Lecture: Planetary model of the atom

The structure of the atom

The most accurate way to determine the structure of any substance is spectral analysis. The radiation of each atom of an element is exclusively individual. However, before understanding how spectral analysis occurs, let's figure out what structure an atom of any element has.

The first assumption about the structure of the atom was presented by J. Thomson. This scientist has been studying atoms for a long time. Moreover, it is he who owns the discovery of the electron - for which he received the Nobel Prize. The model that Thomson proposed had nothing to do with reality, but served as a strong enough incentive for Rutherford to study the structure of the atom. The model proposed by Thomson was called "raisin pudding".

Thomson believed that the atom is a solid ball with a negative electrical charge. To compensate for it, electrons are interspersed in the ball, like raisins. In sum, the charge of the electrons coincides with the charge of the entire nucleus, which makes the atom neutral.

During the study of the structure of the atom, it was found out that all atoms in solids make oscillatory motions. And, as you know, any moving particle radiates waves. That is why each atom has its own spectrum. However, these statements did not fit into the Thomson model in any way.

Rutherford's experience

To confirm or disprove Thomson's model, Rutherford proposed an experiment that resulted in the bombardment of an atom of some element by alpha particles. As a result of this experiment, it was important to see how the particle would behave.

Alpha particles were discovered as a result of the radioactive decay of radium. Their streams were alpha rays, each particle of which had a positive charge. As a result of numerous studies, it was determined that the alpha particle is like a helium atom, in which there are no electrons. Using current knowledge, we know that the alpha particle is the nucleus of helium, while Rutherford believed that these were helium ions.

Each alpha particle had tremendous energy, as a result of which it could fly at the atoms in question at high speed. Therefore, the main result of the experiment was to determine the particle deflection angle.

For the experiment, Rutherford used thin gold foil. He directed high-speed alpha particles at it. He assumed that as a result of this experiment, all particles would fly through the foil, and with small deviations. However, in order to find out for sure, he instructed his students to check if there were any large deviations in these particles.

The result of the experiment surprised absolutely everyone, because many particles not only deviated by a sufficiently large angle - some deflection angles reached more than 90 degrees.

These results surprised absolutely everyone, Rutherford said that it felt like a piece of paper was placed in the path of the projectiles, which did not allow the alpha particle to penetrate inside, as a result of which it turned back.

If the atom were really solid, then it should have some electric field, which slowed down the particle. However, the strength of the field was not enough to stop her completely, let alone push her back. This means that Thomson's model was refuted. So Rutherford started working on a new model.

To get this result of the experiment, it is necessary to concentrate the positive charge in a smaller amount, resulting in a larger electric field. Using the field potential formula, you can determine the required size of a positive particle that could repel an alpha particle in the opposite direction. Its radius should be of the order of maximum 10 -15 m. That is why Rutherford proposed the planetary model of the atom.

This model is named so for a reason. The fact is that inside the atom there is a positively charged nucleus, similar to the Sun in the solar system. Electrons revolve around the nucleus like planets. The solar system is arranged in such a way that the planets are attracted to the Sun with the help of gravitational forces, however, they do not fall on the surface of the Sun as a result of the available speed that keeps them in their orbit. The same thing happens with electrons - Coulomb forces attract electrons to the nucleus, but due to rotation, they do not fall on the surface of the nucleus.

One assumption of Thomson turned out to be absolutely correct - the total charge of electrons corresponds to the charge of the nucleus. However, as a result of a strong interaction, electrons can be knocked out of their orbit, as a result of which the charge is not compensated and the atom turns into a positively charged ion.

Very important information regarding the structure of the atom is that almost all the mass of the atom is concentrated in the nucleus. For example, a hydrogen atom has only one electron, whose mass is more than one and a half thousand times less than the mass of the nucleus.

The planetary model of the atom was proposed by E. Rutherford in 1910. The first studies of the structure of the atom were made by him with the help of alpha particles. Based on the results obtained in experiments on their scattering, Rutherford suggested that all the positive charge of the atom is concentrated in a tiny nucleus at its center. On the other hand, negatively charged electrons are distributed throughout the rest of its volume.

