Discovery of radioactive transformations. The idea of atomic energy
The doctrine of phlogiston(1697 - 1703, Georg Stahl,) - a doctrine that suggested that there was a certain beginning of combustibility - phlogiston, which is contained in all substances that can burn with the release of a flame or turn into earthy substances when burned ("dross" or "lime" ). When burning or calcining such substances, phlogiston is released. The more phlogiston a substance contains, the more it is capable of burning.
Johann Becher(1635 - 1682) - German chemist and physician. Arguing about the composition of inorganic substances, he suggested that they consist of water and three earths: "mercury", "glassy" and "combustible". According to Becher, combustible earth, which he called "fat earth", is released during combustion; the body is the more combustible, the more it contains "fat earth".
Georg Stahl(1659 - 1734) - German chemist and physician, who worked for a long time as a professor of medicine in Jena and Halle. Stahl's ideas are expounded by him in the works "Becherov Example", "Foundations of Dogmatic and Experimental Chemistry", etc. Stahl also owns works on mining and metallurgy. Most likely, it was Stahl's industrial knowledge that largely contributed to the development of the theory of phlogiston.
6. Who and when created the oxygen theory of combustion? what is its essence and significance in the history of chemistry?
Oxygen combustion theory I (1774 - 1780, Antoine Lavoisier) - the doctrine that in combustion processes oxygen combines with combustible bodies and increases their weight; metal scales are not simple bodies (as in the theory of phlogiston), but compounds of metals with oxygen.
Carl Scheele(1742 - 1786) - Swedish chemist and pharmacist, one of the best experimenters of his time. In 1772, he singled out "fiery air" (oxygen) and described its properties, but these studies were published only in 1777. Until the end of his life, he remained a supporter of the phlogiston theory.
Joseph Priestley(1733 - 1804) - English chemist, philosopher and theologian. The research is related to the field of pneumatic chemistry. In 1774, he discovered "dephlogisticated air" (oxygen), having obtained it by heating mercury oxide. In theoretical views adhered to the theory of phlogiston.
Antoine Laurent Lavois e (1743 - 1794) - French. He created a well-equipped chemical laboratory at his own expense. He introduced strict quantitative methods into chemical practice, in particular the method of accurate weighing, thanks to which he came to the conclusion that the mass of substances in combustion processes is conserved. He established the ability of oxygen to combine with phosphorus and sulfur during combustion and metals during roasting. Lavoisier proved the complex composition of air. By 1780, he had laid the foundations of the oxygen theory, correctly explaining the processes of combustion and oxidation. Lavoisier later showed that water is a combination of oxygen and hydrogen ("combustible air"). Applied physico-chemical methods in biology. Executed by the verdict of the revolutionary tribunal.
7. When was the atomic-molecular doctrine created? what is its essence? Which of the chemists made the main contribution to its formation?
Concepts: "Chemical atomistics"Dalton. Matter consists of atoms; atoms are characterized by atomic weight; the law of multiple ratios is fulfilled . Electrochemical dualistic theory Berzelius - each chemical compound consists of two parts with different electrical polarity, the forces of chemical affinity are electrical in nature. The concept of "vitalism"- all substances that make up the organisms of animals and plants are formed in them under the influence of "life force". Atomic-molecular doctrine- the concept of a molecule as the smallest amount of a substance that enters into a chemical interaction, and consisting of the same or different atoms (works by Avogadro, Cannizzaro).
John Dalton(1766 - 1844) - English chemist and physicist. In 1803 -1804. put forward and substantiated the theory of atomic structure or chemical atomistics.
Jene Jacob Berzelius(1779 - 1848) - Swedish chemist. At 31, President of the Swedish Academy of Sciences. Experimentally verified and proved the reliability of the laws of composition constancy and multiple ratios in relation to inorganic oxides and organic compounds, Determined the atomic weight of 45 elements. Proposed a system of chemical symbols for designating elements that have been preserved in modern chemistry. Author of the electrochemical dualistic theory.
Amedeo Avogadro(1776 - 1856) - Italian physicist and chemist In 1811 he discovered Avogadro's law. Created a method for determining molecular weights. Established the quantitative atomic composition of the molecules of many substances (for example, hydrogen, oxygen, water). The results of Avogadro's work on molecular theory were recognized only after his death.
Stanislao Cannizzaro(1826 - 1910) - Italian chemist, one of the founders of the atomic-molecular theory. The main contribution to chemistry lies in the system of basic chemical concepts he proposed - "atom", "molecule" and "equivalent".
