What are Rutherford's scientific discoveries about the atom. Rutherford Ernest: biography, experiences, discoveries
What Rutherford surpassed Einstein and what Marconi was inferior to, what mega-grants there were in England in the 19th century, what losses the great scientist suffered in the First World War and why he was called the Crocodile and the Rabbit, the site tells in the next issue of the “How to Get a Nobel Prize” section.
Monument to Rutherford the Child in New Zealand
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Ernest Rutherford
Nobel Prize in Chemistry 1908. The formulation of the Nobel Committee: “For his research in the field of decay of elements in the chemistry of radioactive substances.”
When writing an article about a Nobel laureate, there are two particularly difficult situations. The first option: very little is known about our hero, and we have to do a separate search to gather material for the article. The second option: our hero is super famous, his name has become a household name, and the memories of eyewitnesses often contradict each other. And here another question arises - the question of choice. Our case today is exactly that. There are very few laureates who are as famous as our character. Even fewer have received the Nobel Prize, so much so that the nomination itself in his case became the most striking case of trolling in the history of science. Although back in 1908, only a musical scene by Edvard Grieg could be called “trolling.” But what else can you call a prize in chemistry awarded to a physicist to the core, who himself has repeatedly emphasized that all sciences “are divided into physics and stamp collecting”? On the other hand, the name of this person in different times three chemical elements were named. Have you already guessed who our hero is? Of course, it's him, New Zealand's first Nobel laureate, Sir Ernest Rutherford. He is with light hand the future Soviet Nobel laureate and his student Pyotr Kapitsa - Crocodile.
Young Ernest Rutherford
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Rutherford can be considered lucky. Having been born further away than in the provinces, not in some Devonshire, not in Edinburgh, not in Sydney or even in Wellington, but in the New Zealand province, in a farming family, he managed to make his way. However, our hero received a scholarship named after the 1851 World Exhibition for gifted provincials only when the one who had been awarded it earlier refused.
Nevertheless, the Rubicon was crossed (as he wrote to his bride), the money for the ship was borrowed, and with a prototype of a radio wave detector (Marconi and Popov did about the same thing), Rutherford set off for England. He was not given any money to develop the detector: the British Post Office put all its funds on Marconi, who would receive the Nobel Prize a year after Rutherford. And the New Zealander enrolled in the Cavendish Laboratory at Cambridge.
Few people know that the famous Cavendish Laboratory is named after not the chemist Henry Cavendish (who was the 2nd Duke of Devonshire), but his relative, the 7th Duke of Devonshire, William Cavendish, Chancellor of Cambridge, who donated money to open the laboratory. This is the English mega-grant. By the way, very successful: to date, 29 employees of this project have received Nobel Prizes(including our Kapitsa).
William Cavendish, 7th Duke of Devonshire
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Rutherford became a doctoral student with the discoverer of the electron himself (Thomson was the laureate of the “Nobel in Physics” in 1906, but not for the electron, but for his studies of the passage of currents in gases). And took part in his Nobel works scientific supervisor. And then we can simply list only the main achievements of Rutherford, a great experimenter and physicist (Dr. Andrew Balfour gave a caustic definition and recognition of Rutherford: “We got a wild rabbit from the country of the antipodes and he digs deep”).
Together with Thomson he studied the ionization of gases x-ray radiation. In 1898, he isolated “alpha rays” and “beta rays” from radioactive radiation. Now we know that these are helium nuclei and electrons. By the way, chemical nature Rutherford's Nobel lecture was devoted to alpha rays.
Experimental installation for separating radioactive radiation into alpha, beta and gamma components
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In 1901-1903, together with the future Nobel laureate in chemistry in 1921, Frederick Soddy, Rutherford discovered the natural transformations of elements during radioactive decay (for this our hero received the Nobel, so everything is legal, because chemistry is the science of the transformation of substances) to a friend). At the same time, the “emanation of thorium”, gaseous radon-220, was discovered, and the law of radioactive decay was formulated.
