. By the beginning of the 20th century. Science has accumulated many facts that speak about complex structure atoms.
Great success in the study of the structure of atoms were achieved in the experiments of the English scientist Ernest Rutherford on the scattering of α-particles when passing through thin layers of matter. In these experiments, a narrow beam of α particles emitted radioactive substance, was directed onto thin gold foil. A screen was placed behind the foil, capable of glowing under the impacts of fast particles. It was found that most α-particles deviate from straight-line propagation after passing through the foil, that is, they are scattered, and some α-particles are generally thrown back. Rutherford explained the scattering of α-particles by the fact that the positive charge is not uniformly distributed in a ball with a radius of 10 -10 m, as previously assumed, but is concentrated in the central part of the atom - the atomic nucleus. When passing near the nucleus, an a-particle having a positive charge is repelled from it, and when it hits the nucleus, it is thrown into opposite direction. This is how particles that have the same charge behave, therefore, there is a central positively charged part of the atom, in which a significant mass of the atom is concentrated. Calculations showed that to explain the experiments, it is necessary to take the radius of the atomic nucleus to be approximately 10 -15 m.
Rutherford suggested that the atom was structured like a planetary system. The essence of Rutherford's model of the structure of the atom is as follows: in the center of the atom there is a positively charged nucleus in which all the mass is concentrated; electrons rotate around the nucleus in circular orbits at large distances (like planets around the Sun). The charge of the nucleus coincides with the number of the chemical element in the periodic table.
h is Planck's constant.
1. The word “atom” translated from Greek means “indivisible.” For a long time, until the beginning of the 20th century, an atom meant the smallest indivisible particles of matter. By the beginning of the 20th century. Science has accumulated many facts that indicate the complex structure of atoms.
Great advances in the study of the structure of atoms were achieved in the experiments of the English scientist Ernest Rutherford on the scattering of alpha particles when passing through thin layers of matter. In these experiments, a narrow beam of alpha particles emitted by a radioactive substance was directed at thin gold foil. A screen was placed behind the foil, capable of glowing under the impacts of fast particles. It was found that the majority of α-particles deviate from straight-line propagation after passing through the foil, i.e., they are scattered, and some α-particles are generally thrown back. Rutherford explained the scattering of alpha particles by the fact that the positive charge is not uniformly distributed in a ball with a radius of 10^~10 m, as previously assumed, but is concentrated in the central part of the atom - the atomic nucleus. When passing near the nucleus, an a-particle having a positive charge is repelled from it, and when it hits the nucleus, it is thrown back in the opposite direction. This is how particles that have the same charge behave, therefore, there is a central positively charged part of the atom, in which a significant mass of the atom is concentrated. Calculations showed that to explain the experiments, it is necessary to take the radius of the atomic nucleus to be approximately 10^~15 m.
Rutherford suggested that the atom was structured like a planetary system. The essence of Rutherford's model of the structure of the atom is as follows: in the center of the atom there is a positively charged nucleus in which all the mass is concentrated; electrons rotate around the nucleus in circular orbits at large distances (like planets around the Sun). The charge of the nucleus coincides with the number of the chemical element in the periodic table.
Rutherford's planetary model of atomic structure could not explain a number of known facts: an electron with a charge must fall onto the nucleus due to Coulomb forces of attraction, and an atom is a stable system; When moving in a circular orbit, approaching the nucleus, the electron in the atom must radiate electromagnetic waves all possible frequencies, i.e. the emitted light must have a continuous spectrum, but in practice it turns out differently: the electrons of atoms emit light that has a line spectrum. The Danish physicist Nielier Bohr was the first to try to resolve the contradictions in the planetary nuclear model of atomic structure.
Bohr based his theory on two postulates. The first postulate: an atomic system can only be in special stationary or quantum states, each of which has its own energy; in a stationary state, an atom does not emit. This means that an electron (for example, in a hydrogen atom) can be located in several well-defined orbits. Each electron orbit corresponds to a very specific energy.
The second postulate: during the transition from one stationary state to another, a quantum of electromagnetic radiation is emitted or absorbed. The energy of a photon is equal to the difference between the energies of an atom in two states: , where
h is Planck's constant.
When an electron moves from a nearby orbit to a more distant one, the atomic system absorbs a quantum of energy. When an electron moves from a more distant orbit to a closer orbit relative to the nucleus, the atomic system emits an energy quantum.
