Who invented the atom. The world is wonderful

ATOM, the smallest particle of a substance that can undergo chemical reactions. Every substance has its own set of atoms. At one time it was believed that the atom is indivisible, however, it consists of a positively charged NUCLEAR, around which negatively charged electrons revolve. The nucleus (whose existence was established in 1911 by Ernst RUTHERFORD) consists of densely packed protons and neutrons. It occupies only a small part of the space inside the atom, however, it accounts for almost the entire mass of the atom. In 1913, Niels BOR suggested that electrons move in fixed orbits. Since then, research in QUANTUM MECHANICS has led to a new understanding of orbits: according to Heisenberg's UNCERTAINTY PRINCIPLE, the exact position and MOMENT of motion of a subatomic particle cannot be known simultaneously. The number of electrons in an atom and their arrangement determine the chemical properties of the element. When one or more electrons are added or taken away, an ion is created.

The mass of an atom depends on the size of the nucleus. It accounts for the largest fraction of the weight of an atom, since electrons weigh nothing. For example, the uranium atom is the heaviest naturally occurring atom. It has 146 neutrons, 92 protons, and 92 electrons. On the other hand, the lightest is the hydrogen atom, which has 1 proton and an electron. However, the uranium atom, although 230 times heavier than the hydrogen atom, is only three times larger in size. The weight of an atom is expressed in units of atomic mass and is denoted as u. Atoms are made up of even smaller particles called subatomic (elementary) particles. The main ones are protons (positively charged), neutrons (electrically neutral) and >lsktrons (negatively "charged). Accumulations of nrounons and neutrons form a Nucleus in the center of the atom of all >lsmston (with the exception of hydrogen, which has only one proton). "Electrons" spinning around! nuclei at some distance from it, commensurate with pa (measures of an atom. | (If, for example, the nucleus of a helium atom were the size of a tennis ball, then the electrons would be at a distance of 6 km from it. There are 112 different types of atoms, as many as elements on the periodic table. Atoms of elements differ in atomic number and atomic mass. NUCLEAR OF THE ATOM The mass of an atom is mainly due to the relatively dense nucleus. I (rotons and neutrons have a mass approximately 1K4 () times greater than electrons. Since the runs are charged positive, and neutrons are neutral, the nucleus of an atom is always positively charged. Since opposite charges mutually attract, the nucleus keeps electrons in their orbits. Runs and neutrons consist of even smaller particles, quarks. determines its chemical ignorance H oshichis from the planets of the solar system, neuropes revolve around the nucleus randomly, oiMiiMi no fixed distance from the nucleus, obraz-ivh "o Syulochki. The more energy the elek-ipon has. li "M, it can move away further, overcoming the attraction of a positively charged nucleus. In a neutral atom, the positive charge of the electrons balances the positive charge of the protons of the nucleus. Therefore, the removal or addition of one electron in the agome leads to the appearance of a charged ion. The electron shells are located at fixed distances from the nucleus depending on from their energy level.Each shell is numbered, counting from the nucleus.There are no more than seven shells on a gome, and each of them can contain only a certain number of electrons. If there is enough energy, the electron can jump from one shell to another, higher one. When it hits the lower shell again, it emits radiation in the form of a photon. An electron belongs to a class of particles called leptons, and its antiparticle is called a positron.

NUCLEAR CHAIN ​​REACTION. In a nuclear explosion, for example, ayumnoi oomba, a neutron strikes a 23b uranium nucleus (that is, a nucleus with a total number of protons and neutrons equal to ? 35). At: nom, the neutron is absorbed, and uranium is created. 236 It is very unstable and splits into two smaller nuclei, which releases a huge amount of energy and several neutrons. called critical conditions (the amount of uranium-235 exceeds the critical mass), then the number of neutron collisions will be sufficient for the reaction to develop at lightning speed, i.e. a chain reaction occurs. In a nuclear reactor, the heplo released during the EUM process is used to heat steam, which drives a turbine generator to generate electricity.

Scientific and technical encyclopedic dictionary.

