Most of us studied the topic of the atom at school, in physics class. If you still forgot what an atom is made of or are just starting to study 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 school curriculum in physics is that an atom is smallest particle any chemical element. Thus, atoms are in everything that surrounds us. Whether animate or inanimate object, on the lower physiological and chemical layers, it consists 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 in schools or universities (except in special cases). Quark is a chemical element that does not have internal structure, i.e. its structure is much lighter than an atom. On this moment Science knows 6 types of quarks.
What does an atom consist of?
All 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 in this case- made of wood. A tree is made of molecules, and these molecules are made of atoms. And such examples can be given infinite set. But what does the atom itself consist 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 there is a field (electric cloud) in which electrons (negatively charged particles) move. The number of electrons and protons may differ from each other. It is this difference that is key in chemistry, when the question of belonging to a substance is studied.
An atom whose number of the above particles differs 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. And vice versa, if there are more protons, the ion will be positive.
The atom as imagined by ancient thinkers and scientists
There are some very interesting assumptions about the atom. Below is a list:
- Democritus' hypothesis. Democritus assumed that the properties of a substance depended 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 of which this liquid consists 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 suggested that the atom is a semblance of planets. One of these assumptions was as follows: like the planet Saturn, the atom also has rings around the nucleus through which electrons move (the nucleus is compared to the planet itself, and the electric cloud is compared to the rings of Saturn). Despite the objective similarity with the proven theory, this version was refuted. Bohr-Rutherford's assumption was similar, which was later also refuted.
Despite this, it can safely be said that Rutherford made a great leap forward in understanding real essence atom. He was right when he said that an atom is similar to a nucleus, which in itself is positive, 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 was proven and entered into science under the name of the quantum mechanical model.
Atom (from the Greek “indivisible”) - once the smallest particle of matter microscopic size, the smallest part of a chemical element that bears its properties. The components of an atom - protons, neutrons, electrons - no longer have these properties and form them together. Covalent atoms form molecules. Scientists study the features of the atom, and although they are already quite well studied, they do not miss the opportunity to find something new - in particular, in the field of creating new materials and new atoms (continuing the periodic table). 99.9% of the mass of an atom is in the nucleus.
Scientists from Radboud University discovered new mechanism magnetic storage of information in smallest unit substance: one atom. Although the proof of principle was demonstrated under very low temperatures, this mechanism promises to function even when room temperature. Thus, it will be possible to store thousands of times more information than is currently available on hard drives. The results of the work were published in Nature Communications.
ATOM(from the Greek atomos - indivisible), the smallest particle of a chemical. element, its holy. Each chem. An element corresponds to a collection of specific atoms. By bonding with each other, atoms of the same or different elements form more complex particles, e.g. . All the variety of chemicals. in-in (solid, liquid and gaseous) due to decomposition. combinations of atoms with each other. Atoms can also exist freely. state (in , ). The properties of the atom, including the most important ability of the atom to form chemicals. conn., are determined by the features of its structure.
general characteristics structure of the atom. An atom consists of a positively charged nucleus surrounded by a cloud of negatively charged ones. The dimensions of an atom as a whole are determined by the dimensions of its electron cloud and are large compared to the dimensions of the atomic nucleus (the linear dimensions of an atom are ~ 10~8 cm, its nucleus ~ 10" -10" 13 cm). The electron cloud of an atom does not have strictly defined boundaries, so the size of the atom means. degrees are conditional and depend on the methods of their determination (see). The nucleus of an atom consists of Z and N held nuclear forces(cm. ). Positive charge and negative. the charge is the same abs. magnitude and are equal to e = 1.60*10 -19 C; does not have electric power. charge. Nuclear charge +Ze - basic. characteristic of an atom that determines its belonging to a particular chemical. element. element in periodic periodic system () equal to the number in the core.
In an electrically neutral atom, the number in the cloud is equal to the number in the nucleus. However, under certain conditions, it can lose or add, turning respectively. in positive or deny. , eg. Li + , Li 2+ or O - , O 2- . When talking about atoms of a certain element, we mean both neutral atoms and that element.