In science, for a very long time it was believed that an Atom is the smallest, INDIVISIBLE particle of matter.
| 1. The first to violate these ideas was Thomson: he believed that an atom is a kind of positive substance in which electrons are interspersed “like raisins in a cupcake.” The importance of this theory is that the atom was no longer recognized as indivisible |  |
| 2. Rutherford conducted an experiment on the scattering of alpha particles. Heavy elements (gold foil) were bombarded with radioactive material. Rutherford expected to see glowing circles, but he saw glowing rings. | |
| Rutherford's explanation: The center of the atom contains all the positive charge, and the electrons have no effect on the flow of alpha particles. | |
| 3. Planetary model of the hydrogen atom according to BORU | By emitting a portion of energy (visible), an atom gives only its own set of wavelengths - a spectrum. Types of spectra: 1. Radiation (emission) spectrum: (provided by bodies in a heated state) a) Solid - give all atoms in solid, liquid or dense gases b) Lined - give atoms in a gaseous state 1. Absorption spectrum: if light is passed through a substance, then this substance will absorb exactly those waves that it emits in a heated state (dark stripes appear on the continuous spectrum) Spectral analysis is a method for determining the chemical composition of a substance from its emission or absorption spectrum. The method is based on the fact that each chemical element has its own set of wavelengths. Application of spectral analysis: in criminology, medicine, astrophysics. A spectrograph is a device for performing spectral analysis. A spectroscope differs from a spectrograph in that it can be used not only to observe spectra, but also to take a photograph of the spectrum. Ticket No. 21 1. Thermodynamic approach to study physical phenomena. Internal energy and ways to change it. First law of thermodynamics. Application of the first law of thermodynamics to isothermal, isochoric and adiabatic processes. 2. Models of the structure of the atomic nucleus; nuclear forces; nucleon model of the nucleus; nuclear binding energy; nuclear reactions. 1. Each body has a very specific structure; it consists of particles that move chaotically and interact with each other, therefore any body has internal energy. Internal energy is a quantity characterizing the body’s own state, i.e. the energy of the chaotic (thermal) movement of microparticles of the system (molecules, atoms, electrons, nuclei, etc.) and the energy of interaction of these particles. Internal energy of a monatomic ideal gas determined by the formula U = 3/2 t/M RT. The internal energy of a body can change only as a result of its interaction with other bodies. There are two ways to change internal energy: heat transfer and commissioning mechanical work(for example, heating by friction or compression, cooling by expansion). Heat transfer is a change in internal energy without doing work: energy is transferred from more heated bodies to less heated ones. Heat transfer is of three types: thermal conductivity (direct exchange of energy between chaotically moving particles of interacting bodies or parts of the same body); convection (transfer of energy by flows of liquid or gas) and radiation (transfer of energy by electromagnetic waves). The measure of the transferred energy during heat transfer is the quantity of heat (Q). These methods are quantitatively combined into the law of conservation of energy, which for thermal processes reads as follows: the change in the internal energy of a closed system is equal to the sum of the amount of heat transferred to the system and the work of external forces performed on the system. , where is the change in internal energy, Q is the amount of heat transferred to the system, A is the work of external forces. If the system itself does the work, then it is conventionally designated A*. Then the law of conservation of energy for thermal processes, which is called the first law of thermodynamics, can be written as follows: , i.e. the amount of heat transferred to the system goes towards doing work by the system and changing its internal energy. During isobaric heating, the gas does work on external forces, where V1 and V2 are the initial and final volumes of the gas. If the process is not isobaric, the amount of work can be determined by the area of the ABCD figure enclosed between the line expressing the dependence p(V) and the initial and final volumes of gas V
Let us consider the application of the first law of thermodynamics to isoprocesses occurring with an ideal gas. In an isothermal process, the temperature is constant, therefore, the internal energy does not change. Then the equation of the first law of thermodynamics will take the form: , i.e., the amount of heat transferred to the system goes to perform work during isothermal expansion, which is why the temperature does not change. In an isobaric process, the gas expands and the amount of heat transferred to the gas goes to increase its internal energy and to perform work: . During an isochoric process, the gas does not change its volume, therefore, no work is done by it, i.e. A = 0, and the equation of the first law has the form , i.e., the transferred amount of heat goes to increase the internal energy of the