See what "ATOM" is in other dictionaries:

atom an atom, and... Russian spelling dictionary

- (Greek atomos, from a negative part, and tome, tomos department, segment). An infinitely small indivisible particle, the totality of which makes up any physical body. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. ATOM Greek ... Dictionary of foreign words of the Russian language

atom- a m. atome m. 1. The smallest indivisible particle of matter. Atoms cannot be eternal. Cantemir About nature. Ampere believes that each indivisible particle of matter (atom) contains an inherent amount of electricity. DZ 1848 56 8 240. Let there be… … Historical Dictionary of Gallicisms of the Russian Language

- (from the Greek atomos - indivisible) the smallest constituent particles of matter that make up everything that exists, including the soul, formed from the finest atoms (Leucippus, Democritus, Epicurus). Atoms are eternal, they do not arise and do not disappear, being in a constant ... ... Philosophical Encyclopedia

Atom- Atom ♦ Atome Etymologically, an atom is an indivisible particle, or a particle subject only to speculative division; indivisible element (atomos) of matter. Democritus and Epicurus understand the atom in this sense. Modern scientists are well aware that this is ... ... Philosophical Dictionary of Sponville

- (from the Greek atomos indivisible) the smallest particle of a chemical element that retains its properties. In the center of the atom is a positively charged Nucleus, in which almost the entire mass of the atom is concentrated; electrons move around, forming electronic ... Big Encyclopedic Dictionary

Husband, Greek indivisible; matter in the extreme limits of its divisibility, an invisible speck of dust, from which all bodies are allegedly composed, every substance, as if from grains of sand. | An immeasurable, infinitely small speck of dust, an insignificant amount. | Chemists have a word ... ... Dahl's Explanatory Dictionary

Cm … Synonym dictionary

ATOM- (from the Greek atomos indivisible). The word A. is used in modern science in different senses. In most cases, A. call the limiting amount of chem. element, further fragmentation to horn leads to the loss of the individuality of the element, i.e. to a sharp ... ... Big Medical Encyclopedia

atom- atom Atom is a part of the speech, as the least bearer of the chemical powers of the singing chemical element. Vіdomo styles of species of atoms, sіlki of є chemical elements and їх іzotopіv. Electrically neutral, composed of nuclei and electrons. The radius of an atom ... ... Girnichiy encyclopedic dictionary

Books

• The hydrogen atom and non-Euclidean geometry, V.A. Fock. This book will be produced in accordance with your order using Print-on-Demand technology. Reproduced in the original author's spelling of the 1935 edition (publishing house "Publishing house ...
• The hydrogen atom is the simplest of the atoms. Continuation of the theory of Niels Bohr. Part 5. The frequency of photon radiation coincides with the average frequency of electron radiation in the transition, AI Shidlovsky. Bohr's theory of the hydrogen atom ("parallel" to the quantum mechanical approach) is continued along the traditional path of development of physics, where observable and unobservable quantities coexist in theory. For…

An atom, as a separate unit, is built from a nucleus with a positive charge and from electrons that carry a negative charge. That's what an atom is made of.

In its center is the nucleus, which is formed by even smaller particles - protons and neutrons. Relative to the radius of the entire atom, the radius of the nucleus is about a hundred thousand times smaller. The core density is extremely high.

A stable nucleus with a positive charge is a proton. A neutron is an elementary particle that does not have an electric charge, with a mass approximately equal to the mass of a proton. The mass of the nucleus consists, respectively, of the total mass of protons and neutrons, the totality of which in the composition of the nucleus is abbreviated as the nucleon. These nucleons in the nucleus are uniquely bound. The number of protons in an atom is equal to the number of protons in the atomic shell and, as a result, forms the basis for the chemical properties of the atom.

An electron, as the smallest particle of matter, carries an elementary negative electrical energy, constantly revolves around the nucleus in certain orbits, like the rotation of the planets around the Sun. Thus, the following answer can be given to the question of what an atom consists of: from elementary particles with positive, negative and neutral charges.