Frederick Soddy
Hans Geiger and Ernest Rutherford
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But he (more precisely, his students Geiger and Mardsen) conducted his most famous experiment in 1909. A study of the passage of alpha particles through gold foil, completely unexpectedly, showed that some helium nuclei are thrown back. “It is as if you were shooting a 15-inch shell at a piece of tissue paper and the shell came back and struck you,” Rutherford wrote. Thus, the atomic nucleus was discovered and the planetary model of the atom appeared, in which electrons revolve around the nucleus, and Thomson's model, which was called “raisin pudding,” was discarded.
How would alpha particles pass through Thomson's atoms (the expected result of the experiment) and what results were observed in reality
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To propose such a model was complete madness. Then it turned out that, for example, Einstein thought about the planetary model of the atom, but did not dare to develop it, because it is clear to everyone that sooner or later electrons must fall onto the nucleus.
During World War I, Rutherford worked on detecting enemy submarines (he served as a communications officer). The war dealt our hero a terrible blow: his most talented student, Henry Moseley, died at the front.
Henry Moseley
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In 1917, Rutherford began experiments on the artificial transformation of elements. Two years later, these experiments were successfully completed: in 1919, in the same Philosophical Magazine, where he and Soddy talked about the transformation of elements during natural radioactive decay, the article “An Anomalous Effect in Nitrogen” was published, which reported the first artificial transformation of elements). In 1920, Rutherford predicted the existence of the neutron (it was later discovered by Rutherford's student Chadwick).
Sir James Chadwick
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During the war, Rutherford also became a nobleman. Despite the fact that Rutherford received a blow from the king in 1914, he officially became Baron Rutherford Nelson only in 1931, with the approval of the corresponding coat of arms. The coat of arms features the kiwi bird, the symbol of New Zealand, and two exponential curves showing how the quantity decreases over time radioactive atoms during radioactive decay. He telegraphed via submarine cable to his eighty-eight-year-old mother: “So - Lord Rutherford. The credit is more yours than mine. Love, Ernest."
Ernest Rutherford born August 30, 1871 in Brightwater, a picturesque place in New Zealand. He was the fourth child in the family of Scottish immigrants James Rutherford and Martha Thomson, and of the twelve children he turned out to be the most gifted. Ernest finished brilliantly primary school, receiving 580 points out of 600 possible and a bonus of 50 pounds sterling for further education.
At Nelson College, where Ernest Rutherford was accepted into the fifth form, teachers noticed his exceptional mathematical abilities. But Ernest did not become a mathematician. He did not become a humanitarian, although he showed remarkable abilities in languages and literature. Fate would have decreed that Ernest would become carried away natural sciences- physics and chemistry.
After graduating from college, Rutherford entered the University of Canterbury, and already in his second year he gave a report on “The Evolution of the Elements,” in which he suggested that chemical elements represent complex systems, consisting of the same elementary particles. Ernest's student report was not properly assessed at the university, but his experimental work, for example, the creation of a receiver electromagnetic waves, surprised even major scientists. Just a few months later he was awarded the "1851 Scholarship", which recognized the most talented graduates of provincial English universities.
After this, Rutherford three years worked in Cambridge, at the Cavendish Laboratory, under the guidance of the famous physicist Joseph-John Thomson. In 1898 he began studying radioactivity. Rutherford's first fundamental discovery in this area - the discovery of the inhomogeneity of radiation emitted by uranium - made his name famous in scientific world; Thanks to him, the concept of alpha and beta radiation entered science.
That same year, 26-year-old Rutherford was invited to Montreal as a professor at McGill University, the best in Canada. This university was named after its founder - an immigrant from Scotland, who at the end of his life managed to get rich. Before Rutherford left for Canada, J. Thomson handed him a letter of recommendation, which was written: “In my laboratory there has never been a young scientist with such enthusiasm and ability for original research as Mr. Rutherford, and I am confident that if he is elected , will create an outstanding school of physicists in Montreal..." Thomson's prediction came true. Rutherford worked in Canada for 10 years and actually created a scientific school there.
In 1903, the 32-year-old scientist was elected a member of the Royal Society of London - the British Academy of Sciences.