A little background

The first brilliant guess about the existence of atoms was made by the ancient Greek scientist Democritus. Since then, the idea of ​​the existence of atoms, the combinations of which give all the substances around us, has not left the imagination of people of science. From time to time, various representatives of it turned to it, but until the beginning of the 19th century, their constructions were just hypotheses, not supported by experimental data.

Finally, in 1804, more than a hundred years before the planetary model of the atom appeared, the English scientist John Dalton provided evidence for its existence and introduced the concept of atomic weight, which was its first quantitative characteristic. Like his predecessors, he conceived of atoms as the smallest pieces of matter, like solid balls, which cannot be divided into even smaller particles.

Discovery of the electron and the first model of the atom

Almost a century passed when, finally, at the end of the 19th century, also the Englishman J. J. Thomson, discovered the first subatomic particle, the negatively charged electron. Since atoms are electrically neutral, Thomson thought they must be composed of a positively charged nucleus with electrons scattered throughout its volume. Based on various experimental results, in 1898 he proposed his model of the atom, sometimes called "plums in a pudding", because the atom in it was represented as a sphere filled with some positively charged liquid, into which electrons were embedded, as "plums into the pudding. The radius of such a spherical model was about 10 -8 cm. The total positive charge of the liquid is symmetrically and uniformly balanced by the negative charges of the electrons, as shown in the figure below.

This model satisfactorily explained the fact that when a substance is heated, it begins to emit light. Although this was the first attempt to understand what an atom was, it failed to satisfy the results of the experiments carried out later by Rutherford and others. Thomson agreed in 1911 that his model simply could not answer how and why the scattering of α-rays observed in experiments occurs. Therefore, it was abandoned, and it was replaced by a more perfect planetary model of the atom.

How is the atom arranged anyway?

Ernest Rutherford provided an explanation of the phenomenon of radioactivity that won him a Nobel Prize, but his most significant contribution to science came later, when he established that the atom consists of a dense nucleus surrounded by orbits of electrons, just as the sun is surrounded by the orbits of planets.

According to the planetary model of an atom, most of its mass is concentrated in a tiny (compared to the size of the entire atom) nucleus. Electrons move around the nucleus, traveling at incredible speeds, but most of the volume of atoms is empty space.

The size of the nucleus is so small that its diameter is 100,000 times smaller than that of an atom. The diameter of the nucleus was estimated by Rutherford as 10 -13 cm, in contrast to the size of the atom - 10 -8 cm. Outside the nucleus, electrons revolve around it at high speeds, resulting in centrifugal forces that balance the electrostatic forces of attraction between protons and electrons.

Rutherford's experiments

The planetary model of the atom arose in 1911, after the famous experiment with gold foil, which made it possible to obtain some fundamental information about its structure. Rutherford's path to the discovery of the atomic nucleus is a good example of the role of creativity in science. His search began as early as 1899 when he discovered that certain elements emit positively charged particles that can penetrate anything. He called these particles alpha (α) particles (now we know they were helium nuclei). Like all good scientists, Rutherford was curious. He wondered if alpha particles could be used to find out the structure of an atom. Rutherford decided to aim a beam of alpha particles at a sheet of very thin gold foil. He chose gold because it can produce sheets as thin as 0.00004 cm. Behind a sheet of gold foil, he placed a screen that glowed when alpha particles hit it. It was used to detect alpha particles after they had passed through the foil. A small slit in the screen allowed the alpha particle beam to reach the foil after exiting the source. Some of them must pass through the foil and continue moving in the same direction, while the other part must bounce off the foil and be reflected at sharp angles. You can see the scheme of the experiment in the figure below.

What happened in Rutherford's experiment?

Based on J. J. Thomson's model of the atom, Rutherford assumed that the solid regions of positive charge filling the entire volume of gold atoms would deviate or bend the trajectories of all alpha particles as they passed through the foil.

However, the vast majority of the alpha particles passed right through the gold foil as if it wasn't there. They seemed to be passing through empty space. Only a few of them deviate from the straight path, as it was supposed at the beginning. Below is a plot of the number of particles scattered in the respective direction versus the scattering angle.

