Which is smaller atom or electron. The world is beautiful

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 particle of a chemical element that retains all of its chemical properties. An atom consists of a positively charged nucleus and negatively charged electrons. The charge of the nucleus of any chemical element is equal to the product of Z by e, where Z is the serial number of this element in the periodic system of chemical elements, e is the value of the elementary electric charge.

Electron- this is the smallest particle of a substance with a negative electric charge e=1.6·10 -19 coulombs, taken as an elementary electric charge. Electrons, rotating around the nucleus, are located on the electron shells K, L, M, etc. K is the shell closest to the nucleus. The size of an atom is determined by the size of its electron shell. An atom can lose electrons and become a positive ion, or gain electrons and become a negative ion. The charge of an ion determines the number of electrons lost or gained. The process of turning a neutral atom into a charged ion is called ionization.

atomic nucleus(the central part of the atom) consists of elementary nuclear particles - protons and neutrons. The radius of the nucleus is about a hundred thousand times smaller than the radius of the atom. The density of the atomic nucleus is extremely high. Protons- These are stable elementary particles having a unit positive electric charge and a mass 1836 times greater than the mass of an electron. The proton is the nucleus of the lightest element, hydrogen. The number of protons in the nucleus is Z. Neutron is a neutral (not having an electric charge) elementary particle with a mass very close to the mass of a proton. Since the mass of the nucleus is the sum of the mass of protons and neutrons, the number of neutrons in the nucleus of an atom is A - Z, where A is the mass number of a given isotope (see). The proton and neutron that make up the nucleus are called nucleons. In the nucleus, nucleons are bound by special nuclear forces.

The atomic nucleus has a huge store of energy, which is released during nuclear reactions. Nuclear reactions occur when atomic nuclei interact with elementary particles or with the nuclei of other elements. As a result of nuclear reactions, new nuclei are formed. For example, a neutron can transform into a proton. In this case, a beta particle, i.e., an electron, is ejected from the nucleus.

The transition in the nucleus of a proton into a neutron can be carried out in two ways: either a particle with a mass equal to the mass of an electron, but with a positive charge, called a positron (positron decay), is emitted from the nucleus, or the nucleus captures one of the electrons from the nearest K-shell (K -capture).

Sometimes the formed nucleus has an excess of energy (it is in an excited state) and, passing into the normal state, releases excess energy in the form of electromagnetic radiation with a very short wavelength -. The energy released during nuclear reactions is practically used in various industries.

An atom (Greek atomos - indivisible) is the smallest particle of a chemical element that has its chemical properties. Each element is made up of certain types of atoms. The structure of an atom includes the kernel carrying a positive electric charge, and negatively charged electrons (see), forming its electronic shells. The value of the electric charge of the nucleus is equal to Z-e, where e is the elementary electric charge, equal in magnitude to the charge of the electron (4.8 10 -10 e.-st. units), and Z is the atomic number of this element in the periodic system of chemical elements (see .). Since a non-ionized atom is neutral, the number of electrons included in it is also equal to Z. The composition of the nucleus (see. Atomic nucleus) includes nucleons, elementary particles with a mass approximately 1840 times greater than the mass of an electron (equal to 9.1 10 - 28 g), protons (see), positively charged, and chargeless neutrons (see). The number of nucleons in the nucleus is called the mass number and is denoted by the letter A. The number of protons in the nucleus, equal to Z, determines the number of electrons entering the atom, the structure of the electron shells and the chemical properties of the atom. The number of neutrons in the nucleus is A-Z. Isotopes are called varieties of the same element, the atoms of which differ from each other in mass number A, but have the same Z. Thus, in the nuclei of atoms of different isotopes of one element there are a different number of neutrons with the same number of protons. When designating isotopes, the mass number A is written at the top of the element symbol, and the atomic number at the bottom; for example, isotopes of oxygen are denoted:

The dimensions of an atom are determined by the dimensions of the electron shells and for all Z are about 10 -8 cm. Since the mass of all the electrons of the atom is several thousand times less than the mass of the nucleus, the mass of the atom is proportional to the mass number. The relative mass of an atom of a given isotope is determined in relation to the mass of an atom of the carbon isotope C 12, taken as 12 units, and is called the isotopic mass. It turns out to be close to the mass number of the corresponding isotope. The relative weight of an atom of a chemical element is the average (taking into account the relative abundance of the isotopes of a given element) value of the isotopic weight and is called the atomic weight (mass).

