The concept of "atom" came to us from distant antiquity, but completely changed the original meaning that the ancient Greeks put into it (translated from Greek, "atom" means "indivisible"). The etymology of the name "indivisible" reflects the essence of the atom exactly the opposite. An atom is divisible and consists of elementary particles.
The complexity of the structure of the atom is proved by fundamental discoveries made in the late 19th and early 20th centuries. as a result of studying the nature of cathode rays (J. Thomson, 1897), the discovery of the phenomenon of the photoelectric effect (A. G. Stoletov, 1889), the discovery of the radioactivity of chemical elements (A. Becquerel, M. Sklodowska-Curie, 1896-1899 .), determining the nature of α-particles (experiments by E. Rutherford, 1889-1900). Scientists came to the conclusion that atoms have their own structure, have a complex structure.
How did the classical theory of atomic structure develop?
In 1904, in his work "On the Structure of the Atom", J. Thomson described his model, which received the figurative name of "plum pudding".
In 1911, E. Rutherford proposed a planetary model of the atom.
In 1913, N. Bohr introduced quantum representations into E. Rutherford's planetary model of the atom.
In 1932, the proton-neutron theory of the nucleus was developed, according to which the nuclei of atoms consist of protons and neutrons.
Electrons, protons and neutrons are called elementary particles.
What are the properties of these particles?
Corpuscular-wave properties of the microworld. Elementary particles, as well as atomic nuclei, atoms and molecules built from them, have negligibly small masses and sizes and therefore have their own special properties, unlike those that objects of the macrocosm around us have. They form their own specific world - a microcosm described by the laws of quantum mechanics, which are largely applicable to particles with very small masses and very high velocities.
Quantum mechanics characterizes the particles of the microworld as objects with a dual nature - corpuscular-wave dualism: they are both particles (corpuscles) and waves.
The corpuscular-wave dualism of objects of the microworld is also confirmed by the interference and diffraction of electrons, protons, neutrons, atoms, etc., which are experimentally familiar to you from the course of physics.
An electron is a particle that determines the most characteristic chemical properties of atoms and molecules. The dual nature of the electron can be confirmed experimentally. If the electrons emitted by the source - the cathode - are passed through small holes in the plate placed in their path, then they, falling on the photographic plate, cause it to blacken. After developing the photographic plate, one can see on it a set of alternating light and dark rings, i.e., a diffraction pattern (Fig. 1).
Rice. one.
Electron diffraction patterns of gases (left) and crystals (right). The central spot is due to an unscattered electron beam, and the rings are due to electrons scattered at different angles
The diffraction pattern includes both diffraction - the rounding of an obstacle by a wave, and interference, i.e., the superposition of waves on top of each other. These phenomena prove that the electron has wave properties, since only waves are able to go around obstacles and overlap each other at their meeting points. However, getting on the photolayer, the electron gives blackening only in one place, which indicates the presence of corpuscular properties in it. If it were only a wave, it would more or less evenly illuminate the entire plate.
Due to diffraction, the electron, having passed the hole, can, in principle, fall into any point of the photographic plate, but with different probabilities, i.e., we can talk about the probability of detecting an electron in one or another region of the photolayer, and in the general case - in one or another region of space. Therefore, the motion of an electron in an atom cannot be considered as the motion of a point charge along a strictly defined closed trajectory.
Questions and tasks to § 1
- Name those phenomena that directly or indirectly prove that the atom is a complex particle.
- How did the classical theory of atomic structure develop? What models of atoms do you know? What is their essence? What are the disadvantages?
- Give examples of phenomena proving the dual (dualistic) nature of particles of the microworld.
- What is the difference between micro and macro objects?
- Elementary (smallest) particles are indivisible particles. How does such an assumption correspond to the statement of physicists that the elementary atomic particle - the electron - is divisible? By the way, it was the discovery of the divisibility of the electron that was awarded the Nobel Prize in 1998.