Surprisingly, a tiny percentage of the particles bounced back from the foil, like a basketball bouncing off a backboard. Rutherford realized that these deviations were the result of a direct collision between alpha particles and the positively charged components of the atom.

The nucleus takes center stage

Based on the negligible percentage of alpha particles reflected from the foil, we can conclude that all the positive charge and almost all the mass of the atom are concentrated in one small area, and the rest of the atom is mostly empty space. Rutherford called the area of ​​concentrated positive charge the nucleus. He predicted and soon discovered that it contained positively charged particles, which he named protons. Rutherford predicted the existence of neutral atomic particles called neutrons, but he failed to detect them. However, his student James Chadwick discovered them a few years later. The figure below shows the structure of the nucleus of a uranium atom.

Atoms consist of positively charged heavy nuclei surrounded by negatively charged extremely light particles-electrons rotating around them, and at such speeds that mechanical centrifugal forces simply balance their electrostatic attraction to the nucleus, and in this connection the stability of the atom is allegedly ensured.

The disadvantages of this model

Rutherford's main idea was related to the idea of ​​a small atomic nucleus. The assumption about the orbits of the electrons was pure conjecture. He did not know exactly where and how electrons revolve around the nucleus. Therefore, Rutherford's planetary model does not explain the distribution of electrons in orbits.

In addition, the stability of the Rutherford atom was possible only with the continuous movement of electrons in orbits without loss of kinetic energy. But electrodynamic calculations have shown that the movement of electrons along any curvilinear trajectories, accompanied by a change in the direction of the velocity vector and the appearance of a corresponding acceleration, is inevitably accompanied by the emission of electromagnetic energy. In this case, according to the law of conservation of energy, the kinetic energy of the electron must be very quickly spent on radiation, and it must fall on the nucleus, as shown schematically in the figure below.

But this does not happen, since atoms are stable formations. A typical scientific contradiction arose between the model of the phenomenon and the experimental data.

From Rutherford to Niels Bohr

The next major step forward in atomic history came in 1913, when the Danish scientist Niels Bohr published a description of a more detailed model of the atom. She determined more clearly the places where electrons could be. Although later scientists would develop more sophisticated atomic designs, Bohr's planetary model of the atom was basically correct, and much of it is still accepted today. It had many useful applications, for example, it is used to explain the properties of various chemical elements, the nature of their radiation spectrum and the structure of the atom. The planetary model and the Bohr model were the most important milestones that marked the emergence of a new direction in physics - the physics of the microworld. Bohr received the 1922 Nobel Prize in Physics for his contributions to our understanding of the structure of the atom.

What new did Bohr bring to the model of the atom?

While still a young man, Bohr worked in Rutherford's laboratory in England. Since the concept of electrons was poorly developed in Rutherford's model, Bohr focused on them. As a result, the planetary model of the atom was significantly improved. Bohr's postulates, which he formulated in his article "On the Structure of Atoms and Molecules", published in 1913, read:

1. Electrons can move around the nucleus only at fixed distances from it, determined by the amount of energy they have. He called these fixed levels energy levels or electron shells. Bohr envisioned them as concentric spheres, with a nucleus at the center of each. In this case, electrons with lower energy will be found at lower levels, closer to the nucleus. Those with more energy will be found at higher levels, farther from the core.

2. If an electron absorbs some (quite certain for a given level) amount of energy, then it will jump to the next, higher energy level. Conversely, if he loses the same amount of energy, he will return back to his original level. However, an electron cannot exist on two energy levels.

This idea is illustrated by a figure.

Energy portions for electrons

The Bohr model of the atom is actually a combination of two different ideas: Rutherford's atomic model with electrons revolving around the nucleus (essentially the planetary Bohr-Rutherford model of the atom), and Max Planck's idea of ​​quantizing the energy of matter, published in 1901. A quantum (plural - quanta) is the minimum amount of energy that can be absorbed or emitted by a substance. It is a kind of discretization step for the amount of energy.

If energy is compared to water and you want to add it to matter in the form of a glass, you cannot just pour water in a continuous stream. Instead, you can add it in small amounts, like a teaspoonful. Bohr believed that if electrons can only absorb or lose fixed amounts of energy, then they should only vary their energy by these fixed amounts. Thus, they can only occupy fixed energy levels around the nucleus that correspond to quantized increments of their energy.