gas. Adiabatic is a process that occurs without heat exchange with environment. Q = 0, therefore, when a gas expands, it does work by reducing its internal energy, therefore, the gas cools. The curve depicting the adiabatic process is called adiabatic. The nucleus of an atom of any substance consists of protons and neutrons. ( Common name protons and neutrons - nucleons.) The number of protons is equal to the charge of the nucleus and coincides with the number of the element in the periodic table. The sum of the number of protons and neutrons is equal to the mass number. For example, the nucleus of an oxygen atom consists of 8 protons and 16 - 8 = 8 neutrons. The nucleus of an atom consists of 92 protons and 235 - 92 = 143 neutrons. The forces that hold protons and neutrons in the nucleus are called nuclear forces. This is the most strong look interactions. In 1932, English physicist James Chadwick discovered particles with zero electrical charge and unit mass. These particles were called neutrons. The neutron is designated n. After the discovery of the neutron, physicists D. D. Ivanenko and W. Heisenberg in 1932 put forward the proton-neutron model of the atomic nucleus. According to this model, the nucleus of an atom of any substance consists of protons and neutrons. (The common name for protons and neutrons is nucleons.) The number of protons is equal to the charge of the nucleus and coincides with the element number in the periodic table. The sum of the number of protons and neutrons is equal to the mass number. For example, the nucleus of an oxygen atom consists of 8 protons and 16 - 8 = 8 neutrons. The nucleus of an atom consists of 92 protons and 235 - 92 = 143 neutrons. Chemical substances that occupy the same place in the periodic table, but have different atomic mass, are called isotopes. Isotopic nuclei differ in the number of neutrons. For example, hydrogen has three isotopes: protium - the nucleus consists of one proton, deuterium - the nucleus consists of one proton and one neutron, tritium - the nucleus consists of one proton and two neutrons. If we compare the masses of nuclei with the masses of nucleons, it turns out that the mass of the nucleus of heavy elements more than the amount the masses of protons and neutrons in the nucleus, and for light elements the mass of the nucleus is less than the sum of the masses of protons and neutrons in the nucleus. Therefore, there is a mass difference between the mass of the nucleus and the sum of the masses of protons and neutrons, called the mass defect. M = Mn - (Mp + Mn). A fission chain reaction is a nuclear reaction in which the particles causing the reaction are formed as products of the reaction. A necessary condition for the development of a fission chain reaction is the requirement k > 1, where k is the neutron multiplication factor, i.e., the ratio of the number of neutrons in a given generation to their number in the previous generation. Ability to chain nuclear reaction possesses the uranium isotope 235U. If certain critical parameters are present (critical mass - 50 kg, spherical shape with a radius of 9 cm), three neutrons released during the fission of the first nucleus fall into three neighboring nuclei, etc. The process is underway in the form of a chain reaction that occurs in a fraction of a second in the form nuclear explosion. Uncontrolled nuclear reaction is used in atomic bombs. The physicist Enrico Fermi was the first to solve the problem of controlling the chain reaction of nuclear fission. It was invented by him nuclear reactor in 1942. In our country, the reactor was launched in 1946 under the leadership of I.V. Kurchatov. Thermonuclear reactions are reactions of fusion of light nuclei that occur when high temperature(approximately 107 K and above). Prerequisites for the synthesis of helium nuclei from protons are available in the interior of stars. On Earth, thermonuclear reactions have only been carried out in experimental explosions, although international research is being conducted to control this reaction. If we compare the masses of nuclei with the masses of nucleons, it turns out that the mass of the nucleus of heavy elements is greater than the sum of the masses of protons and neutrons in the nucleus, and for light elements the mass of the nucleus is less than the sum of the masses of protons and neutrons in the nucleus. Therefore, there is a mass difference between the mass of the nucleus and the sum of the masses of protons and neutrons, called the mass defect. M = Mn - (Mp + Mn). Since there is a connection between mass and energy, then during the fission of heavy nuclei and during the synthesis of light nuclei, energy must be released that exists due to a mass defect, and this energy is called the binding energy of the atomic nucleus. The release of this energy can occur during nuclear reactions. A nuclear reaction is a process of changing the charge of a nucleus and its mass, which occurs when a nucleus interacts with other nuclei or elementary particles. When nuclear reactions occur, the laws of conservation of electrical charges and mass numbers are satisfied: the sum of the charges (mass numbers) of nuclei and particles entering into a nuclear reaction is equal to the sum of the charges (mass numbers) of the final products (nuclei and particles) of the reaction.