Topic: Radioactivity, alpha, beta, gamma radiation, displacement rule, half-life, law of radioactive decay. Purpose: To acquaint students with the historical chronology of the discovery of the phenomenon of natural radioactivity and the properties of radioactive radiation. To reveal the nature of radioactive decay and its laws. To develop the ability to analyze scientific material, research, using additional literature. To cultivate personal responsibility for what is happening around, sensitivity and humanity. Lesson objectives Educational objectives: to explain and reinforce new material, to introduce the history of the discovery, to show a presentation on the topic of the lesson Developmental objectives: to activate the mental activity of students in the lesson; to realize successful mastery of new material, to develop speech, the ability to draw conclusions. Educational tasks: to interest and captivate the topic of the lesson; create a personal situation of success; conduct a collective search to collect materials on radiation, create conditions for the development of the ability of schoolchildren to structure information. Equipment and materials: Sign of radioactive danger; portraits of scientists, handouts, reference books, projector, student abstracts, presentation. Type of lesson: lesson learning new material. Concepts and definitions: radioactivity, α-, β-particles, γ-radiation, half-life, radioactive series, radioactive transformation, laws of radioactive decay. "Only by understanding nature, a person will understand himself" R. Edberg (Swedish writer) Course of the lesson I. Organizational moment. Greeting students. II. Motivation of educational activity of students. Announcement of the topic of the lesson, assignments and expected results. Man fought for his existence for thousands of years, survived epidemics, famines, fifteen thousand wars, which she herself unleashed. She survived and always believed in a better life. For the sake of this man developed science, culture, medicine, new social systems. And now, through our erroneous moral principles, spiritual impoverishment, degradation of ecological consciousness and conscience, we again found ourselves on the threshold of a new, almost more terrible stage of survival. Radiation is unusual rays that are not visible to the eye and generally cannot be felt in any way, but which can even penetrate walls and penetrate a person. III. The stage of preparation for the study of a new topic Updating the existing knowledge of students in the form of checking homework and a cursory frontal survey of students. 1. What does the word "atom" mean? 2. Who introduced this concept into physics? 2 3. What does an atom consist of? 3 4. What is the structure of the atomic nucleus? What is a nucleon? 4 5. What is an electron? What is its charge? 6. How do nuclear forces differ from electrical and gravitational ones? 7. Thomson's model of the atom. 8. Planetary model of the atom. 9. What is the essence of Rutherford's experience? IV. Creation of a problem situation. Show sign of radioactive hazard. Answer the question: "What does this sign mean? What is the danger of radioactive radiation?" "There is nothing to be afraid of - you just need to understand the unknown" Maria Sklodowska-Curie. V. Stage of knowledge acquisition. 1) Student's messages. Discovery of radioactivity by Henri Becquerel. The discovery of radioactivity was due to a happy accident. Becquerel studied the luminescence of substances previously irradiated with sunlight for a long time. He wrapped the photographic plate in thick black paper, placed grains of uranium salt on top, and exposed it to bright sunlight. After developing, the photographic plate turned black in those areas where the salt lay. Becquerel thought that the radiation of uranium arises under the influence of sunlight. But one day, in February 1896, he failed to conduct another experiment due to cloudy weather. Becquerel put the record back in a drawer, placing on top of it a copper cross covered with uranium salt. Having developed the plate, just in case, two days later, he found blackening on it in the form of a distinct shadow of a cross. This meant that uranium salts spontaneously, without any external influences, create some kind of radiation. Intensive research began. Soon, Becquerel established an important fact: the intensity of radiation is determined only by the amount of uranium in the preparation, and does not depend on which compounds it is included in. Therefore, radiation is inherent not in compounds, but in the chemical element uranium. Then a similar quality was discovered in thorium. Slide number 1 Becquerel Antoine Henri French physicist. He graduated from the Polytechnic School in Paris. The main works are devoted to radioactivity and optics. In 1896 he discovered the phenomenon of radioactivity. In 1901, he discovered the physiological effect of radioactive radiation. Becquerel was awarded the Nobel Prize in 1903 for his discovery of the natural radioactivity of uranium. (1903, together with P. Curie and M. Sklodowska-Curie). 2) Student's messages. Discovery of radium and polonium. In 1898, other French scientists Marie Sklodowska-Curie and Pierre Curie isolated two new substances from the uranium mineral, much more radioactive than uranium and thorium. So two previously unknown radioactive elements were discovered - polonium and radium. It was exhausting work, for four long years the couple almost did not leave their damp and cold barn. Polonium (Po-84) was named after Mary's homeland, Poland. Radium (Ra-88) - radiant, the term radioactivity was proposed by Maria Sklodowska. All elements with serial numbers greater than 83 are radioactive, i.e. located in the periodic table after bismuth. For 10 years of joint work, they have done a lot to study the phenomenon of radioactivity. It was a selfless work in the name of science - in a poorly equipped laboratory and in the absence of the necessary funds, the researchers received the preparation of radium in 1902 in the amount of 0.1 g. To do this, they took 45 months of hard work there and more than 10,000 chemical liberation and crystallization operations. No wonder Mayakovsky compared poetry with the extraction of radium: "Poetry is the same extraction of radium. A gram of extraction, a year of work. You exhaust a single word for the sake of a thousand tons of verbal ore." In 1903, the Curies and A. Becquerel were awarded the Nobel Prize in Physics for their discovery in the field of radioactivity. The phenomenon of spontaneous transformation of unstable nuclei of atoms into the nuclei of other atoms with the emission of particles and radiation of energy is called natural radioactivity. Slide No. 2 Maria Sklodowska-Curie - Polish and French physicist and