So from the Bohr model grows a quantum approach to explaining what the structure of the atom is. The planetary model and the Bohr model were a kind of steps from classical physics to quantum physics, which is the main tool in the physics of the microcosm, including atomic physics.

They became an important step in the development of physics. Rutherford's model was of great importance. The atom as a system and the particles that make it up has been studied more accurately and in detail. This led to the successful development of such a science as nuclear physics.

Ancient ideas about the structure of matter

The assumption that the surrounding bodies are composed of the smallest particles was made in ancient times. The thinkers of that time represented the atom as the smallest and indivisible particle of any substance. They argued that there is nothing in the universe smaller than an atom. Such views were held by the great ancient Greek scientists and philosophers - Democritus, Lucretius, Epicurus. The hypotheses of these thinkers today are united under the name "ancient atomism".

Medieval performances

The times of antiquity have passed, and in the Middle Ages there were also scientists who made various assumptions about the structure of substances. However, the predominance of religious philosophical views and the power of the church at that period of history nipped in the bud any attempts and aspirations of the human mind to materialistic scientific conclusions and discoveries. As you know, the medieval Inquisition behaved very unfriendly with representatives of the scientific world of that time. It remains to be said that the then bright minds had an idea that came from antiquity about the indivisibility of the atom.

Research in the 18th and 19th centuries

The 18th century was marked by serious discoveries in the field of the elementary structure of matter. Largely thanks to the efforts of scientists such as Antoine Lavoisier, Mikhail Lomonosov and Independently of each other, they were able to prove that atoms really exist. But the question of their internal structure remained open. The end of the 18th century was marked by such a significant event in the scientific world as the discovery of the periodic system of chemical elements by D. I. Mendeleev. This was a truly powerful breakthrough of that time and lifted the veil over the understanding that all atoms have a single nature, that they are related to each other. Later, in the 19th century, another important step towards unraveling the structure of the atom was the proof that any of them contains an electron. The work of the scientists of this period prepared fertile ground for the discoveries of the 20th century.

Thomson experiments

The English physicist John Thomson proved in 1897 that the composition of atoms includes electrons with a negative charge. At this stage, the false ideas that the atom is the limit of the divisibility of any substance were finally destroyed. How did Thomson manage to prove the existence of electrons? In his experiments, the scientist placed electrodes in highly rarefied gases and passed an electric current. The result was cathode rays. Thomson carefully studied their features and found that they are a stream of charged particles that move at great speed. The scientist was able to calculate the mass of these particles and their charge. He also found out that they cannot be converted into neutral particles, since the electric charge is the basis of their nature. So were Thomson and the creator of the world's first model of the structure of the atom. According to her, an atom is a bunch of positively charged matter, in which negatively charged electrons are evenly distributed. This structure explains the general neutrality of atoms, since opposite charges balance each other. The experiments of John Thomson became invaluable for the further study of the structure of the atom. However, many questions remained unanswered.

Rutherford's research

Thomson discovered the existence of electrons, but he failed to find positively charged particles in the atom. corrected this misunderstanding in 1911. During experiments, studying the activity of alpha particles in gases, he discovered that there are positively charged particles in the atom. Rutherford saw that when rays pass through a gas or through a thin metal plate, a small number of particles sharply deviate from the trajectory of motion. They were literally thrown back. The scientist guessed that this behavior is due to a collision with positively charged particles. Such experiments allowed the physicist to create Rutherford's model of the structure of the atom.

planetary model

Now the scientist's ideas were somewhat different from the assumptions made by John Thomson. Their models of atoms also became different. allowed him to create a completely new theory in this area. The discoveries of the scientist were of decisive importance for the further development of physics. Rutherford's model describes an atom as a nucleus located in the center, and electrons moving around it. The nucleus has a positive charge, and the electrons have a negative charge. Rutherford's model of the atom assumed the rotation of electrons around the nucleus along certain trajectories - orbits. The discovery of the scientist helped explain the reason for the deviation of alpha particles and became the impetus for the development of the nuclear theory of the atom. In Rutherford's model of the atom, there is an analogy with the movement of the planets of the solar system around the sun. This is a very accurate and vivid comparison. Therefore, the Rutherford model, in which the atom moves around the nucleus in an orbit, was called planetary.