In 1907, Rutherford and his family moved from Canada to England to take up the position of professor in the department of physics at the University of Manchester. Immediately after his arrival, Rutherford began experimental studies of radioactivity. Working with him was his assistant and student, the German physicist Hans Geiger (1882-1945), who developed an ionization method for measuring radiation intensity - the well-known Geiger counter. Rutherford carried out a series of experiments that confirmed that alpha particles are doubly ionized helium atoms. Together with his other student, Ernest Marsden (1889-1970), he studied the peculiarities of the passage of alpha particles through thin metal plates. Based on these experiments, the scientist proposed a planetary model of the atom: in the center of the atom there is a nucleus around which electrons rotate. Rutherford predicted the discovery of the neutron, the possibility of fission atomic nuclei light elements and artificial nuclear transformations.
For 18 years - from 1919 until the end of his life - Rutherford headed the Cavendish Laboratory, founded in 1874. Before him, it was led by the great English physicists Maxwell, Rayleigh and Thomson. Rutherford lived only a few years before the German physicists Otto Hahn (1879-1968) and Lise Meitner (1878-1968) discovered the fission of uranium.
According to Patrick Blackett, one of Rutherford's closest collaborators, this discovery " in a sense, was the last of the great discoveries in nuclear physics, which differs from particle physics. Rutherford did not live to see the culmination of the development of the direction that was actually the area of his scientific activity".
The first page of E. Rutherford's article in the Philosophical Magazine, 6, 21 (1911), in which the concept of “atomic nucleus” was first introduced.
The atomic nucleus, discovered 100 years ago by E. Rutherford, is a bound system of interacting protons and neutrons. Each atomic nucleus is unique in its own way. To describe atomic nuclei, various models have been developed that describe individual specific features of atomic nuclei. The study of the properties of atomic nuclei discovered new world- the subatomic quantum world, led to the establishment of new laws of conservation and symmetry. The knowledge obtained in nuclear physics is widely used in natural sciences from the study of living systems to astrophysics.
1. 1911 Rutherford discovers the atomic nucleus.
In the June 1911 issue of the Philosophical Magazine, E. Rutherford’s work “Scattering of α- and β-particles by matter and the structure of the atom” was published, in which the concept of "atomic nucleus".
E. Rutherford analyzed the results of the work of G. Geiger and E. Marsden on the scattering of α-particles on thin gold foil, in which it was unexpectedly discovered that a small number of α-particles were deflected by an angle greater than 90°. This result contradicted the then dominant model of the atom by J. J. Thomson, according to which the atom consisted of negatively charged electrons and an equal amount of positive electricity uniformly distributed within a sphere of radius R ≈ 10 - 8 cm. To explain the results obtained by Geiger and Marsden, Rutherford developed a model for the scattering of a point electric charge by another point charge based on Coulomb’s law and Newton’s laws of motion and obtained the dependence of the probability of α-particle scattering at an angle θ on the energy E of the incident α-particle
The angular distribution of α particles measured by Geiger and Marsden could only be explained if we assumed that the atom had a central charge distributed over a region the size<10 -12 см. Результирующий заряд ядра приблизительно равен Ae/2, где A - вес атома в атомных единицах массы, e - фундаментальная единица заряда. Точность определения величины заряда ядра золота составила ≈ 20%. Так возникла планетарная модель атома, согласно которой атом состоит из массивного положительно заряженного атомного ядра и вращающихся вокруг него электронов. Так как в целом атом электрически нейтрален - положительный заряд ядра компенсировался отрицательным зарядом электронов. Число электронов в атоме определялось величиной заряда ядра Z.
In 1910, a young scientist named Marsden came to work in Rutherford's laboratory. He asked Rutherford to give him some very simple problem. Rutherford instructed him to count alpha particles passing through matter and find their scattering. At the same time, Rutherford noted that, in his opinion, Marsden would not find anything noticeable. Rutherford based his considerations on the Thomson model of the atom accepted at that time. In accordance with this model, the atom was represented by a sphere measuring 10 -8
cm with an equally distributed positive charge, in which electrons were interspersed. The harmonic vibrations of the latter determined the emission spectra. It is easy to show that alpha particles should easily pass through such a sphere, and special scattering could not be expected. The alpha particles spent all the energy along their path to eject electrons, which ionized the surrounding atoms.