chemist, one of the founders of the theory of radioactivity was born on November 7, 1867 in Warsaw. She is the first female professor at the University of Paris. For studies of the phenomenon of radioactivity in 1903, together with A. Becquerel, she received the Nobel Prize in Physics, and in 1911 for obtaining radium in the metallic state - the Nobel Prize in Chemistry. She died of leukemia on July 4, 1934. Slide No. 3 - Pierre Curie - French physicist, one of the creators of the theory of radioactivity. Opened (1880) and investigated piezoelectricity. Studies on crystal symmetry (Curie principle), magnetism (Curie law, Curie point). Together with his wife, M. Sklodowska-Curie, he discovered (1898) polonium and radium and studied radioactive radiation. Introduced the term "radioactivity". Nobel Prize (1903, jointly with Sklodowska-Curie and A. A. Becquerel). Slide No. 4 3) Student's messages The complex composition of radioactive radiation. In 1899, under the guidance of the English scientist E. Rutherford, an experiment was conducted that made it possible to detect the complex composition of radioactive radiation. As a result of an experiment conducted under the guidance of an English physicist, it was found that the radioactive radiation of radium is inhomogeneous, i.e. it has a complex structure. Slide number 5. Rutherford Ernst (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). Director of the Cavendish Laboratory (since 1919). Opened (1899) alpha and beta rays and established their nature. Created (1903, together with F. Soddy) the theory of radioactivity. He proposed (1911) a planetary model of the atom. Carried out (1919) the first artificial nuclear reaction. Predicted (1921) the existence of the neutron. Nobel Prize (1908). Slide No. 6 A classic experiment that made it possible to detect the complex composition of radioactive radiation. The radium preparation was placed in a lead container with a hole. A photographic plate was placed opposite the hole. A strong magnetic field acted on the radiation. Almost 90% of known nuclei are unstable. Radioactive nuclei can emit particles of three types: positively charged (α-particles - helium nuclei), negatively charged (β-particles - electrons) and neutral (γ-particles - quanta of short-wave electromagnetic radiation). The magnetic field allows these particles to be separated. 4) Penetrating power α .β. γ radiation Slide No. 7 α-rays have the lowest penetrating power. A layer of paper 0.1 mm thick is no longer transparent for them. . β-rays are completely blocked by an aluminum plate several mm thick. . γ-rays, when passing through a 1 cm layer of lead, reduce the intensity by 2 times. 5) Physical nature of α .β. γ-radiation Slide № 8 γ-radiation electromagnetic waves 10-10-10-13m β-beams are a stream of electrons moving at speeds close to the speed of light. α-rays of the nucleus of the helium atom (brief description of Rutherford's research) Rutherford measured the ratio of particle charge to mass by deflection in a magnetic field. I measured the charge emitted by the particles of the source with an electrometer, and measured their number with a Geiger counter. Rutherford installed. that for each of the two elementary charges there are two atomic mass units. That is, the α-particle is the nucleus of the helium atom. 6) The displacement rule. Slide #9 Alpha decay. During alpha decay, the nucleus emits one α-particle, and from one chemical element another is formed, located two cells to the left in the periodic system of Mendeleev: Slide No. 10 Beta decay. During beta decay, one electron is emitted, and one chemical element is formed the other, located one cell to the right: In beta decay, another particle, called an electron antineutrino, flies out of the nucleus. This particle is denoted by the symbol * When neutral γ-quanta are emitted by the nuclei of atoms, nuclear transformations do not occur. The emitted γ-quantum carries away the excess energy of the excited nucleus; the number of protons and neutrons in it remain unchanged. The present model demonstrates various types of nuclear transformations. Nuclear transformations arise both as a result of the processes of radioactive decay of nuclei, and as a result of nuclear reactions accompanied by fission or synthesis of nuclei. Finish recording the decay 1. 2. 3. 4. 7) The law of radioactive decay. Slide. № 11 The time for which half of the initial number of radioactive atoms decays is called the half-life. During this time, the activity of the radioactive substance is halved. The half-life is the main value. determining the rate of radioactive decay. The shorter the half-life. the less time the atoms live, the faster the decay occurs. For different substances, the half-life has different values. Slide. No. 12 The law of radioactive decay was established by F. Soddy. The formula is used to find the number of undecayed atoms at any given time. Let at the initial moment of time the number of radioactive atoms N0. At the end of the half-life they will be N0./2. After t=nT there will be N0/2n VI. Stage of consolidation of new knowledge. Task 1. The amount of radioactive radon decreased by 8 times in 11.4 days. What is the half-life of radon? Given: t=11.4 days T-? ; Answer: T= 3.8 days. Task2. The half-life (radon) is 3.8 days. After what time will the mass of radon decrease by 4 times? Given: T=3.8 days; t-?T=2T=7.6 days Test. "Radioactivity" (Each student receives). Option 1 1. Which of the following scientists called the phenomenon of spontaneous emission radioactivity? A. The Curie spouses B. Rutherford S. Becquerel 2. -beams represent .... A. electron flow B. flow of helium nuclei C. electromagnetic waves 3. As a result of decay, the element shifts: A. one cell to the end of the system B. two cells to the beginning of the periodic system C. one cell to the beginning of the periodic system 4. The time during which half of the radioactive atoms decay is called ... A. decay time B. half-life C. decay period 5. There is 109 atoms of the radioactive isotope of iodine 53128I, its half-life is 25 min. Approximately what number of isotope nuclei will remain undecayed after 50 minutes? A. 5108 B. 109 C. 2.5108 Option 2 1. Which of the following scientists is the discoverer of radioactivity? A. The Curies B. Rutherford S. Becquerel 2. - the rays represent ... A. the flow of electrons B. the flow of helium nuclei C. electromagnetic waves 3. As a result - the decay of the element is displaced A. one cell to the end of the periodic system B . two cells to the beginning of the periodic system C. one cell to the beginning of the periodic system 4. Which of the following expressions corresponds to the law of radioactive decay. A.N=N02-t/T B. N=N0/2 C. N=N02-T 5. There are 109 atoms of the radioactive cesium isotope 55137Cs, its half-life is 26 years. Approximately how many isotope nuclei will remain undecayed after 52 years? A. 5108 B. 109 C. 2.5108 Answers 1 option 2 option 1A, 2A, 3B, 4C, 5C 1C, 2C, 3A, 4A, 5C VII. Summing up stage, information about homework. VIII. Reflection. Reflection of activities in the lesson Finish the phrase 1. today I learned ... 