Works by Niels Bohr

Two years later, the Danish physicist Niels Bohr attempted to combine ideas about the structure of the atom with the quantum properties of the light flux. Rutherford's nuclear model of the atom was put by the scientist as the basis of his new theory. According to Bohr, atoms revolve around the nucleus in circular orbits. Such a trajectory of motion leads to the acceleration of electrons. In addition, the Coulomb interaction of these particles with the center of the atom is accompanied by the creation and consumption of energy to maintain the spatial electromagnetic field arising from the movement of electrons. Under such conditions, negatively charged particles must someday fall onto the nucleus. But this does not happen, which indicates the greater stability of atoms as systems. Niels Bohr realized that the laws of classical thermodynamics described by Maxwell's equations do not work in intraatomic conditions. Therefore, the scientist set himself the task of deriving new patterns that would be valid in the world of elementary particles.

Bohr's postulates

Largely due to the fact that Rutherford's model existed, the atom and its components were well studied, Niels Bohr was able to approach the creation of his postulates. The first of them says that an atom has at which it does not change its energy, while electrons move in orbits without changing their trajectory. According to the second postulate, when an electron moves from one orbit to another, energy is released or absorbed. It is equal to the difference between the energies of the previous and subsequent states of the atom. In this case, if the electron jumps to an orbit closer to the nucleus, then radiation occurs and vice versa. Despite the fact that the movement of electrons bears little resemblance to an orbital trajectory located strictly in a circle, Bohr's discovery provided an excellent explanation for the existence of a line spectrum. At about the same time, physicists Hertz and Frank, who lived in Germany, confirmed Niels Bohr's theory of the existence of stationary, stable states of the atom and the possibility of changing the values ​​of atomic energy.

Collaboration of two scientists

By the way, Rutherford could not determine for a long time Scientists Marsden and Geiger tried to double-check the statements of Ernest Rutherford and, as a result of detailed and thorough experiments and calculations, came to the conclusion that it is the nucleus that is the most important characteristic of the atom, and all its charge is concentrated in it. Later it was proved that the value of the charge of the nucleus is numerically equal to the ordinal number of the element in the periodic system of elements of D. I. Mendeleev. Interestingly, Niels Bohr soon met Rutherford and fully agreed with his views. Subsequently, scientists worked together for a long time in the same laboratory. Rutherford's model, the atom as a system consisting of elementary charged particles - all this Niels Bohr considered fair and put aside his electronic model forever. The joint scientific activity of scientists was very successful and bore fruit. Each of them delved into the study of the properties of elementary particles and made significant discoveries for science. Later, Rutherford discovered and proved the possibility of nuclear decomposition, but this is a topic for another article.

Planetary model of the atom

Planetary model of an atom: nucleus (red) and electrons (green)

Planetary model of the atom, or Rutherford model, - historical model of the structure of the atom, which was proposed by Ernest Rutherford as a result of an experiment with alpha particle scattering. According to this model, the atom consists of a small positively charged nucleus, in which almost the entire mass of the atom is concentrated, around which electrons move, just as the planets move around the sun. The planetary model of the atom corresponds to modern ideas about the structure of the atom, taking into account the fact that the movement of electrons is of a quantum nature and is not described by the laws of classical mechanics. Historically, Rutherford's planetary model succeeded Joseph John Thomson's "plum pudding model", which postulates that negatively charged electrons are placed inside a positively charged atom.

Rutherford proposed a new model for the structure of the atom in 1911 as a conclusion from an experiment on the scattering of alpha particles on gold foil, carried out under his leadership. During this scattering, an unexpectedly large number of alpha particles were scattered at large angles, which indicated that the scattering center was small and a significant electric charge was concentrated in it. Rutherford's calculations showed that a scattering center, positively or negatively charged, must be at least 3000 times smaller than the size of an atom, which at that time was already known and estimated to be about 10 -10 m. Since electrons were already known at that time, and their mass and charge are determined, then the scattering center, which was later called the nucleus, must have had the opposite charge to the electrons. Rutherford did not link the amount of charge to atomic number. This conclusion was made later. And Rutherford himself suggested that the charge is proportional to the atomic mass.