Sulfur chemical element- (Soufre French, Sulfur or Brimstone English, Schwefel German, θετον Greek, Latin Sulfur, whence the symbol S; atomic weight 32.06 at O=16 [Determined by Stas from the composition of silver sulfide Ag 2 S]) belongs among the most important non-metallic elements.
Sulfur, chemical element- (Soufre French, Sulfur or Brimstone English, Schwefel German, θετον Greek, Latin Sulfur, whence the symbol S; atomic weight 32.06 at O=16 [Determined by Stas from the composition of silver sulfide Ag2S]) belongs to the number the most important non-metallic elements. She is… … Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Compression in chemical reactions- In a large number of cases, chemical reactions are accompanied by a change in the volume of substances involved in the transformation. In the case when the volume of substances entering the reaction is greater than the volume of substances occurring during the reaction, a positive C is observed. ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Complex compounds- Cis platinum is one of many coordination compounds Complex compounds (Latin complexus combination, girth) or coordination compounds (l ... Wikipedia
Substance as matter- (Matière, Substance, Materie, Stoff, Matter) is opposed in meaning to spirit, force, form, appearance and emptiness. Such a negative definition, originating from antiquity, cannot serve as a basis for any scientific information about V. Science is ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Fermentation (chemical process)- represents a special chemical process caused by the so-called. enzymes. During the process of fermentation, a complex particle of organic matter decomposes into simpler ones, i.e., containing a smaller number of atoms. Among the huge number of fermentations, as ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Fermentation- (chemical process) is a special chemical process caused by the so-called. enzymes. During the process of fermentation, a complex particle of organic matter decomposes into simpler ones, i.e., containing a smaller number of atoms. Among the vast number ... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Efron
Fermentation- represents a special chemical process caused by so-called enzymes. During the fermentation process, a complex particle of organic matter breaks down into simpler ones, i.e. containing a smaller number of atoms. Among the huge number of fermentations, like ... ... Encyclopedia of Brockhaus and Efron
complex particle- sudėtingoji dalelė statusas T sritis fizika atitikmenys: engl. complex particle vok. zusammengesetztes Teilchen, n rus. complex particle, f pranc. particule constituante, f … Fizikos terminų žodynas
particle constituante- sudėtingoji dalelė statusas T sritis fizika atitikmenys: engl. complex particle vok. zusammengesetztes Teilchen, n rus. complex particle, f pranc. particule constituante, f … Fizikos terminų žodynas
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Targets and goals
Introduce students to the evolution of scientific views on the structure of the atom Show the interaction of the sciences of physics and chemistry
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An atom is an “indivisible” particle of a chemical element Evidence of the complexity of the structure of the atom Discovery of cathode rays (1897, J. Thomson) Discovery of X-rays (1895, K. Roentgen), phenomena of the photoelectric effect 1889, A.G. Stoletov) 3. The discovery of radioactivity (1896, A. Becquerel) and its study (1897-1903, spouses M. Sklodovskaya-Curie and P. Curie)
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THE WORD "ATOM" COMED OVER 2500 YEARS AGO ANCIENT GREEK PHILOSOPHER DEMOCRITES
ATOM IS THE SMALLEST CHEMICALLY INDIVIDUAL PARTICLE OF SUBSTANCE
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Ideas about the structure of the atom
Classical theory of the structure of the atom Models of the structure of the atom: 1. "Pudding with raisins" (1902-1904, J. Thomson and W. Kelvin 2. Planetary model (1907, E. Rutherford) 3. Bohr model (1913) Modern ideas about the structure of the atom based on quantum mechanics
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MODEL ATOMATOMSON
The atom, according to J. Thomson, is very similar to raisin pudding: electrons are like "raisins", and "porridge" is the positively charged substance of the atom. Joseph John Thomson
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STRUCTURE OF THE ATOM
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Postulates of N. Bohr
electrons in an atom rotate in strictly defined closed orbits, without emitting or absorbing energy; when electrons move from one orbit to another, energy is absorbed or released.