2. I was interested ... 3. I realized that ... 4. now I can ... 5. I learned ... 6. I have turned out... 7. surprised me... 8. gave me a lesson for life... 9. I felt like... Homework §§ 100,101.102, no. 1192, no. literature (if any) Myakishev G.Ya., Bukhovtsev B.B. Physics -11:. - M.:: Enlightenment, 2005 2. Koryakin Yu. I Biography of the atom. Moscow 1961 3. Encyclopedic Dictionary of a Young Physicist / comp. V.A. Chuyanov.: Pedagogy, 1984 4. Kasyanov V.A. Physics grade 11. - M.: Bustard, 2006. 5. Rymkevich A.P. Collection of problems in physics. - M.: Education, 2002. 6. Maron A.E., Maron E.A. Physics Grade 11: Didactic materials - M .: Bustard, 2004. Handout Test. "Radioactivity" Option 1 1. Which of the listed scientists called the phenomenon of spontaneous radiation radioactivity? A. The Curie spouses B. Rutherford S. Becquerel 2. -beams represent .... A. electron flow B. flow of helium nuclei C. electromagnetic waves 3. As a result of decay, the element shifts: A. one cell to the end of the system B. two cells to the beginning of the periodic system C. one cell to the beginning of the periodic system 4. The time during which half of the radioactive atoms decay is called ... A. decay time B. half-life C. decay period 5. There is 109 atoms of the radioactive isotope of iodine 53128I, its half-life is 25 min. Approximately what number of isotope nuclei will remain undecayed after 50 minutes? A. 5108 B. 109 C. 2.5108 Test. "Radioactivity" Option 2 1. Which of the following scientists is the discoverer of radioactivity? A. The Curies B. Rutherford S. Becquerel 2. - the rays represent ... A. the flow of electrons B. the flow of helium nuclei C. electromagnetic waves 3. As a result - the decay of the element is displaced A. one cell to the end of the periodic system B . two cells to the beginning of the periodic system C. one cell to the beginning of the periodic system 4. Which of the following expressions corresponds to the law of radioactive decay. A.N=N02-t/T B. N=N0/2 C. N=N02-T 5. There are 109 atoms of the radioactive cesium isotope 55137Cs, its half-life is 26 years. Approximately how many isotope nuclei will remain undecayed after 52 years? A. 5108 B. 109 C. 2.5108 Reflection of activities in the lesson Finish the sentence 1. today I learned ... 2. I was interested ... 3. I realized that ... 4. now I can ... 5. I learned... 6. I succeeded... 7. I was surprised... 8. gave me a lesson for life... 9. I wanted to...
About 2500 years ago, the ancient Greek philosophers Leucippus and Democritus suggested that all the bodies around us are made up of tiny particles invisible to the human eye. They called these particles atoms, which meant "indivisible." Thus emphasizing that the atom is the smallest of the particles that cannot be divided, and it has no constituent parts.
But by the middle of the 19th century, the theory of the indivisibility of atoms began to contradict some experimental facts. The idea began to emerge that atoms are not the smallest particles, but have a complex structure, and perhaps they include other electrically charged particles.
Discovery of the phenomenon
In 1896, a physicist from France, Henri Becquerel, discovered the phenomenon of radioactivity of atoms. He discovered that the chemical element uranium, without any external influences, that is, spontaneously, emits invisible rays unknown to science. Subsequently, these rays began to be called radioactive radiation. This was the most striking evidence of the fallacy of the theory of the indivisibility of atoms.
At that time, many scientists began to investigate radioactive radiation. It turned out that in addition to uranium, some other chemical elements also spontaneously emit radioactive rays.
- This property of the atoms of certain chemical elements is called radioactivity.
Detection of alpha, beta and gamma particles
Later, in 1899, the English physicist Rutherford discovered that the radioactive radiation of radium has a complex composition, that is, it is inhomogeneous. In order to establish this, the following experiment was carried out: a very thick-walled lead vessel was taken, and a grain of radium was placed in it. The vessel had a very narrow opening at the top. Through it, the radioactive rays of radium came out.
A photographic plate was placed above the vessel. After the photographic plate was developed, a dark spot was found on it exactly in the place where the beam of radioactive rays fell. Then the experience changed. A vessel with radium was placed in a strong magnetic field. After the development of the plate, there were three spots on it. One, as before, in the center, and the other two on opposite sides of it.
The deviation indicated that the radioactive rays, are streams of charged particles. And since there was a deviation in different directions, it means that some particles have different charges. Some particles were positively charged, some were negatively charged, and some (the central stream) had no charge at all.
Each of these particles got its own name. Positively charged particles became known as alpha particles, negatively charged particles as beta particles, and neutral particles as gamma particles.
- Spontaneous emission of radioactive radiation by a substance, served as the basis for the assumption that the atoms of substances have a complex composition and are not indivisible.
Alpha, beta and gamma radiation.
Lesson goals.
Educational - expansion of students' ideas about the physical picture of the world on the example of the phenomenon of radioactivity; study patterns
Educational – to continue the formation of skills: the theoretical method of studying physical processes; compare, generalize; to establish connections between the studied facts; put forward hypotheses and justify them.
educators – on the example of the life and work of Marie and Pierre Curie to show the role of scientists in the development of science; show the non-randomness of random discoveries; (thought: the responsibility of a scientist, a discoverer for the fruits of his discoveries), continue the formation of cognitive interests, collective skills, combined with independent work.
Didactic type of lesson: study and primary consolidation of new knowledge.
Lesson form: traditional
Necessary equipment and materials:
Sign of radioactive danger; portraits of scientists, computer, projector, presentation, workbook for students, periodic table of Mendeleev.