The disadvantage of the planetary model was its incompatibility with the laws of classical physics. If electrons move around the nucleus like a planet around the Sun, then their movement is accelerated, and, therefore, according to the laws of classical electrodynamics, they should radiate electromagnetic waves, lose energy and fall on the nucleus. The next step in the development of the planetary model was the Bohr model, postulating other, different from the classical, laws of electron motion. Completely the contradictions of electrodynamics were able to solve quantum mechanics.

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See what the "Planetary Model of the Atom" is in other dictionaries:

planetary model of the atom- planetinis atomo modelis statusas T sritis fizika atitikmenys: angl. planetary atom model vok. Planetenmodell des Atoms, n rus. planetary model of the atom, f pranc. modele planétaire de l'atome, m … Fizikos terminų žodynas

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Model (in science)- Model (French modèle, Italian modello, from Latin modulus measure, measure, sample, norm), 1) a sample that serves as a standard (standard) for serial or mass reproduction (M. car, M. clothing, etc. .), as well as the type, brand of any ... ...

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STRUCTURE OF THE ATOM- (see) is built from elementary particles of three types (see), (see) and (see), forming a stable system. The proton and neutron are a part of atomic (see), electrons form an electron shell. Forces act in the nucleus (see), thanks to which ... ... Great Polytechnic Encyclopedia

Atom- This term has other meanings, see Atom (meanings). Helium atom Atom (from other Greek ... Wikipedia

Rutherford Ernest- (1871 1937), English physicist, one of the creators of the theory of radioactivity and the structure of the atom, founder of a scientific school, foreign corresponding member of the Russian Academy of Sciences (1922) and honorary member of the USSR Academy of Sciences (1925). Born in New Zealand, after graduating from ... ... encyclopedic Dictionary

Άτομο

corpuscle- Helium atom Atom (another Greek ἄτομος indivisible) is the smallest part of a chemical element, which is the carrier of its properties. An atom consists of an atomic nucleus and an electron cloud surrounding it. The nucleus of an atom consists of positively charged protons and ... ... Wikipedia

corpuscles- Helium atom Atom (another Greek ἄτομος indivisible) is the smallest part of a chemical element, which is the carrier of its properties. An atom consists of an atomic nucleus and an electron cloud surrounding it. The nucleus of an atom consists of positively charged protons and ... ... Wikipedia

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The idea that atoms are the smallest particles of matter first arose in ancient Greece. However, only at the end of the 18th century, thanks to the work of such scientists as A. Lavoisier, M. V. Lomonosov and some others, it was proved that atoms really exist. However, in those days, no one wondered what their internal structure was. Scientists still regarded atoms as the indivisible "bricks" that make up all matter.

Attempts to explain the structure of the atom

Who proposed the nuclear model first of all scientists? The first attempt to create a model of these particles belonged to J. Thomson. However, it cannot be called successful in the full sense of the word. After all, Thomson believed that the atom is a spherical and electrically neutral system. At the same time, the scientist assumed that the positive charge is distributed evenly over the volume of this ball, and inside it there is a negatively charged nucleus. All attempts by the scientist to explain the internal structure of the atom were unsuccessful. Ernest Rutherford is the one who proposed the nuclear model of the structure of the atom a few years after Thomson put forward his theory.

Research History

With the help of the study of electrolysis in 1833, Faraday was able to establish that the current in the electrolyte solution is a stream of charged particles, or ions. Based on these studies, he was able to determine the minimum charge of an ion. Also an important role in the development of this direction in physics was played by the domestic chemist D. I. Mendeleev. It was he who first raised in scientific circles the question that all atoms can have the same nature. We see that before Rutherford's nuclear model of the structure of the atom was first proposed, a large number of equally important experiments were carried out by a variety of scientists. They advanced the atomistic theory of the structure of matter forward.