There is the following pattern: the size of an atom depends on the size of its electron shell, or the height of the orbit. As part of the answer to the question of what an atom consists of, it can be clarified that electrons can both be added to and removed from an atom. This circumstance turns the atom into a positive ion or, accordingly, into a negative one. And the process of transformation of an elementary chemical particle is called ionization.

A large amount of energy is concentrated in it, which can be released during nuclear reactions. Such reactions, as a rule, arise when atomic nuclei collide with other elementary particles or with the nuclei of other chemical elements. As a result, new nuclei are able to form. For example, the reaction is capable of carrying out the transition of a neutron into a proton, while a beta particle is removed from the nucleus of an atom, otherwise an electron.

A qualitative transition in the center of an atom from a proton to a neutron can be carried out in two ways. In the first case, a particle comes out of the nucleus with a mass that is equal to the mass of an electron, but with a positive charge, called a positron (the so-called positron decay). The second option involves the capture by the nucleus of an atom of one of the electrons closest to it from the K-orbit (K-capture). So chemical elements are transformed from one into another due to what the atom consists of.

There are such states of the formed nucleus when it has an excess of energy, in other words, it is in an excited state. In the case of a transition to a natural state, the nucleus releases excessive energy in the form of a portion of electromagnetic radiation with a very short wavelength - this is how gamma radiation is formed. The energy that is released during ongoing nuclear reactions finds practical application in a number of branches of science and industry.

Our world is fraught with a lot of secret and unsolved, because the physical and chemical processes are truly amazing. But scientists have constantly sought to understand the essence of matter, from which life in the universe is woven. This question often began to arise in mankind for a long time. This article will tell you what a simple atom is, what elementary particles it consists of, and how scientists discovered the existence of the smallest part of a chemical element.

What is an atom and how was it discovered?

An atom is the smallest part of a chemical element. Atoms of different elements differ in the number of protons and neutrons.

The first who began to seriously think about what all objects consist of were the ancient Greeks. By the way, the word "atom" came from the Greek language and in translation means "indivisible". The Greeks believed that sooner or later there would be a particle that could not be divided. But their reasoning was more speculative than scientific, so it cannot be said that this ancient people was the first to make great discoveries about the existence of small particles.

Consider the earliest ideas about what an atom is.

ancient greek philosopher Democritus assumed that the main parameters of any substance are shape and mass, and that any substance consists of small particles. Democritus gave an example with fire: if it burns, then the particles of which it consists are sharp. Water, on the contrary, is smooth, since it is able to flow. And the state of the particles of solid objects, in his opinion, is rough, since they are able to completely bond with each other. Democritus was also sure that the human soul consists of atoms.

An interesting fact: if until the 19th century only philosophers dealt with the issue of the atom, then John Dalton became the first experimenter who studied small particles. In the process of experiments, he found out that atoms have different masses, as well as different properties. By the way, it is much more interesting to study the arrangement of atoms in the molecules of specific substances if you observe the chemical reactions that occur during experiments. The works of Dalton, although they did not explain what the atom as a whole is, they gave parting words to some other scientists.

In 1904 John Thomson put forward an assumption about the model of the atom: the scientist believed that the atom consists of a positively charged substance, inside of which there are negatively charged corpuscles. The problem with the assumption is that Thompson sought to consider the spectral lines of the elements using his own model, but his experiments began to fail.

At the same time, the Japanese physicist Hataro Nagaoka admitted that the atom is similar to the planet Saturn: supposedly consists of a nucleus with a positive charge and electrons that revolve around it. But his model of the atom was not entirely correct.

In 1911 the scientist Rutherford put forward another assumption about the structure of the atom. The result of his hypotheses was stunning: now in modern science they rely heavily on the discovery of this physicist.

In 1913 Niels Bohr put forward a semi-classical theory of the structure of the atom, based on the works of Rutherford.