Methods:
information method (student messages)
problem
"There is nothing to be afraid of - you just need to understand the unknown"
Maria Sklodowska-Curie.
LESSON SUMMARY
Student motivation
To focus the attention of students on the material being studied, to interest them, to show the necessity and benefits of studying the material. Radiation - these are unusual rays, which are not visible to the eye and cannot be felt at all, but which can even penetrate walls and penetrate a person.
The course and content of the lesson
Lesson stages.
organizational stage.
The stage of preparation for the study of a new topic, motivation and updating of basic knowledge.
Stage of assimilation of new knowledge.
Stage of consolidation of new knowledge.
Summing up stage, information about homework.
Reflection.
.Organizing time
2. The stage of preparation for the study of a new topic
Actualization of the available knowledge of students in the form of checking homework and a cursory frontal survey of students.
I show the sign of radioactive danger and ask the question: “What does this sign mean? What is the danger of radioactive radiation?
3. Stage of assimilation of new knowledge (25 min)
Radioactivity appeared on the earth from the time of its formation, and man in the entire history of the development of his civilization was under the influence of natural sources of radiation. The Earth is exposed to the radiation background, the sources of which are solar radiation, cosmic radiation, radiation from radioactive elements lying in the Earth.
What is radiation? How does it arise? What types of radiation exist? And how to protect yourself from it?
The word "radiation" comes from the Latin radius and stands for beam. In principle, radiation is all types of radiation existing in nature - radio waves, visible light, ultraviolet, and so on. But radiations are different, some of them are useful, some are harmful. In ordinary life, we are accustomed to the word radiation to call harmful radiation arising from the radioactivity of certain types of matter. Let's analyze how the phenomenon of radioactivity is explained in physics lessons
Discovery of radioactivity by Henri Becquerel.
Perhaps only the memory of Antoine Becquerel would have remained as a highly qualified and conscientious experimenter, but no more, if not for what happened on March 1 in his laboratory.
The discovery of radioactivity was due to a happy accident. Becquerel studied the luminescence of substances previously irradiated with sunlight for a long time. He wrapped the photographic plate in thick black paper, placed grains of uranium salt on top, and exposed it to bright sunlight. After developing, the photographic plate turned black in those areas where the salt lay. Becquerel thought that the radiation of uranium arises under the influence of sunlight. But one day, in February 1896, he failed to conduct another experiment due to cloudy weather. Becquerel put the plate in a drawer, placing on top of it a copper cross covered with uranium salt. Having developed the plate, just in case, two days later, he found blackening on it in the form of a distinct shadow of a cross. This meant that uranium salts spontaneously, without any external influences, create some kind of radiation. Intensive research began. Soon, Becquerel established an important fact: the intensity of radiation is determined only by the amount of uranium in the preparation, and does not depend on which compounds it is included in. Therefore, radiation is inherent not in compounds, but in the chemical element uranium. Then a similar quality was discovered in thorium.
Becquerel Antoine Henri French physicist. He graduated from the Polytechnic School in Paris. The main works are devoted to radioactivity and optics. In 1896 he discovered the phenomenon of radioactivity. In 1901, he discovered the physiological effect of radioactive radiation. Becquerel was awarded the Nobel Prize in 1903 for his discovery of the natural radioactivity of uranium. (1903, together with P. Curie and M. Sklodowska-Curie).
Discovery of radium and polonium.
In 1898, other French scientists Marie Sklodowska-Curie and Pierre Curie isolated two new substances from the uranium mineral, much more radioactive than uranium and thorium. So two previously unknown radioactive elements were discovered - polonium and radium. It was exhausting work, for four long years the couple almost did not leave their damp and cold barn. Polonium (Po-84) was named after Mary's homeland, Poland. Radium (Ra-88) - radiant, the term radioactivity was proposed by Maria Sklodowska. All elements with serial numbers greater than 83 are radioactive, i.e. located in the periodic table after bismuth. For 10 years of joint work, they have done a lot to study the phenomenon of radioactivity. It was a selfless work in the name of science - in a poorly equipped laboratory and in the absence of the necessary funds Researchers received the preparation of radium in 1902 in the amount of 0.1 g. To do this, they took 45 months of hard work there and more than 10,000 chemical liberation and crystallization operations.
No wonder Mayakovsky compared poetry with the extraction of radium:
“Poetry is the same extraction of radium. A gram of production, a year of labor. Exhausting a single word for the sake of a thousand tons of verbal ore.
In 1903, the Curies and A. Becquerel were awarded the Nobel Prize in Physics for their discovery in the field of radioactivity.
RADIOACTIVITY -
is the ability of some atomic nuclei to spontaneously transform into other nuclei, while emitting various particles:
All spontaneous radioactive decay is exothermic, that is, it releases heat.
Student message
Maria Sklodowska-Curie - Polish and French physicist and chemist, one of the founders of the theory of radioactivity was born on November 7, 1867 in Warsaw. She is the first woman professor at the University of Paris. For research on the phenomenon of radioactivity in 1903, together with A. Becquerel, she received the Nobel Prize in Physics, and in 1911 for obtaining radium in the metallic state - the Nobel Prize in Chemistry. Died of leukemia July 4, 1934. The body of Marie Sklodowska-Curie, enclosed in a lead coffin, still emits radioactivity with an intensity of 360 becquerel/M3 at a rate of about 13 bq/M3... She was buried with her husband...
