The notion that atoms are the smallest particles of matter first arose in ancient Greece. However, only at the end of the XVIII 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 indivisible "bricks" of which all matter is composed.
Attempts to explain the structure of the atom
Who proposed the first atomic model of atomic structure ? 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. In this case, the scientist assumed that the positive charge is distributed evenly throughout the volume of this ball, and inside it is a negatively charged core. All attempts by the scientist to explain the internal structure of the atom were unsuccessful. Ernest Rutherford is the one who proposed a nuclear model of the structure of the atom a few years after Thomson put forward his theory.
Research history
Using a study of electrolysis in 1833, Faraday was able to establish that the current in an electrolyte solution is a stream of charged particles, or ions. Based on these studies, he was able to determine the minimum charge of the 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 the question in scientific circles that all atoms can have the same nature. We see that before the nuclear model of the structure of the Rutherford atom was first proposed, a wide variety of equally important experiments were carried out by various scientists. They advanced the atomistic theory of the structure of matter forward.
First experiences
Rutherford is truly a brilliant scientist, because his discoveries turned upside down the idea of the structure of matter. In 1911, he was able to conduct 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 a scientist with the support of other researchers, however, the main role in the discovery nevertheless belonged to Rutherford.
Experiment
Using natural sources of 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. There was a slot in the gun, thanks to which all alpha particles fell on the lead screen. They could fly out only through the slot. In the path of this beam of radioactive particles were several more screens.
They separated particles that deviated from the previously given direction. A strictly focused stream of alpha particles hit the target . Rutherford used a thin sheet of gold foil as a target. After the particles fell on this sheet, they continued their movement and ultimately fell on the luminescent screen, which was installed behind this target. When alpha particles hit this screen, flashes were recorded, according to 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 experiments
Pupils and students who are interested in those who proposed a nuclear model of the structure of the atom should know: such experiments were carried out in physics before Rutherford. Their main idea was to collect as much information as possible on the structure of the atom from the deviations of the particles from the original trajectory. All these studies have led to the accumulation of a certain amount of information in science, provoked to think about the internal structure of the smallest particles.
Already at the beginning of the 20th century, scientists knew that the atom contained electrons with a negative charge. But among most researchers, the prevailing opinion was that the inside of the atom was 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.
Ingenious hunch
Rutherford noted that none of his predecessors had ever tried to determine whether alpha particles could deviate at very large angles from their path. The previous model, sometimes called among scientists “pudding with raisins” (since according to this model the electrons in an atom are distributed like raisins in a pudding), simply did not allow the existence of dense components of the structure inside the atom. None of the scientists even bothered to consider such an option. The researcher asked his student to re-equip the installation so that large deviations of particles from the trajectory were recorded - only to exclude such a possibility. What was the surprise of both the scientist and his student when it turned out that some particles were scattered at an angle of 180 about .
What is inside an atom?
We learned who proposed the nuclear model of the structure of the atom and what the experience of this scientist was. 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 atomic structure 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 - particles are arranged in increasing energy order. The researcher called the internal parts of atoms nuclei. The names introduced by the scientist are still used in science.
How to prepare for the lesson?
Those students who are interested in those who suggested a nuclear model of the atomic structure may show additional knowledge in the lesson. For example, you can talk about how Rutherford, after a long time after his experiments, liked to give an analogy for his discovery. Smuggling of weapons for the rebels, which is enclosed in bales of cotton, is being delivered to a South African country. How can customs officers determine where exactly the dangerous supplies are if the whole train is clogged with these bales? The customs officer can start shooting at bales, and where the bullets ricochet, the weapon is located. Rutherford emphasized that this was exactly what 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 atomic structure?
2. What was the meaning of the experiment?
3. The difference between the nuclear model and other models.
The Importance of Rutherford's Theory
The radical conclusions that Rutherford made from his experiments made many of his contemporaries doubt the truth of this model. Even Rutherford himself was no exception - he published the results of his research only two years after the discovery. Based on classical ideas about how microparticles move, he proposed a nuclear planetary model of the structure of the atom. In general, an atom has a neutral charge. Electrons move around the nucleus - just like planets revolve around the sun. This movement is due to the Coulomb forces. Currently, the Rutherford model has undergone significant refinement, but the discovery of the scientist does not lose its relevance today.