The mass of an atom is determined by the mass of its nucleus; the mass (9.109*10 -28 g) is approximately 1840 times less than the mass or (1.67*10 -24 g), so the contribution to the mass of the atom is insignificant. Total number and A = Z + N called. . and nuclear charge are indicated respectively. superscript and subscript to the left of the element symbol, e.g. 23 11 Na. View of atoms of one element with a certain value
The stationary state of a one-electron atom is uniquely characterized by four quantum numbers: n, l, m l and m s. The energy of an atom depends only on n, and a level with a given n corresponds to a number of states differing in the values of l, m l, m s. States with given n and l are usually denoted as 1s, 2s, 2p, 3s, etc., where the numbers indicate the values of l, and the letters s, p, d, f and further in Latin correspond to the values d = 0, 1, 2 , 3, ... Number of dec. states with given p and d is equal to 2(2l+ 1) the number of combinations of values m l and m s. Total number of divers. states with given n equals 
, i.e., levels with values n = 1, 2, 3, ... correspond to 2, 8, 18, ..., 2n 2 decomp. . A level to which only one (one wave function) corresponds is called. non-degenerate. If a level corresponds to two or more , it is called. degenerate (see). In an atom, the energy levels are degenerate in the values of l and m l; degeneracy in m s occurs only approximately if the interaction is not taken into account. spin magnet moment with magnetic field caused by orbital motion in electric. nuclear field (see). This is a relativistic effect, small in comparison with the Coulomb interaction, but it is fundamentally significant, because leads to additional splitting of energy levels, which manifests itself in the form of the so-called. fine structure.
For given n, l and m l, the square of the modulus of the wave function determines the average distribution for the electron cloud in the atom. Diff. atoms differ significantly from each other in distribution (Fig. 2). Thus, at l = 0 (s-states) it is different from zero at the center of the atom and does not depend on the direction (i.e., spherically symmetric), for other states it is equal to zero at the center of the atom and depends on the direction. 
Rice. 2. Shape of electron clouds for various conditions atom
In multielectron atoms due to mutual electrostatic. repulsion significantly reduces their connection with the nucleus. For example, the energy of separation from He + is 54.4 eV; in a neutral He atom it is much less - 24.6 eV. For heavier atoms, the bond is ext. with a core even weaker. Important role plays a specific role in multielectron atoms. , associated with indistinguishability, and the fact that they obey, according to Krom, each one characterized by four quantum numbers cannot contain more than one. For a multi-electron atom, it makes sense to talk only about the entire atom as a whole. However, approximately, in the so-called. single-electron approximation, we can consider individual ones and characterize each one-electron state (a certain orbital described by the corresponding function) by a set of four quantum numbers 
n, l, m l and m s. The collection 2(2l+ 1) in a state with given n and l forms an electron shell (also called a sublevel, subshell); if all these states are occupied, the shell is called. filled (closed). A set of 2n 2 states with the same n, but different l forms an electronic layer (also called a level, shell). For n = 1, 2, 3, 4, ... layers are designated by the symbols K, L, M, N, ... The numbers in shells and layers when completely filled are given in the table: Between stationary states in an atom are possible. When moving from more high level energy E i to a lower E k the atom gives up energy (E i - E k), and during the reverse transition receives it. During radiative transitions, an atom emits or absorbs an electromagnetic quantum. radiation (photon). They are also possible when an atom gives or receives energy during interaction. with other particles with which it collides (for example, in) or is bound for a long time (in. Chemical properties are determined by the structure of the outer electron shells of atoms, in which they are bonded relatively weakly (binding energies from several eV up to several tens of eV). , increases; the maximum bond energy is in a closed shell. Therefore, atoms with one or several outer shells give them up in chemical regions. shells, usually accept them. normal conditions
do not enter into chemical districts. Internal structure shells of atoms, which are bound much more tightly (binding energy 10 2 -10 4 eV), manifests itself only during interaction. atoms with fast particles and photons. Such interactions determine the nature of the X-ray spectra and the scattering of particles (,) on atoms (see). The mass of an atom determines its physical properties. holy, like an impulse, kinetic. energy. From mechanical and related mag. and electric moments of the atomic nucleus depend on certain subtle physical factors. effects (depends on the frequency of radiation, which determines the dependence of the refractive index of the atom associated with it on it. The close connection between the optical properties of an atom and its electrical properties is especially clearly manifested in the optical spectra.
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Spanish literature for the article "ATOM": Karapetyants M. X., Drakin S. I., Structure, 3 ed., M., 1978; Shlo lye kiy E.V., Atomic physics, 7th ed., vol. 1-2, M., 1984. M. A. Elyashevich.
Page "ATOM" prepared using materials.
Modern man constantly hears phrases that contain derivatives of the word “atom”. This is energy, a power plant, a bomb. Some take it for granted, and some ask the question: “What is an atom?”
What does this word mean?
It has ancient Greek roots. Comes from “atomos”, which literally means “uncut”.
Someone already somewhat familiar with the physics of the atom will be indignant: “How is it “uncut”? It consists of some kind of particles!” The thing is that the name appeared when scientists did not yet know that atoms are not the smallest particles.
After experimental proof of this fact, it was decided not to change the usual name. And in 1860 they began to call "atom" the smallest particle, which has all the properties of the chemical element to which it belongs.
What is larger than an atom and smaller than it?
The molecule is always larger. It is formed from several atoms and is the smallest particle of matter.
But less - elementary particles. For example, electrons and protons, neutrons and quarks. There are a lot of them.
A lot has already been said about him. But it is still not very clear what an atom is.
What he really is?