First experiences

Rutherford is a truly brilliant scientist, because his discoveries turned the idea of ​​\u200b\u200bthe structure of matter upside down. In 1911, he was able to set up an experiment with which researchers were able to look into the mysterious depths of the atom, to get an idea of ​​​​what its internal structure is. The first experiments were carried out by the scientist with the support of other researchers, but the main role in the discovery still belonged to Rutherford.

Experiment

Using natural sources of radioactive radiation, Rutherford was able to build a cannon that emitted a stream of alpha particles. It was a box made of lead, inside of which was a radioactive substance. The cannon had a slit through which all the alpha particles hit the lead screen. They could fly out only through the slot. Several more screens stood in the way of this beam of radioactive particles.

They separated particles that deviated from the previously set direction. A strictly focused target hit the target. Rutherford used a thin sheet of gold foil as a target. After the particles hit this sheet, they continued their movement and eventually hit the fluorescent screen, which was installed behind this target. When alpha particles hit this screen, flashes were recorded, by which the scientist could judge how many particles deviate from the original direction when they collide with the foil and what is the magnitude of this deviation.

Differences from previous experiences

Schoolchildren and students who are interested in those who proposed the nuclear model of the structure of the atom should know that similar experiments were carried out in physics before Rutherford. Their main idea was to collect as much information as possible about the structure of the atom from the deviations of particles from the original trajectory. All these studies led to the accumulation of a certain amount of information in science, provoked reflection on the internal structure of the smallest particles.

Already at the beginning of the 20th century, scientists knew that the atom contains electrons that have a negative charge. But among the majority of researchers, the prevailing opinion was that the atom from the inside is more like a grid filled with negatively charged particles. Such experiments made it possible to obtain a lot of information - for example, to determine the geometric dimensions of atoms.

genius guess

Rutherford noticed that none of his predecessors had ever tried to determine whether alpha particles could deviate at very large angles from their trajectory. The old model, sometimes called “raisin pudding” among scientists (because according to this model, the electrons in the atom are distributed like raisins in the pudding), simply did not allow the existence of dense structural components inside the atom. None of the scientists even bothered to consider this option. The researcher asked his student to re-equip the installation in such a way that large deviations of particles from the trajectory were also recorded - only in order to exclude such a possibility. Imagine the surprise of both the scientist and his student when it turned out that some particles fly apart at an angle of 180 o.

What's inside an atom?

We learned who proposed the nuclear model of the structure of the atom and what was the experience of this scientist. At that time, Rutherford's experiment was a real breakthrough. He was forced to conclude that inside the atom, most of the mass is enclosed in a very dense substance. The scheme of the nuclear model of the structure of the atom is extremely simple: inside is a positively charged nucleus.

Other particles, called electrons, revolve around this nucleus. The rest is several orders of magnitude less dense. The arrangement of electrons inside an atom is not chaotic - the particles are arranged in order of increasing energy. The researcher called the internal parts of atoms nuclei. The names that the scientist introduced are still used in science.

How to prepare for the lesson?

Those schoolchildren who are interested in those who suggested the nuclear model of the structure of the atom can show off additional knowledge in the lesson. For example, you can tell how Rutherford, long after his experiments, liked to give an analogy for his discovery. The South African country is smuggled with weapons for the rebels, which are enclosed in bales of cotton. How can customs officers determine exactly where dangerous supplies are if the entire train is full of these bales? The customs officer can start shooting at the bales, and where the bullets will ricochet, and there is a weapon. Rutherford stressed that this is how his discovery was made.

Students who are preparing to answer on this topic in the lesson, it is advisable to prepare answers to the following questions:

1. Who proposed the nuclear model of the structure of the atom?

2. What was the meaning of the experiment?

3. Difference of the nuclear model from other models.

Significance of Rutherford's theory

The radical conclusions that Rutherford drew from his experiments made many of his contemporaries doubt the validity of this model. Even Rutherford himself was no exception - he published the results of his research only two years after the discovery. Taking as a basis the classical ideas about how microparticles move, he proposed a nuclear planetary model of the structure of the atom. In general, the atom has a neutral charge. Electrons move around the nucleus, just like the planets revolve around the sun. This movement occurs due to the Coulomb forces. At the moment, Rutherford's model has undergone significant refinement, but the discovery of the scientist does not lose its relevance today.