Marsden, under the guidance of Geiger, began to make his observations and soon noticed that most α particles pass through matter, but there is still noticeable scattering, and some particles seem to bounce back. When Rutherford found out about this, he said:
— This is impossible. This is as impossible as it is impossible for a bullet to bounce off paper.
This phrase shows how concretely and figuratively he saw the phenomenon.
Marsden and Geiger published their work, and Rutherford immediately decided that the existing idea of the atom was incorrect and needed to be radically revised.
By studying the law of distribution of reflected α-particles, Rutherford tried to determine what field distribution inside the atom was necessary in order to determine the law of dispersion under which α-particles could even return back. He came to the conclusion that this is possible when the entire charge is concentrated not throughout the entire volume of the atom, but in the center. The size of this center, which he called the nucleus, is very small: 10 -12
—10
-13
cm in diameter. But where then should we place the electrons? Rutherford decided that the negatively charged electrons should be distributed in a circle - they could be held by rotation, the centrifugal force of which balances the attractive force of the positive charge of the nucleus. Consequently, the model of the atom is nothing more than a certain solar system, consisting of a core - the sun and electrons - the planets. So he created his model of the atom.
This model met with complete bewilderment, since it contradicted some of the then, seemingly unshakable, fundamentals of physics..
P.L. Kapitsa. "Memories of Professor E. Rutherford"
1909-1911 Experiments by G. Geiger and E. Marsden
G. Geiger and E. Marsden saw that when passing through a thin gold foil, most α particles, as expected, flew through without deflection, but unexpectedly it was discovered that some α particles were deflected at very large angles. Some alpha particles were even scattered in the opposite direction. Calculations of the electric field strength of atoms in the Thomson and Rutherford models show a significant difference between these models. The field strength of a positive charge distributed over the surface of an atom in the case of the Thomson model is ~10 13 V/m. In Rutherford's model, the positive charge located at the center of the atom in the region R< 10 -12 см создаёт напряженности поля на 8 порядков больше. Только такое сильное электрического поле массивного заряженного тела может отклонить α-частицы на большие углы, в то время как в слабом электрическом поле модели Томсона это было невозможно.
E. Rutherford, 1911 "It is well known thatα - Andβ -particles, when colliding with atoms of a substance, experience deviation from a straight path. This scattering is much more noticeable inβ -particles thanα -particles, because they have significantly lower impulses and energies. There is therefore no doubt that such rapidly moving particles penetrate the atoms they encounter and that the observed deviations are due to the strong electric field acting within the atomic system. It was usually assumed that beam scatteringα - orβ -rays passing through a thin plate of matter are the result of numerous small scatterings during the passage of atoms of the substance. However, observations made by Geiger and Marsden showed that a certain amountα -particles in a single collision experience a deflection of more than 90°. A simple calculation shows that a strong electric field must exist in the atom for such a large deflection to be created during a single collision.”
1911 E. Rutherford. Atomic nucleus
| α + 197 Au → α + 197 Au |
 Ernest Rutherford (1891-1937) |
Based on the planetary model of the atom, Rutherford derived a formula describing the scattering of α particles on a thin gold foil, consistent with the results of Geiger and Marsden. Rutherford assumed that α particles and the atomic nuclei with which they interact can be considered as point masses and charges and that only electrostatic repulsive forces act between positively charged nuclei and α particles and that the nucleus is so heavy compared to the α particle that it does not move during interaction. Electrons rotate around the atomic nucleus on a characteristic atomic scale of ~10-8 cm and, due to their low mass, do not affect the scattering of α-particles.
First, Rutherford obtained the dependence of the scattering angle θ of an α-particle with energy E on the impact parameter b of a collision with a point massive nucleus. b - impact parameter - the minimum distance at which the α-particle would approach the nucleus if there were no repulsive forces between them, θ - scattering angle of the α-particle, Z 1 e - electric charge of the α-particle, Z 2 e - electric charge kernels.