These are promising areas of nuclear energy. Since this energy can be used for peaceful purposes. An example of this is Nuclear power plants. Sea ships, icebreakers powered by nuclear power plants. Great progress in the study of the structure of atoms was achieved in the experiments of the English scientist Ernest Rutherford on the scattering of alpha particles when passing through thin layers of matter. In these experiments, a narrow beam of α-particles emitted by a radioactive substance was directed at thin gold foil. A screen was placed behind the foil, capable of glowing under the blows of fast α particles. It was found that the majority of α-particles deviate from rectilinear propagation after passing through the foil, i.e., they are scattered, and some α-particles are generally thrown back. Calculations showed that to explain the experiments it is necessary to accept Rutherford suggested that the atom was structured like a planetary system. The essence of Rutherford's model of the structure of the atom is as follows: in the center of the atom there is a positively charged nucleus in which all the mass is concentrated; electrons rotate around the nucleus in circular orbits at large distances (like planets around the Sun). The charge of the nucleus coincides with the number of the chemical element in the periodic table. Rutherford's planetary model of the structure of the atom could not explain a number of known facts: an electron with a charge must fall onto the nucleus due to Coulomb attractive forces, and an atom is a stable system. When moving in a circular orbit, approaching the nucleus, an electron in an atom must emit electromagnetic waves of all possible frequencies, i.e., the emitted light must have a continuous spectrum, but in practice it turns out differently: the electrons of atoms emit light that has a line spectrum. The Danish physicist Niels Bohr was the first to try to resolve the contradictions in the planetary nuclear model of atomic structure. Bohr based his theory on two postulates. The first postulate: an atomic system can only be in special stationary or quantum states, each of which has its own energy; In a stationary state, the atom does not radiate. This means that an electron (for example, in a hydrogen atom) can be in several well-defined orbits. Each electron orbit corresponds to a very specific energy. Second postulate: during the transition from one stationary state to another, a quantum of electromagnetic radiation is emitted or absorbed. The energy of a photon is equal to the difference between the energies of an atom in two states: , , where is Planck’s constant. When an electron moves from a nearby orbit to a more distant one, the atomic system absorbs a quantum of energy. When an electron moves from a more distant orbit to a closer orbit relative to the nucleus, the languid system emits an energy quantum. Bohr's theory made it possible to explain the existence of line spectra. Ticket number 24 1. What structure does the nucleus of an atom have? What features do nuclear forces have? Define the mass defect and binding energy of the atomic nucleus. Give examples of nuclear reactions. In 1932 after the discovery of the proton and neutron by scientists D.D. Ivanenko (USSR) and W. Heisenberg (Germany) put forward a proton-neutron model of the atomic nucleus According to this model: X – chemical element symbol Properties: 1. At distances of the order of 10 -13 cm, strong interactions correspond to attraction, and as the distance decreases, they correspond to repulsion. 2.Independent of availability electric charge(property of charge independence). The same force acts on both the proton and the neutron. 3. Interact with a limited number of nucleons (saturation property). 4.Short-range: quickly decrease, starting from r ≈ 2.2. 10 -15 m. The energy required to completely split a nucleus into individual nucleons is called binding energy. The binding energy is very high. When 4 g of helium is synthesized, the same amount of energy is released as when burning two cars of coal. The mass of the nucleus is always less than the sum of the rest masses of the free protons and neutrons that make it up. Formula for calculating binding energy:
m p – proton rest mass; m n is the rest mass of the neutron. M i is the mass of the atomic nucleus. In atomic physics, it is convenient to express mass in atomic mass units: 1 amu=1.67·10 -27 kg. Energy-mass coupling coefficient (equal to 2): s 2 = 931.5 MeV/a e m. Nuclear reactions - transformations of atomic nuclei caused by their interactions with various particles or with each other. Symbolic notation: A + a = B + b. When writing nuclear reactions, the laws of conservation of charge and mass number (number of nucleons) are used. Examples:
The energy yield of a nuclear reaction is the difference between the total binding energy of the particles participating in the reaction and the reaction products. Reactions that occur with the release of energy are called. exothermic, with absorption - endothermic. Ernest Rutherford is one of the founders of the fundamental doctrine of internal structure atom. The scientist was born in England, in a family of immigrants from Scotland. Rutherford was the fourth child in his family, and turned out to be the most talented. Special Contribution he managed to introduce the theory of atomic structure.
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A fission chain reaction is a nuclear reaction in which the particles causing the reaction are formed as products of the reaction. The uranium isotope 235 U has the ability to undergo a nuclear chain reaction. If certain critical parameters are present (critical mass - 50 kg, spherical shape with a radius of 9 cm), three neutrons released during the fission of the first nucleus fall into three neighboring nuclei, etc. The process continues in the form of a chain reaction that occurs in a split second in the form of a nuclear explosion. Uncontrolled nuclear reactions are used in atomic bombs. The physicist Enrico Fermi was the first to solve the problem of controlling a chain reaction of nuclear fission. He invented a nuclear reactor in 1942. In our country, the reactor was launched in 1946 under the leadership of I.V. Kurchatov.
Thermonuclear reactions are reactions of the fusion of light nuclei that occur at high temperatures (about 107 K and above). The necessary conditions for the synthesis of helium nuclei from protons exist in the interior of stars. On Earth, thermonuclear reactions have only been carried out in experimental explosions, although international research is being conducted to control this reaction.
- mass defect.
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