The question of how to represent a model of an atom has long occupied scientists. Today, the one proposed by E. Rutherford and finalized by N. Bohr has been accepted. According to it, the atom is divided into two parts: the nucleus and the electron cloud.
Most of the mass of an atom is concentrated at its center. The nucleus consists of neutrons and protons. And the electrons in an atom are located quite great distance from the center. It turns out something similar to solar system. There is a core in the center, like the Sun, and electrons revolve around it in their orbits, like planets. That is why the model is often called planetary.
Interestingly, the nucleus and electrons occupy very little space compared to overall dimensions atom. It turns out that there is a small core in the center. Then emptiness. A very big void. And then a narrow strip of small electrons.
Scientists did not immediately arrive at this model of atoms. Before this, many assumptions were made that were refuted by experiments.
One of these ideas was the representation of the atom as a solid body that has positive charge. And it was proposed to place electrons in an atom throughout this body. This idea was put forward by J. Thomson. His model of the atom was also called "Raisin Pudding". The model very much resembled this dish.
But it was untenable because it could not explain some of the properties of the atom. That's why she was rejected.
Japanese scientist H. Nagaoka, when asked what an atom is, proposed such a model. In his opinion, this particle has a vague resemblance to the planet Saturn. There is a nucleus in the center, and electrons rotate around it in orbits connected in a ring. Although the model was not accepted, some of its provisions were used in the planetary diagram.
About the numbers associated with the atom
First about physical quantities. The total charge of an atom is always equal to zero. This is due to the fact that the number of electrons and protons in it is the same. And their charge is the same in magnitude and has opposite signs.
Situations often arise when an atom loses electrons or, conversely, attracts extra ones. In such situations they say that it has become an ion. And its charge depends on what happened to the electrons. If their number decreases, the charge of the ion is positive. When there are more electrons than required, the ion becomes negative.
Now about chemistry. This science, like no other, gives the greatest understanding of what an atom is. After all, even the main table that is studied in it is based on the fact that the atoms are located in it in in a certain order. It's about about the periodic table.
In it, each element is assigned a specific number, which is associated with the number of protons in the nucleus. It is usually denoted by the letter z.
The next value is the mass number. It is equal to the sum of protons and neutrons found in the nucleus of an atom. It is usually designated by the letter A.
Two specified numbers are related to each other by the following equality:
A = z + N.
Here N is the number of neutrons in the atomic nucleus.
Another important quantity is the mass of the atom. To measure it, a special value has been introduced. It is abbreviated: a.e.m. And it is read as an atomic mass unit. Based on this unit, the three particles that make up all the atoms of the Universe have masses:
These values are often needed when solving chemical problems.
Atom(from ancient Greek ἄτομος - indivisible) - a particle of a substance of microscopic size and mass, the smallest part of a chemical element, which is the bearer of its properties.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 turns out to be electrically neutral. IN otherwise he 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 charge of the nucleus is equal to the total charge of the electrons, thereby contrasting them with electrically charged ions.
Core, which carries almost the entire (more than 99.9%) mass of an atom, consists of positively charged protons and uncharged neutrons connected to each other by strong interaction. Atoms are classified by the number of protons and neutrons in the nucleus: the number of protons Z corresponds to serial number atom in periodic table and determines its belonging to some chemical element, and the number of neutrons N - to a specific 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 various types in different quantities, connected by interatomic bonds, form molecules.
Properties of the atom
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 amounts neutrons are called isotopes of this 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). Known elements form a continuous natural series according to the number of protons in the nucleus, starting with 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 table, starting with number 83 (bismuth), are radioactive.
Weight
Since protons and neutrons make the largest contribution to the mass of an atom, 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.), which is also called a dalton (Da). This unit is defined as 1⁄12 part of the rest mass of a neutral carbon-12 atom, which is approximately equal to 1.66 × 10−24 g. Hydrogen-1 is the lightest isotope of hydrogen and the atom with the smallest mass, has atomic weight about 1.007825 a. e.m. The mass of an atom is approximately equal to the product of the mass number times atomic unit mass Heaviest stable isotope- lead-208 with a mass of 207.9766521 a. eat.
Since the masses of even the heaviest atoms in ordinary units (for example, 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.
Size
Atoms do not have a clearly defined external 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 electron orbit in electron shell of this atom (Radius of the atom). The radius depends on the position of the atom in the periodic table, type 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 you move down a column and decreases as you move down 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 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 weighing 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 the apple.
Scientists from Kharkov Institute of Physics and Technology presented the first photographs of an atom in the history of science. To obtain images, scientists used an electron microscope that records radiation and fields (field-emission electron microscope, FEEM). Physicists sequentially placed dozens of carbon atoms in a vacuum chamber and passed them through electrical discharge at 425 volts. The radiation of the last atom in the chain onto a phosphorus screen made it possible to obtain an image of a cloud of electrons around the nucleus.