Student message
- Pierre Curie - French physicist, one of the creators of the theory of radioactivity. Opened (1880) and investigated piezoelectricity. Studies on crystal symmetry (Curie principle), magnetism (Curie law, Curie point). Together with his wife, M. Sklodowska-Curie, he discovered (1898) polonium and radium and studied radioactive radiation. Introduced the term "radioactivity". Nobel Prize (1903, jointly with Sklodowska-Curie and A. A. Becquerel).
The complex composition of radioactive radiation
In 1899, under the guidance of the English scientist E. Rutherford, an experiment was carried out that made it possible to detect the complex composition of radioactive radiation.
As a result of an experiment conducted under the guidance of an English physicist , the radioactive emission from radium was found to be inhomogeneous, i.e. it has a complex structure.
Rutherford Ernst (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). Director of the Cavendish Laboratory (since 1919). Opened (1899) alpha and beta rays and established their nature. Created (1903, together with F. Soddy) the theory of radioactivity. He proposed (1911) a planetary model of the atom. Carried out (1919) the first artificial nuclear reaction. Predicted (1921) the existence of the neutron. Nobel Prize (1908).
A classic experiment that made it possible to detect the complex composition of radioactive radiation. 
The radium preparation was placed in a lead container with a hole. A photographic plate was placed opposite the hole. A strong magnetic field acted on the radiation.
Almost 90% of known nuclei are unstable. Radioactive nuclei can emit particles of three types: positively charged (α-particles - helium nuclei), negatively charged (β-particles - electrons) and neutral (γ-particles - quanta of short-wave electromagnetic radiation). The magnetic field allows these particles to be separated.
4) Penetration α .β. γ radiation
α-rays have the least penetrating power. A layer of paper 0.1 mm thick is no longer transparent for them. 
. β-rays are completely blocked by an aluminum plate several mm thick.
γ-rays, when passing through a 1 cm layer of lead, reduce the intensity by 2 times.
5) Physical nature of α .β. γ radiation
γ-radiation electromagnetic waves 10 -10 -10 -13 m
Gamma radiation is photons, i.e. electromagnetic wave that carries energy. In the air, it can travel long distances, gradually losing energy as a result of collisions with the atoms of the medium. Intense gamma radiation, if not protected from it, can damage not only the skin, but also internal tissues. Dense and heavy materials such as iron and lead are excellent barriers to gamma radiation.
S. Becquerel
2.-rays are….
A. electron flow
3. As a result of -decay, the element is displaced
Option 2
1. Which of the scientists listed below is the discoverer of radioactivity?
A. The Curies
W. Rutherford
S. Becquerel
2. -rays are ...
A. electron flow
V. flow of helium nuclei
C. electromagnetic waves
3. As a result of -decay, the element is displaced
A. one cell to the end of the periodic table
B. two cells to the beginning of the periodic system
C. one cell to the beginning of the periodic system
5. Stage of debriefing, information about homework.
6. Reflection of activities in the lesson
Finish the phrase
today I found out...
it was interesting to me…
I realized that...
Now I can…
I learned…
I managed …
surprised me...
gave me a lesson for life...
I wanted…
Maria Sklodowska-Curie.
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99,100
REVIEW
for the methodological development of a lesson in the discipline Physics
Surname, name, patronymic of the author - Shepeleva Raisa Alexandrovna
Position - teacher of general education disciplines
Name of methodical development: Discovery of radioactivity. Alpha beta and gamma radiation
Full name of the educational institution OGAOU SPO "Rakityan Agrotechnological College"
Educational institution address settlement Rakitnoye, Belgorodskaya region, st. Kommunarov, 11
At the control and evaluation stage, it is proposed to conduct a test control. The material of the tasks is aimed not only at testing knowledge and skills, but also contributes to further use in the course of studying the topic.
The main forms of organization of educational activities are frontal, group and individual forms of work. The active inclusion of children in the educational process occurs due to a properly planned process of goal-setting and posing a problematic issue.
Basic teaching methods: explanatory and illustrative, reproductive, partially exploratory. The selected teaching aids contribute to a better perception and assimilation of the material.
Primary consolidation of the material is carried out in the form of verification workorganized into groups.
The use of a PC allows not only to enhance the visual representation of the material being studied, but also contributes to its more meaningful assimilation. The slide presentation contains all the necessary visual and practical material. All this allows you to increase the density of the lesson and optimally increase its pace. The reflexive-evaluative stage was held in the form of a polylogue, to determine the degree of students' difficulties in studying the topic, as well as planning long-term individual goals.
Surname, name, patronymic of the reviewer (in full) ___________________
Position ___________________________________________________
Place of work _________________________________________________
Discoveries at the end of the 19th century and the first five years of the 20th century. led to a revolution in the physical worldview. The idea of immutable atoms, of mass as a constant amount of matter, of Newton's laws as unshakable foundations of the physical picture of the world, of absolute space and time, collapsed, discreteness and discontinuity were discovered in continuous processes.
The idea of immutable, indestructible atoms, which existed in physics and philosophy since the time of Democritus, was destroyed by the discovery of radioactivity. Already at the very beginning of research on radioactivity, Maria Sklodowska-Curie wrote: “The radioactivity of uranium and thorium compounds seems to be atomic, properties ... I studied uranium and thorium compounds from this point of view and made many measurements of their activity under various conditions. It follows from the totality of these measurements that the radioactivity of these compounds is indeed an atomic property. It appears here connected with the presence of atoms of both elements under consideration and is not destroyed either by a change in the physical state or by chemical transformations.