An atom is a microscopic system, and its structure and properties can only be explained with the help of quantum theory, created mainly in the 20s of the 20th century and intended to describe phenomena on an atomic scale. Experiments have shown that microparticles - electrons, protons, atoms, etc. - in addition to corpuscular ones, have wave properties that manifest themselves in diffraction and interference. In quantum theory, a certain wave field characterized by a wave function (Ψ-function) is used to describe the state of micro-objects. This function determines the probabilities of possible states of a micro-object, i.e., it characterizes the potential possibilities for the manifestation of one or another of its properties. The law of variation of the function Ψ in space and time (the Schrödinger equation), which makes it possible to find this function, plays the same role in quantum theory as Newton's laws of motion in classical mechanics. The solution of the Schrödinger equation in many cases leads to discrete possible states of the system. So, for example, in the case of an atom, a series of wave functions for electrons is obtained corresponding to different (quantized) energy values. The system of energy levels of the atom, calculated by the methods of quantum theory, has received brilliant confirmation in spectroscopy. The transition of an atom from the ground state corresponding to the lowest energy level E 0 to any of the excited states E i occurs when a certain portion of energy E i - E 0 is absorbed. An excited atom goes into a less excited or ground state, usually with the emission of a photon. In this case, the photon energy hv is equal to the difference between the energies of an atom in two states: hv= E i - E k where h is Planck's constant (6.62·10 -27 erg·sec), v is the frequency of light.

In addition to atomic spectra, quantum theory has made it possible to explain other properties of atoms. In particular, valency, the nature of the chemical bond and the structure of molecules were explained, and the theory of the periodic system of elements was created.

An atom is made up of atomic nucleus and electrons. If the number of protons in the nucleus coincides with the number of electrons, then the atom as a whole is electrically neutral. Otherwise, it has some positive or negative charge and is called an ion. In some cases, atoms are understood only as electrically neutral systems in which the nuclear charge is equal to the total charge of electrons, thereby contrasting them with electrically charged ions.

Nucleus, which carries almost all (more than 99.9%) of the mass of an atom, consists of positively charged protons and uncharged neutrons bound together by strong interaction. Atoms are classified according to the number of protons and neutrons in the nucleus: the number of protons Z corresponds to the serial number of the atom in the periodic system and determines whether it belongs to a certain chemical element, and the number of neutrons N - to a certain isotope of this element. The Z number also determines the total positive electric charge (Ze) of the atomic nucleus and the number of electrons in a neutral atom, which determines its size.

Atoms of different types in different quantities, connected by interatomic bonds, form molecules.

Atom properties

By definition, any two atoms with the same number of protons in their nuclei belong to the same chemical element. Atoms with the same number of protons but different numbers of neutrons are called isotopes of a given element. For example, hydrogen atoms always contain one proton, but there are isotopes without neutrons (hydrogen-1, sometimes also called protium - the most common form), with one neutron (deuterium) and two neutrons (tritium). The known elements form a continuous natural series in terms of the number of protons in the nucleus, starting from the hydrogen atom with one proton and ending with the ununoctium atom, which has 118 protons in the nucleus. All isotopes of the elements of the periodic system, starting with number 83 (bismuth), are radioactive.

Weight

Since the largest contribution to the mass of an atom is made by protons and neutrons, the total number of these particles is called the mass number. The rest mass of an atom is often expressed in atomic mass units (a.m.u.), also called daltons (Da). This unit is defined as 1⁄12 of the rest mass of a neutral carbon-12 atom, which is approximately 1.66 x 10 e. m. The mass of an atom is approximately equal to the product of the mass number per atomic mass unit. The heaviest stable isotope is lead-208 with a mass of 207.9766521 amu. eat.

Since the masses of even the heaviest atoms in ordinary units (for example, in grams) are very small, moles are used in chemistry to measure these masses. One mole of any substance, by definition, contains the same number of atoms (approximately 6.022 1023). This number (Avogadro's number) is chosen in such a way that if the mass of an element is 1 a. e. m., then a mole of atoms of this element will have a mass of 1 g. For example, carbon has a mass of 12 a. e.m., so 1 mole of carbon weighs 12 g.

The size

Atoms do not have a distinct outer boundary, so their sizes are determined by the distance between the nuclei of neighboring atoms that have formed a chemical bond (Covalent radius) or by the distance to the farthest stable orbit of electrons in the electron shell of this atom (Radius of the atom). The radius depends on the position of the atom in the periodic table, the type of chemical bond, the number of nearby atoms (coordination number), and a quantum mechanical property known as spin. In the Periodic Table of Elements, the size of an atom increases as it moves from top to bottom in a column and decreases as it moves across a row from left to right. Accordingly, the smallest atom is a helium atom with a radius of 32 pm, and the largest is a cesium atom (225 pm). These dimensions are thousands of times smaller than the wavelength of visible light (400-700 nm), so atoms cannot be seen with an optical microscope. However, individual atoms can be observed using a scanning tunneling microscope.