Creation of the Rutherford model of the atom

Let's take a look at this model because it details some of the properties of an atom. As mentioned earlier, Ernest Rutherford, the "father" of nuclear physics, began working on the model of the atom in 1911. The physicist began to get the desired result when he began to refute Thomson's model of the atom. The scientist came to the aid of an experiment on the scattering of alpha particles by Geiger and Marsden. The scientist suggested that the atom has a very small positively charged nucleus. These arguments helped to create a model of the atom, which is similar to the solar system, which is why it was given the name "Planetary Model of the Atom".

In the center of the atom is the nucleus, which contains almost the entire mass of the atom and has a positive charge. The nucleus is made up of protons and neutrons. Protons are elementary particles with a positive charge, and neutrons are elementary particles that do not have a charge. Electrons revolve around the nucleus, like the planets of the solar system.

Most of us studied the topic of the atom at school, in a physics lesson. If, nevertheless, you have forgotten what an atom consists of or are just starting to go through this topic, this article is just for you.

What is an atom

To understand what an atom is made of, you first need to understand what it is. The generally accepted thesis in the school curriculum in physics is that an atom is the smallest particle of any chemical element. Thus, atoms are in everything that surrounds us. Whether it is an animate or inanimate object, on the lower physiological and chemical layers, it is composed of atoms.

Atoms are part of a molecule. Despite this belief, there are elements that are smaller than atoms, such as quarks. The topic of quarks is not discussed either at school or at universities (with the exception of special cases). Quark is a chemical element that has no internal structure, i.e. much lighter in structure than an atom. At the moment, science knows 6 types of quarks.

What is an atom made of?

All the objects around us, as already mentioned, consist of something. There is a table and two chairs in the room. Each piece of furniture, in turn, is made of some material. In this case, wood. A tree is made up of molecules, and those molecules are made up of atoms. And there are an infinite number of such examples. But what is the atom itself made of?

An atom consists of a nucleus containing protons and neutrons. Protons are positively charged particles. Neutrons, as the name implies, are neutrally charged, i.e. have no charge. Around the nucleus of an atom is a field (electric cloud) in which electrons (negatively charged particles) move. The number of electrons and protons can differ from each other. It is this difference that is key in chemistry, when the question of belonging to some substance is studied.

An atom with a different number of the above particles is called an ion. As you might have guessed, an ion can be negative or positive. It is negative if the number of electrons exceeds the number of protons. Conversely, if there are more protons, the ion will be positive.

Atom in the view of ancient thinkers and scientists

There are some very interesting assumptions about the atom. Below will be a list:

• Democritus' suggestion. Democritus assumed that the property of a substance depends on the shape of its atom. Thus, if something has the property of a liquid, then this is due precisely to the fact that the atoms that make up this liquid are smooth. Based on the logic of Democritus, the atoms of water and, for example, milk are similar.
• planetary assumptions. In the 20th century, some scientists presented assumptions that the atom is a kind of planets. One of these assumptions was as follows: like the planet Saturn, the atom also has rings around the nucleus, along which electrons move (the nucleus is compared with the planet itself, and the electric cloud with the rings of Saturn). Despite the objective similarity with the proven theory, this version was refuted. Similar was Bohr-Rutherford's suggestion, which was later refuted as well.

Despite this, one can safely say that Rutherford made a big leap towards understanding the real essence of the atom. He was right when he said that the atom is similar to the nucleus, which is positive in itself, and atoms move around it. The only flaw in his model is that the electrons that are around the atom do not move in any particular direction. Their movement is chaotic. This has been proven and entered into science under the name of the quantum mechanical model.

An atom is the smallest chemically indivisible part of a chemical element, which is the carrier of its properties. The atom consists of electrons and the atomic nucleus, which in turn consists of uncharged neutrons, as well as positively charged protons. If the number of electrons and protons is the same, then the atom is electrically neutral. Otherwise, it has either a negative or a positive charge, in which case it is called an ion.

Atoms are classified according to the number of neutrons and protons in the nucleus: the number of neutrons determines whether it belongs to any isotope of a chemical element, the number of protons - directly to this element. Atoms of different types in different quantities, which are connected by some interatomic bonds, form molecules.