Thus, it turned out that the atoms of uranium, thorium, and later discovered polonium and radium are not dead bricks, but have activity, emit rays. The nature of these rays was investigated by a number of scientists, but Rutherford was the first to discover the complex composition of radioactive rays. In an article published in 1899, "The radiation of uranium and the electrical conductivity caused by it," he showed by the electrical method that the radiation of uranium has a complex composition.
One of the capacitor plates was covered with uranium salt powder and connected to the battery pole, the second was connected to the quadrant of a quadrant electrometer, the other pair of quadrants of which was connected to the grounded battery pole. The rate of discharge caused by the ionizing action of uranium rays was measured. The powder was covered with thin sheets of metal foil. “These experiments,” wrote Rutherford, “show that the radiation of uranium is inhomogeneous in composition—at least two different types of radiation are present in it. One is very strongly absorbed, let's call it α-radiation for convenience, and the other has a large penetrating power, let's call it P-radiation.
During the research, Rutherford learned about the work of Schmidt, who discovered the radioactivity of thorium (he apparently did not know about the similar discovery of Sklodowska-Curie). He investigated the radiation of thorium and found that the a-radiation of thorium has a greater penetrating power than the a-radiation of uranium. He also stated that the radiation of thorium "is inhomogeneous in composition, it contains some rays of great penetrating power." However, Rutherford did not conduct an accurate analysis of thorium radiation. In 1900 Vilar discovered strongly penetrating weak radiation. Vilar's rays became known as 7-rays.
It turned out that α -, β -, γ - rays differ not only in their penetrating power. Becquerel in 1900 showed that p-rays are deflected by a magnetic field in the same direction as cathode rays. This result was obtained by the Curies, Meyer, Schweidler and others. These experiments showed, as Rutherford wrote in 1902, that "the deflected rays are in all respects similar to cathode rays." Rutherford directly speaks of β-rays as electrons. Carrying out experiments with β-rays, V. Kaufman in 1901 discovered the dependence of the mass on the speed.
In February 1903, Rutherford showed that "non-deflectable" a-rays are in fact "deflected in strong magnetic and electric fields. These rays are deflected in the opposite direction compared to the cathode rays and, therefore, must consist of positively charged particles moving at high speed.
In 1903, in her doctoral dissertation "Research on Radioactive Substances", M. Sklodowska-Curie gave a diagram of the structure of radioactive radiation according to their deflection in a magnetic field, which has since been included in all textbooks.
Shortly after the discovery of polonium and radium, the Curies established "that the rays emitted by these substances, acting on inactive substances, are capable of imparting radioactivity to them and that this induced radioactivity persists for a sufficiently long time."
Then Rutherford, studying the radioactivity of thorium compounds, wrote that these compounds, in addition to ordinary radioactive rays, "continuously emit some kind of radioactive particles that retain radioactive properties for several minutes." Rutherford called these particles "emanation". “In its photographic and electrical effects, the emanation is similar to uranium. It is capable of ionizing the surrounding gas and acts in the dark on a photographic plate with an exposure of several days. Rutherford, in experiments with thorium compounds, confirmed their property to excite "in any solid substance located next to it, radioactivity, which disappears with time," that is, the induced radioactivity that Curie had observed a year before. He further showed that there is a close connection between the emanation of thorium and excited radioactivity. "Emanation," Rutherford wrote, "is in a sense the immediate cause of the excitation of radioactivity." Rutherford did not detect the emission of emanation from a sample of "not quite pure radium" in his possession. However, Dorn later used a purer sample of radium and showed that radium had the same emanation power as thorium.
“According to Rutherford,” Sklodowska-Curie wrote in her dissertation, “the emanation of a radioactive body is a material, radioactive gas released from this body.” In 1902, Rutherford and Soddy published the first article, The Cause and Nature of Radioactivity. Investigating the ability of thorium compounds to emit emanation, they chemically isolated an active component from thorium hydroxide, "having specific chemical properties and activity at least 1000 times greater than the activity of the substance from which it was isolated."
Referring to the example of Crookes, who in 1900 isolated the active component from uranium, which Crookes called UX, Rutherford and Soddy named the component they isolated from thorium ThX. As a result of careful research, they came to the conclusion: “The radioactivity of thorium at any moment is the radioactivity of two opposite processes:
1) the formation of a new active substance at a constant rate by the thorium compound;
2) decrease over time in the emissivity of the active substance.
The normal or permanent radioactivity of thorium is an equilibrium state in which the rate of increase in radioactivity due to the formation of a new active substance is balanced by the rate of decrease in the radioactivity of an already formed substance.
This leads to the cardinal conclusion that Rutherford and Soddy formulate as follows: "...radioactivity is an atomic phenomenon, simultaneously accompanied by chemical changes, as a result of which new types of matter appear, and these changes must take place inside the atom, and radioactive elements must undergo spontaneous transformations" .
Rutherford and Soddy's first article appeared in the September issue of the Philosophical Magazine. The second article appeared in the November issue. Describing the experiment to measure the emanation power, Rutherford and Soddy wrote further: “Sufficient data have been given to show clearly that in both the radioactivity of thorium and radium, the most complex transformations are manifested, each of which is accompanied by the continuous formation of a special kind of active substance.” The emanation formed from radium and thorium is an inert gas. Scientists are paying attention to the connection of radioactivity with helium, which is possibly the end product of decay.
In April and May 1903, new works by Rutherford and Soddy appeared - "A Comparative Study of the Radioactivity of Radium and Thorium" and "Radioactive Transformation". Now they already state with all certainty that “all the cases of radioactive transformation studied are reduced to the formation of one substance from another (if the emitted rays are not taken into account). When several transformations occur, they do not occur simultaneously, but sequentially.
