Electricity: general concepts. Check your child! chemistry Flying particles of a substance that retain its properties are

For example, a water molecule is the smallest representative of a substance such as water.

Why don't we notice that substances are made up of molecules? The answer is simple: the molecules are so small that they are simply invisible to the human eye. So what size are they?

An experiment to determine the size of a molecule was carried out by the English physicist Rayleigh. Water was poured into a clean vessel, and a drop of oil was placed on its surface. The oil spread over the surface of the water and formed a round film. Gradually the area of ​​the film increased, but then the spreading stopped and the area stopped changing. Rayleigh suggested that the thickness of the film became equal to the size of one molecule. Through mathematical calculations it was established that the size of the molecule is approximately 16 * 10 -10 m.

Molecules are so small that small volumes of matter contain huge amounts of them. For example, one drop of water contains the same number of molecules as there are such drops in the Black Sea.

Molecules cannot be seen with an optical microscope. You can take photographs of molecules and atoms using an electron microscope, invented in the 30s of the 20th century.

Molecules of different substances differ in size and composition, but molecules of the same substance are always the same. For example, the water molecule is always the same: in water, in a snowflake, and in steam.

Although molecules are very small particles, they are also divisible. The particles that make up molecules are called atoms. Atoms of each type are usually designated by special symbols. For example, an oxygen atom is O, a hydrogen atom is H, and a carbon atom is C. In total, there are 93 different atoms in nature, and scientists have created about 20 more in their laboratories. The Russian scientist Dmitry Ivanovich Mendeleev ordered all the elements and placed them in the periodic table, which we will learn more about in chemistry lessons.

An oxygen molecule consists of two identical oxygen atoms, a water molecule consists of three atoms - two hydrogen atoms and one oxygen atom. By themselves, hydrogen and oxygen do not have the properties of water. On the contrary, water only becomes water when such a bond is formed.

The sizes of atoms are very small. For example, if you enlarge an apple to the size of the globe, the size of the atom will increase to the size of an apple. In 1951, Erwin Müller invented the ion microscope, which made it possible to see the atomic structure of a metal in detail.

In our time, unlike the times of Democritus, the atom is no longer considered indivisible. At the beginning of the 20th century, scientists managed to study its internal structure.

It turned out that an atom consists of a nucleus and electrons rotating around the nucleus. Later it turned out that core in its turn consists of protons and neutrons.

Thus, experiments are in full swing at the Large Hadron Collider - a huge structure built underground on the border between France and Switzerland. The Large Hadron Collider is a 30-kilometer closed tube through which hadrons (the so-called proton, neutron or electron) are accelerated. Having accelerated almost to the speed of light, the hadrons collide. The force of the impact is so great that the protons are “broken” into pieces. It is assumed that in this way it is possible to study the internal structure of hadrons

It is obvious that the further a person goes in studying the internal structure of matter, the greater difficulties he encounters. It is possible that the indivisible particle that Democritus imagined does not exist at all and particles can be divided ad infinitum. Research in this area is one of the fastest growing topics in modern physics.

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Electricity: general concepts

Electrical phenomena became known to man first in the formidable form of lightning - discharges of atmospheric electricity, then electricity obtained through friction (for example, skin on glass, etc.) was discovered and studied; finally, after the discovery of chemical current sources (galvanic cells in 1800), electrical engineering arose and quickly developed. In the Soviet state we witnessed the brilliant flourishing of electrical engineering. Russian scientists contributed greatly to such rapid progress.

However, it is difficult to give a simple answer to the question: “What is electricity?" We can say that “electricity is electrical charges and associated electromagnetic fields.” But such an answer requires detailed further explanation: “What are electric charges and electromagnetic fields?” We will gradually show how essentially complex the concept of “electricity” is, although extremely diverse electrical phenomena have been studied in great detail, and in parallel with their deeper understanding, the field of practical application of electricity has expanded.

The inventors of the first electric machines imagined electric current as the movement of a special electrical fluid in metal wires, but to create vacuum tubes it was necessary to know the electronic nature of electric current.