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Modern quantum model
N. Bohr is the creator of the first quantum theory of the atom and an active participant in the development of the foundations of quantum mechanics. He also made a significant contribution to the development of the theory of the atomic nucleus and nuclear reactions, the processes of interaction of elementary particles with the environment. The electron has a dual (particle-wave nature) -28-19 Mass \u003d 9.1 * 10 g; charge \u003d 1.6 * 10 C A moving electron has the properties of a wave (the ability to diffract interference)
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Modern model of the atom
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STRUCTURE OF THE ATOM
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STRUCTURE OF THE ATOM protons neutrons electrons atom nucleus electron shell
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Z is the serial number of the chemical element A is the mass number, A=Ar N is the number of neutrons
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Number pZ p = Z(serial number of the chemical element) Number ēZ ē = Z(serial number of the chemical element) Number n N = A – Z(mass number minus the serial number of the chemical element) + + o
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isotopes
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Nuclides -
different kinds of atoms. Nuclides are characterized by mass number A and nuclear charge Z. Isotopes - nuclides with the same Z, but different A Isobars - nuclides with different Z, but the same A
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Checking knowledge
Task 1. Write down for 2-3 elements (of your choice). Element Ordinal number Relative atomic mass Charge of the atomic nucleus Number of protons Number of neutrons Number of electrons
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Task 2. Perform the following exercises Name the element containing 23 protons. Name the elements of period II containing 8 neutrons and write them down. Name and write down the symbols of elements in which the sum of protons and neutrons is 40. The nucleus of an atom of a chemical element A contains 11 protons and 12 neutrons, and the nucleus of an atom of a chemical element B contains 12 protons and 12 neutrons. Determine if they are: a) isotopes of the same element; b) atoms of two chemical elements that have the same mass number; c) atoms of two different elements located side by side in the periodic system.
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Task 3. Determine the composition of isotopes 35Cl and 37Cl 28Si , 29Si, 30Si 39Ar, 40Ar
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View all slides
Atom -
complex particle
"Everything around
us consists of
indivisible particles
or atoms"
Democritus
(about 460 BC -
around 360 BC e.)
X-rays
Crystal
Diffractive
picture
Wilhelm Conrad Roentgen
German physicist
In 1895
University of Würzburg
Electrons
In 1897
John Thomson
English physicist
Cambridge university
Antoine Henri Becquerel
French physicist
1896
The phenomenon of radioactivity
blackening
Manifested
photographic plate
Uranium salts
Maria Sklodowska-Curie
Pierre Curie
Polish physical chemist
French physical chemist
In 1903
Discovery of radium
Opening
polonium
"Pudding Model"
John Thomson
English physicist
In 1904
Electrons make oscillatory movements, due to which the atom emits electromagnetic energy, and the atom itself is electrically neutral.
Ernest Rutherford
English physicist
Scattering of an α-particle
In 1907
"Planetary Model"
Quantum theory
Niels Bohr
Danish physicist
Electrons move in closed orbits in accordance with the value of their energy, which is not released or absorbed at the same time.
In 1913
An electron can move from one allowed energy state to another, emitting or absorbing energy in the process.
Dmitry Dmitrievich
Werner Karl
Ivanenko
Heisenberg
Russian physicist
German theoretical physicist
In 1932
Nucleons = Protons (Z)+ Neutrons (N)
Proton - neutron
theory
A is the mass number of the atom
are types of chemical atoms
isotopes
elements that have the same
atomic number, but different mass numbers.
Number of electrons
Core charge
Number of protons (Z)
Serial number
Electron
Mass
Protons
Electrons
A change in the number of protons in an atom leads to the formation of a new chemical element, because the charge of the atom's nucleus changes.
1 proton (Z)
1 proton (Z)
A change in the number of neutrons in an atom leads to a change in the atomic mass of the element.