Further, Rutherford and Soddy formulate the law of radioactive transformation: “In all cases when one of the radioactive products was separated and its activity was examined, regardless of the radioactivity of the substance from which it was formed, it was found that the activity in all studies decreases with time according to the law of geometric progression” .
It follows that "the rate of transformation is always proportional to the number of systems that have not yet undergone transformation":
In other words: "The relative amount of radioactive material that turns into a unit of time is a constant value." This constant was called the radioactive constant by Rutherford and Soddy, and is now called the decay constant.
From their discovery, Rutherford and Soddy draw important conclusions about the existence of new radioactive elements that can be identified by their radioactivity, even if they are present in negligible amounts.
The prediction of Rutherford and Soddy brilliantly came true, and the methods of radiochemistry created by the Curies, Rutherford and Soddy, became a powerful tool in the discovery of new elements, which made it possible to identify the new, 101st element, Mendeleevium - in the amount of only 17 atoms.
In their classic work, Rutherford and Soddy touched on the fundamental question of the energy of radioactive transformations. Calculating the energy of a-particles emitted by radium, they come to the conclusion that "the energy of radioactive transformations is at least 20,000 times, and maybe even a million times greater than the energy of any molecular transformation." Moreover, these energy estimates concern only the radiation energy, and not the total energy of radioactive transformation, which, in turn, can be only a part of the internal energy of the atom, since the internal energy of the resulting products remains unknown.
Rutherford and Soddy believe that "the energy hidden in the atom is many times greater than the energy released in ordinary chemical transformation." This huge energy, in their opinion, should be taken into account "when explaining the phenomena of space physics." In particular, the constancy of solar energy can be explained by the fact that the processes of subatomic transformation are taking place on the Sun.
Once again one is astonished at the foresight of the authors, who as early as 1903 saw the cosmic role of nuclear energy. 1903 was the year of the discovery of this new form of energy, about which Rutherford and Soddy spoke with such definiteness, calling it intra-atomic energy.
In the same year, in Paris, Pierre Curie and his collaborator Laborde measured the heat spontaneously released by radium salts. He established: "1 gram of radium releases an amount of heat on the order of 100 small calories in one hour." “The continuous release of such an amount of heat,” wrote Curie, “cannot be explained by ordinary chemical transformation. If we look for the reason for the formation of heat in some internal transformations, then these transformations must be of a more complex nature and must be caused by some changes in the radium atom itself.
True, Curie admitted the possibility of some other mechanism of energy release. Marie Skłodowska-Curie suggested that radioactive elements take their energy from outer space. It is “constantly permeated with some still unknown radiations, which, upon meeting with radioactive bodies, are delayed and converted into radioactive energy.” But this hypothesis, expressed by her in 1900, remarkable for the idea of cosmic radiation contained in it, was abandoned, and in 1903 Curie admitted: "Recent research favors the hypothesis of atomic transformations of radium."
1903 should be considered a red date in the history of radioactivity. This is the year of the discovery of the law of radioactive transformations and a new type of energy - atomic energy, which manifests itself in these transformations. This is the year of birth of the first device that allows you to "see" individual atoms - the Crookes spinthariscope. “The essential part of this device,” wrote Maria Sklodowska-Curie, “is a grain of radium salt, fixed at the end of a metal wire in front of a screen of phosphorescent zinc. The distance from the radium to the screen is very small (about 1/2 mm). The side of the screen facing the radium is observed through a magnifying glass. The eye sees here a veritable rain of luminous dots, constantly flashing and disappearing again; The screen looks like a starry sky.
Having expressed the hypothesis that each flash of the screen is due to the impact of an a-particle on it, Curie writes that in this case "here for the first time we would have before us a phenomenon that makes it possible to distinguish the individual action of a particle having atomic dimensions." And so it turned out.
Finally, on June 25, 1903, Marie Sklodowska-Curie defends her doctoral dissertation, from which we have taken the description of the spinthariscope, and becomes the first woman in France to receive this high scientific degree. Here we have entered the realm of personal biographies and, since this has happened, we will give a brief biographical note about one of the authors of the law of radioactive decay - Frederick Soddy.
Frederick Soddy was born on September 2, 1877. In 1896 he graduated from Oxford University. His name entered the history of science from the time he worked with Rutherford in Montreal, Canada in 1900-1902, and came with him to the theory of radioactive transformations. In 1903-1904. Soddy worked with W. Ramsay at the University of London, and here in 1903, together with Ramsay, he proved by spectroscopic means that helium is obtained from the emanation of radium. From 1904 to 1914 Soddy was a professor at the University of Glasgow. Here, independently of earthenware, he discovers the law of radioactive displacement (1913) and introduces the concept of isotopes.
From 1914 to 1919 Soddy was a professor at the University of Aberdeen, from 1919 to 1936 he was a professor at Oxford University. In 1921 Soddy received the Nobel Prize in Chemistry.
He is the author of a number of books on radioactivity and radiochemistry, some of which have been translated into Russian: Radium and Its Solution, Matter and Energy, Chemistry of Radioelements, Radium and the Structure of the Atom.
Soddy was one of the earliest adopters of atomic energy. In the book "Radium and Its Solution", a Russian translation of which was published in 1910, he raises the question: do non-radioactive elements have an energy reserve? He solves it in the sense that "this internal reserve of energy, which we first met in connection with radium, is possessed to a greater or lesser extent by all the elements in general and that it is an integral feature of their internal structure." During the transmutation (transformation) of elements, energy is released.
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