The modern doctrine of electricity is closely connected with the doctrine of the structure of matter. The smallest particle of a substance that retains its chemical properties is a molecule (from the Latin word “moles” - mass).

This particle is very small, for example, a water molecule has a diameter of about 3/1000,000,000 = 3/10 8 = 3*10 -8 cm and a volume of 29.7*10 -24.

To imagine more clearly how small such molecules are, what a huge number of them fit in a small volume, let us mentally carry out the following experiment. Let's somehow mark all the molecules in a glass of water (50 cm 3) and pour this water into the Black Sea. Let us imagine that the molecules contained in these 50 cm 3, evenly distributed throughout the vast oceans, which occupy 71% of the globe's area; Then let’s scoop up another glass of water from this ocean, at least in Vladivostok. Is there a probability of finding at least one of the molecules we labeled in this glass?

The volume of the world's oceans is enormous. Its surface is 361.1 million km 2. Its average depth is 3795 m. Therefore, its volume is 361.1 * 10 6 * 3.795 km 3, i.e. about 1,370 LLC LLC km 3 = 1,37*10 9 km 3 - 1,37*10 24 cm 3.

But at 50 cm 3 water contains 1.69 * 10 24 molecules. Consequently, after mixing, each cubic centimeter of ocean water will contain 1.69/1.37 labeled molecules, and about 66 labeled molecules will end up in our glass in Vladivostok.

No matter how small molecules are, they are made up of even smaller particles - atoms.

An atom is the smallest part of a chemical element, which is the carrier of its chemical properties. A chemical element is usually understood as a substance consisting of identical atoms. Molecules can form identical atoms (for example, a molecule of hydrogen gas H2 consists of two atoms) or different atoms (a molecule of water H20 consists of two hydrogen atoms H2 and an oxygen atom O). In the latter case, when molecules are divided into atoms, the chemical and physical properties of the substance change. For example, when the molecules of a liquid body, water, decompose, two gases are released - hydrogen and oxygen. The number of atoms in molecules varies: from two (in a hydrogen molecule) to hundreds and thousands of atoms (in proteins and high-molecular compounds). A number of substances, in particular metals, do not form molecules, that is, they consist directly of atoms not connected internally by molecular bonds.

For a long time, an atom was considered to be the smallest particle of matter (the name atom itself comes from the Greek word atomos - indivisible). It is now known that the atom is a complex system. Most of the mass of the atom is concentrated in its nucleus. The lightest electrically charged elementary particles - electrons - revolve around the nucleus in certain orbits, just as the planets revolve around the Sun. Gravitational forces hold the planets in their orbits, and electrons are attracted to the nucleus by electrical forces. Electrical charges can be of two different types: positive and negative. From experience we know that only opposite electric charges attract each other. Consequently, the charges of the nucleus and electrons must also have different signs. It is conventionally accepted to consider the charge of electrons to be negative and the charge of the nucleus to be positive.

All electrons, regardless of the method of their production, have the same electrical charges and a mass of 9.108 * 10 -28 G. Consequently, the electrons that make up the atoms of any element can be considered the same.

At the same time, the electron charge (usually denoted e) is elementary, i.e., the smallest possible electric charge. Attempts to prove the existence of smaller charges were unsuccessful.

The belonging of an atom to a particular chemical element is determined by the magnitude of the positive charge of the nucleus. Total negative charge Z electrons of an atom is equal to the positive charge of its nucleus, therefore, the value of the positive charge of the nucleus must be eZ. The Z number determines the place of an element in Mendeleev’s periodic table of elements.

Some electrons in an atom are in inner orbits, and some are in outer orbits. The former are relatively firmly held in their orbits by atomic bonds. The latter can relatively easily separate from an atom and move to another atom, or remain free for some time. These outer orbital electrons determine the electrical and chemical properties of the atom.

As long as the sum of the negative charges of the electrons is equal to the positive charge of the nucleus, the atom or molecule is neutral. But if an atom has lost one or more electrons, then due to the excess positive charge of the nucleus it becomes a positive ion (from the Greek word ion - moving). If an atom has captured excess electrons, then it serves as a negative ion. In the same way, ions can be formed from neutral molecules.