Isotopes of hydrogen differ in their properties.
Deuterium
An element is a collection of atoms with the same nuclear charge.
Oxygen
free atoms
Simple substances
oxygen
ozone
Complex Substances
CH₃ - O - CH₃
С₂Н ₅ - OH
ethanol
dimethyl ether
We learned about the contribution of scientists from all over the world to the development of the theory of the structure of the atom;
Explained the existence of isotopes on the example of hydrogen;
Considered the elementary composition of the atom on the example of phosphorus.
Lesson 1.
Atom is a complex particle
Target: to summarize the knowledge from the courses of physics and chemistry about the phenomena that prove the complexity of the structure of the atom, to acquaint students with the evolution of scientific views on the structure of the atom.
Know: features of the structure of the atom.
Be able to: describe the structure of an atom, characterize the particles that make up its composition.
During the classes
you remember that “atom” in Greek means “indivisible”, until the end of the 19th century this was considered true. But the discovery of the late nineteenth - early twentieth centuries. showed that the atom is complex.
Since it became clear that the atom is made up of smaller particles, scientists have been trying to
explain the structure of the atom, proposed models:
J. Thomson (1903) - an atom consists of a positive charge, uniformly distributed throughout the entire volume of the atom, and electrons oscillating inside this charge. This model has not been experimentally confirmed.
E. Rutherford (1911) - planetary or nuclear model of the atom:
Inside the atom is a positively charged nucleus, which occupies an insignificant part of the volume of the atom;
All the positive charge and almost all the mass of the atom is concentrated in the nucleus;
Electrons revolve around the nucleus, they neutralize the charge of the nucleus.
Rutherford's model was confirmed by experiments with thin metal plates irradiated with alpha particles.
But classical mechanics couldn't explain why the electrons don't lose energy as they spin and fall into the nucleus.
In 1913, N. Bohr supplemented the planetary model with postulates:
Electrons in an atom rotate in strictly defined closed orbits, without emitting or absorbing energy;
When electrons move from one orbit to another, energy is absorbed or released.
4. Modern quantum model of the structure of the atom:
The electron has a dual nature. Like a particle, an electron has a mass of 9.1x10 -28 g and a charge of 1.6x10 -19 C.
An electron in an atom does not move along a certain trajectory, but can be located in any part of the nuclear space. The probability of finding an electron in different parts of the circumnuclear space is not the same.
The space around the nucleus where the probability of finding an electron is greatest is calledorbital .
- The nucleus consists of nucleons - protons and neutrons. The number of protons in the nucleus is equal to the atomic number of the element, and the sum of the numbers of protons and neutrons is equal to the mass number of the atom.
This provision was formulated after the discovery by E. Rutherford in 1920 of the proton, and by J. Chadwick in 1932 of the neutron.
The different types of atoms are called nuclides. Nuclides are characterized by mass number A and nuclear charge Z.
Nuclides with the same Z but different A are called isotopes.(35 17 Cl and 37 17 Cl).
Nuclides with different Z but the same A are called isobars.(40 18 Ar and 40 19 K).
Exercise 1:
Draw the structure of the atom for the elements: iron, aluminum, barium, potassium, silicon.
Task 2
1. Determine the chemical element by the composition of its atom - 18 p +, 20 n 0, 18 e -:
a) F b) Ca c) Ar d) Sr
2. The total number of electrons in the chromium ion 24 Cr 3+ :
a) 21 b) 24 c) 27 d) 52
3. The maximum number of electrons occupying 3 s- orbital, is equal to:
a) 14 b) 2 c) 10 d) 6
4. Number of orbitals per f- sublevel:
a) 1 b) 3 c) 5 d) 7
5 . The smallest radius of an atom among the given elements has:
a) Mg b) Ca c) Si d) Cl
Homework: § 1. learn from a notebook, tasks 1-4.