The concept of the atom was first formulated by ancient Greek and ancient Indian philosophers. In the 17th and 18th centuries, chemists were able to confirm this hypothesis, that some of the substances cannot be further broken down into smaller elements using special chemical methods, experimentally. But in the late 19th and early 20th centuries, physicists discovered subatomic particles, after which it became clear that the atom is not really an “indivisible particle.” In 1860, an international congress of chemists took place in the German city of Karlsruhe, at which a number of decisions were made on the definition of the concepts of atom and molecule. As a result, an atom is the smallest particle of a chemical element, which is part of complex and simple substances.

Atom Models

Thomson's model of the atom. He proposed to consider an atom as some positively charged body, inside which electrons are enclosed. This hypothesis was finally refuted by the famous scientist Rutherford after his famous experiment, in which he scattered alpha particles.

Pieces of matter. The ancient Greek scientist Democritus believed that the properties of any substance can be determined by its mass, shape, and similar characteristics of the atoms of which it is composed. For example, fire has sharp atoms, as a result of which it can be burned, but in solid bodies they are rough, which is why they adhere tightly to each other, while in water they are smooth, and therefore it can flow. Democti also believed that the human soul is made up of atoms.

Nagaoka's early planetary model of the atom. Physicists from Japan Hantaro Nagaoka in 1904 proposed a model of the atom, which was built in direct analogy with Saturn. In this model, electrons orbited around a small positive nucleus and they were combined into rings. But this model was wrong.

Bohr-Rutherford planetary model of the atom. Ernest Rutherford in 1911 conducted several experiments, after which he came to the conclusion that the atom is a kind of planetary system, where electrons move in orbits around a heavy positively charged nucleus, which is located in the center of the atom. But such a description contradicted classical electrodynamics. According to the latter, an electron, while moving with centripetal acceleration, must radiate some kind of electromagnetic waves, as a result of which it will lose some energy. His calculations indicated that the time it takes for an electron to fall onto a nucleus in such an atom is absolutely negligible.

Niels Bohr, in order to explain the stability of atoms, had to introduce a number of special postulates, which were reduced to the fact that the electron atom, when it is in certain energy states, does not radiate energy (“the Bohr-Rutherford model of the atom”). Bohr's postulates showed that classical mechanics is inapplicable for describing the properties of the atom and its definition. The subsequent study of atomic radiation led to the creation of such a branch of physics as quantum mechanics, which made it possible to explain a huge number of observed facts.

Quantum mechanical model of the atom

The modern model of the atom is a development of the planetary model. The nucleus of an atom contains uncharged neutrons and positively charged protons, and is surrounded by electrons that have a negative charge. But the concepts of quantum mechanics do not make it possible to assert that electrons move around the nucleus along at least somehow defined trajectories.
The chemical properties of an atom are described by quantum mechanics and determined by the configuration of their electron shell. The location of an atom in Mendeleev's table of periodic chemical elements is determined based on their electric charge of its nucleus, i.e. the number of protons, and the number of neutrons does not fundamentally affect the chemical properties. The bulk of the atom's mass is concentrated in the nucleus. The mass of an atom is measured in special atomic mass units, equal to.

Atom properties

Any two atoms that have the same number of protons belong to the same chemical element. Atoms with the same number of protons but different numbers of neutrons are called isotopes of that element. For example, hydrogen atoms contain one proton, but there are isotopes that do not contain neutrons, either one neutron (deuterium) or two neutrons (tritium). Starting with the hydrogen atom, which has one proton, and ending with the ununoctium atom, which contains 118 protons, the chemical elements form an uninterrupted natural series in terms of the number of protons in the nucleus. From the 83rd number of the periodic system, radioactive isotopes of elements begin.

The rest mass of an atom is expressed in atomic mass units (daltons). The mass of an atom is approximately equal to the product of the atomic mass unit and the mass number. The heaviest isotope is lead-208, which has a mass of 207.976 amu. eat.
The outer electron atomic shell, if it is not completely filled, is called the valence shell, and its electrons are called valence.