The carriers of positive charges in the nucleus of an atom are protons (from the Greek word “protos” - first). The proton serves as the nucleus of hydrogen, the first element in the periodic table. Its positive charge e + is numerically equal to the negative charge of the electron. But the mass of a proton is 1836 times greater than the mass of an electron. Protons, together with neutrons, form the nuclei of all chemical elements. The neutron (from the Latin word “neuter” - neither one nor the other) has no charge and its mass is 1838 times greater than the mass of the electron. Thus, the main parts of atoms are electrons, protons and neutrons. Of these, protons and neutrons are firmly held in the nucleus of an atom and only electrons can move inside the substance, and positive charges under normal conditions can only move together with atoms in the form of ions.

The number of free electrons in a substance depends on the structure of its atoms. If there are a lot of these electrons, then this substance allows moving electric charges to pass through it well. It is called a conductor. All metals are considered conductors. Silver, copper and aluminum are especially good conductors. If, under one or another external influence, the conductor has lost some of the free electrons, then the predominance of the positive charges of its atoms will create the effect of a positive charge of the conductor as a whole, that is, the conductor will attract negative charges - free electrons and negative ions. Otherwise, with an excess of free electrons, the conductor will be negatively charged.

A number of substances contain very few free electrons. Such substances are called dielectrics or insulators. They transmit electrical charges poorly or practically not. Dielectrics include porcelain, glass, hard rubber, most plastics, air, etc.

In electrical devices, electrical charges move along conductors, and dielectrics serve to direct this movement.

The smallest particle of a chemical element that can exist independently is called an atom.
An atom is the smallest particle of a chemical element, indivisible only in chemical terms.
An atom is the smallest particle of a chemical element that retains all the chemical properties of that element. Atoms can exist in a free state and in compounds with atoms of the same or other elements.
An atom is the smallest particle of a chemical element that can exist independently.
According to modern views, an atom is the smallest particle of a chemical element, possessing all its chemical properties. By connecting with each other, atoms form molecules, which are the smallest particles of a substance - carriers of all its chemical properties.
The previous chapter outlined our ideas about. atom - the smallest particle of a chemical element. The smallest particle of a substance is a molecule formed from atoms between which chemical forces, or chemical bonds, act.
The concept of electricity is inextricably linked with the concept of the structure of atoms - the smallest particles of a chemical element.
From chemistry and previous sections of physics, we know that all bodies are built from individual, very small particles - atoms and molecules. By atoms we mean the smallest particle of a chemical element. A molecule is a more complex particle consisting of several atoms. The physical and chemical properties of elements are determined by the properties of the atoms of these elements.
Decisive in the establishment of atomistic concepts in chemistry were the works of the English scientist John Dalton (1766 - 1844), who introduced into chemistry the term atom itself as the smallest particle of a chemical element; atoms of different elements, according to Dalton, have different masses and thus differ from each other.
An atom is the smallest particle of a chemical element, a complex system consisting of a central positively charged nucleus and a shell of negatively charged particles moving around the nucleus - electrons.
From chemistry and previous sections of physics we know that all bodies are built from individual, very small particles - atoms and molecules. Atoms are the smallest particles of a chemical element. A molecule is a more complex particle consisting of several atoms. The physical and chemical properties of elements are determined by the properties of the atoms of these elements.
From chemistry and previous sections of physics we know that all bodies are built from individual, very small particles - atoms and molecules. An atom is the smallest particle of a chemical element. A molecule is a more complex particle consisting of several atoms. The physical and chemical properties of elements are determined by the properties of the atoms of these elements.
Phenomena confirming the complex structure of the atom. The structure of an atom - the smallest particle of a chemical element - can be judged, on the one hand, by the signals that it itself sends in the form of rays and even particles, on the other, by the results of bombardment of atoms of matter by fast charged particles.
The idea that all bodies consist of extremely small and further indivisible particles - atoms - was widely discussed even before our era by ancient Greek philosophers. The modern idea of ​​atoms as the smallest particles of chemical elements capable of bonding into larger particles - molecules that make up substances, was first expressed by M. V. Lomonosov in 1741 in his work Elements of Mathematical Chemistry; These views were propagated by him throughout his entire scientific career. Contemporaries did not pay due attention to the works of M.V. Lomonosov, although they were published in publications of the St. Petersburg Academy of Sciences, received by all major libraries of that time.