The smallness of atoms is demonstrated by the following examples. A human hair is a million times thicker than a carbon atom. One drop of water contains 2 sextillion (2 1021) oxygen atoms, and twice as many hydrogen atoms. One carat of diamond with a mass of 0.2 g consists of 10 sextillion carbon atoms. If an apple could be enlarged to the size of the Earth, then the atoms would reach the original size of an apple.

Scientists from the Kharkov Institute of Physics and Technology presented the first images of the atom in the history of science. To obtain images, scientists used an electron microscope that captures radiation and fields (field-emission electron microscope, FEEM). Physicists sequentially placed dozens of carbon atoms in a vacuum chamber and passed through them an electric discharge of 425 volts. The radiation of the last atom in the chain to the phosphor screen made it possible to obtain an image of the electron cloud around the nucleus.

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). Clusters of prounons and neutrons form a Nucleus in the center of the atom of all >msmstone (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, while 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 agome, 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…

In 1913 the Danish physicist Niels Bohr proposed his theory of the structure of the atom. He took as a basis the planetary model of the atom, developed by the physicist Rutherford. In it, the atom was likened to the objects of the macrocosm - a planetary system, where the planets move in orbits around a large star. Similarly, in the planetary model of the atom, electrons move in orbits around the heavy nucleus located in the center.

Bohr introduced the idea of ​​quantization into the theory of the atom. According to it, electrons can only move in fixed orbits corresponding to certain energy levels. It was the Bohr model that became the basis for the creation of the modern quantum mechanical model of the atom. In this model, the nucleus of an atom, consisting of positively charged protons and uncharged neutrons, is also surrounded by negatively charged electrons. However, according to quantum mechanics, for an electron it is impossible to determine any exact trajectory or orbit of motion - there is only a region in which there are electrons with a similar energy level.

What is inside an atom?

Atoms are made up of electrons, protons and neutrons. Neutrons were discovered after the planetary model of the atom was developed by physicists. Only in 1932, while conducting a series of experiments, James Chadwick discovered particles that have no charge. The absence of charge was confirmed by the fact that these particles did not react in any way to the electromagnetic field.

The nucleus of an atom itself is formed by heavy particles - protons and neutrons: each of these particles is almost two thousand times heavier than an electron. Protons and neutrons are also similar in size, but protons have a positive charge and neutrons have no charge at all.

In turn, protons and neutrons are made up of elementary particles called quarks. In modern physics, quarks are the smallest, basic particle of matter.

The size of the atom itself is many times greater than the size of the nucleus. If an atom is enlarged to the size of a football field, then the size of its nucleus can be comparable to a tennis ball in the center of such a field.

In nature, there are many atoms that differ in size, mass and other characteristics. A group of atoms of the same type is called a chemical element. To date, more than a hundred chemical elements are known. Their atoms differ in size, mass, and structure.

Electrons inside an atom

Negatively charged electrons move around the nucleus of an atom, forming a kind of cloud. A massive nucleus attracts electrons, but the energy of the electrons themselves allows them to “run away” further from the nucleus. Thus, the greater the energy of an electron, the farther from the nucleus it is.

The value of the electron energy cannot be arbitrary, it corresponds to a well-defined set of energy levels in the atom. That is, the energy of an electron changes stepwise from one level to another. Accordingly, an electron can move only within a limited electron shell corresponding to a particular energy level - this is the meaning of Bohr's postulates.

Having received more energy, the electron “jumps” to a layer higher from the nucleus, losing energy, on the contrary, to a lower layer. Thus, the cloud of electrons around the nucleus is ordered in the form of several "cut" layers.

History of ideas about the atom

The very word "atom" comes from the Greek "indivisible" and goes back to the ideas of ancient Greek philosophers about the smallest indivisible part of matter. In the Middle Ages, chemists became convinced that certain substances could not be further broken down into their constituent elements. These smallest particles of matter are called atoms. In 1860, at the international congress of chemists in Germany, this definition was officially enshrined in world science.

In the late 19th and early 20th centuries, physicists discovered subatomic particles and it became clear that the atom is not in fact indivisible. Theories about the internal structure of the atom were immediately put forward, one of the first among which was the Thomson model or the “raisin pudding” model. According to this model, small electrons were inside a massive positively charged body, like raisins inside a pudding. However, the practical experiments of the chemist Rutherford refuted this model and led him to create a planetary model of the atom.

Bohr's development of the planetary model, along with the discovery of neutrons in 1932, formed the basis for the modern theory of the structure of the atom. The next stages in the development of knowledge about the atom are already connected with the physics of elementary particles: quarks, leptons, neutrinos, photons, bosons, and others.