The idea that all bodies consist of extremely small and further indivisible particles - atoms - was discussed back in Ancient Greece. The modern idea of ​​atoms as the smallest particles of chemical elements capable of bonding into larger particles - molecules that make up substances, was first expressed by M. V. Lomonosov in 1741 in his work Elements of Mathematical Chemistry; He propagated these views throughout his entire scientific career.
The idea that all bodies consist of extremely small and further indivisible particles - atoms - was widely discussed even before our era by ancient Greek philosophers. The modern idea of ​​atoms as the smallest particles of chemical elements capable of bonding into larger particles - molecules that make up substances, was first expressed by M. V. Lomonosov in 1741 in his work Elements of Mathematical Chemistry; He propagated these views throughout his entire scientific career.
The idea that all bodies consist of extremely small and further indivisible particles - atoms - was widely discussed by ancient Greek philosophers. The modern idea of ​​atoms as the smallest particles of chemical elements capable of bonding into larger particles - molecules that make up substances, was first expressed by M. V. Lomonosov in 1741 in his work Elements of Mathematical Chemistry; He propagated these views throughout his entire scientific career.
All kinds of quantitative calculations of the masses and volumes of substances taking part in chemical reactions are based on stoichiometric laws. In this regard, stoichiometric laws quite rightly relate to the basic laws of chemistry and are a reflection of the real existence of atoms and molecules that have a certain mass of the smallest particles of chemical elements and their compounds. Because of this, stoichiometric laws became a solid foundation on which modern atomic-molecular science was built.
All kinds of quantitative calculations of the masses and volumes of substances taking part in chemical reactions are based on stoichiometric laws. In this regard, stoichiometric laws quite rightly relate to the basic laws of chemistry and are a reflection of the real existence of atoms and molecules that have a certain mass of the smallest particles of chemical elements and their compounds. Because of this, stoichiometric laws became a solid foundation on which modern atomic-molecular science was built.
Phenomena confirming the complex structure of the atom. The structure of an atom - the smallest particle of a chemical element - can be judged, on the one hand, by the signals it sends in the form of rays and even particles, and on the other hand, by the results of bombardment of atoms of matter by fast charged particles.
It should be noted that the creation of quantum physics was directly stimulated by attempts to understand the structure of the atom and the patterns of emission spectra of atoms. As a result of experiments, it was discovered that at the center of the atom there is a small (compared to its size) but massive nucleus. An atom is the smallest particle of a chemical element that retains its properties. It gets its name from the Greek dtomos, which means indivisible. The indivisibility of the atom occurs in chemical transformations, as well as during collisions of atoms occurring in gases. And at the same time, the question has always arisen whether the atom consists of smaller parts.
The object of study in chemistry is chemical elements and their compounds. Chemical elements are collections of atoms with identical nuclear charges. In turn, an atom is the smallest particle of a chemical element that retains all its chemical properties.
The essence of this rejection of Avogadro's hypothesis was the reluctance to introduce a special concept of a molecule (particle), reflecting a discrete form of matter qualitatively different from atoms. Indeed: Dalton's simple atoms correspond to the smallest particles of chemical elements, and his complex atoms correspond to the smallest particles of chemical compounds. Because of these few cases, it was not worth breaking the entire system of views, which were based on one concept of the atom.
The considered stoichiometric laws form the basis for all kinds of quantitative calculations of the masses and volumes of substances taking part in chemical reactions. In this regard, stoichiometric laws quite rightly relate to the fundamental laws of chemistry. Stoichiometric laws are a reflection of the real existence of atoms and molecules, which, being the smallest particles of chemical elements and their compounds, have a very specific mass. Because of this, stoichiometric laws have become a solid foundation on which modern atomic-molecular science is built.

If you don’t yet know what a molecule is, then this article is just for you. Many years ago, people began to realize that each substance consists of individual small particles.