Rutherford then calculated what fraction of a beam of α particles with energy E is scattered by an angle θ depending on the charge of the nucleus Z 2 e and the charge of the α particle Z 1 e. Thus, based on the classical laws of Newton and Coulomb, the famous Rutherford scattering formula was obtained. The main thing in deriving the formula was the assumption that the atom contains a massive positively charged center, the dimensions of which are R< 10 -12
см.
E. Rutherford, 1911: “The simplest assumption is that the atom has a central charge distributed over a very small volume, and that large single deviations are due to the central charge as a whole, and not to its constituent parts. At the same time, the experimental data are not accurate enough to deny the possibility of the existence of a small part of the positive charge in the form of satellites located at some distance from the center... It should be noted that the found approximate value of the central charge of the gold atom (100e) approximately coincides with the value found which would have a gold atom consisting of 49 helium atoms each carrying a charge of 2e. Perhaps this is just a coincidence, but it is very tempting from the point of view of the emission of helium atoms carrying two units of charge by a radioactive substance.”
J. J. Thomson and E. Rutherford
E. Rutherford, 1921:“The concept of the nuclear structure of the atom originally arose from attempts to explain the scattering of α particles at large angles when passing through thin layers of matter. Since α particles have large mass and high speed, these significant deviations were extremely remarkable; they indicated the existence of very electrically intense ones! or magnetic fields inside atoms. To explain these results, it was necessary to assume that the atom consists of a charged massive nucleus, very small in size compared to the usually accepted value of the diameter of the atom. This positively charged nucleus contains most of the mass of the atom and is surrounded at some distance by negative electrons distributed in a certain manner; the number of which is equal to the total positive charge of the nucleus. Under such conditions, a very intense electric field should exist near the nucleus and α-particles, when meeting an individual atom, passing close to the nucleus, are deflected at significant angles. Assuming that the electric forces vary inversely with the square of the distance in the region adjacent to the nucleus, the author obtained a relation relating the number of α-particles scattered at a certain angle with the charge of the nucleus and the energy of the α-particle.
The question whether the atomic number of an element is a valid measure of its nuclear charge is so important that every possible method must be applied to resolve it. Several studies are currently underway at the Cavendish Laboratory to test the accuracy of this relationship. The two most direct methods are based on studying the scattering of fast α- and β-rays. The first method is used by Chadwick, who uses new techniques; the last is by Crowthar. The results obtained so far by Chadwick fully confirm the identity of the atomic number with the nuclear charge within the limits of the possible accuracy of the experiment, which for Chadwick is about 1%.”
Despite the fact that the combination of two protons and two neutrons is an extremely stable formation, it is currently believed that α particles are not included in the nucleus as an independent structural formation. In the case of α-radioactive elements, the binding energy of the α particle is greater than the energy required to separately remove two protons and two neutrons from the nucleus, so the α particle can be emitted from the nucleus although it is not present in the nucleus as independent education.
Rutherford's assumption that the atomic nucleus may consist of a certain number of helium atoms or about positively charged satellites of the nucleus was a completely natural explanation for his discovery α
radioactivity. The idea that particles could be created as a result of various interactions did not yet exist at that time.
The discovery of the atomic nucleus by E. Rutherford in 1911 and the subsequent study of nuclear phenomena radically changed our understanding of the world around us. It enriched science with new concepts and was the beginning of the study of the subatomic structure of matter.
One of the most famous physicists, Ernest Resenford, was from New Zealand. His family was not rich, and Resenford himself was the fourth child of twelve. It would seem that he does not have any special future, but on the contrary, since childhood, the scientist has strived for education, and thanks to his intelligence and perseverance, he achieved a scholarship that allowed him to study at one of the best colleges in the country. In 1894, the future physicist became a Bachelor of Science.
He studied so well that he was awarded a personal scholarship and the right to continue his studies in England. Rutherford came to Cambridge and became a graduate student at the Cavendish Laboratory. There he continued to study the propagation of radio waves, and for the first time made radio communications at a distance of about a kilometer. But purely engineering problems never attracted him, and Rutherford began studying the conductivity of air under the influence of the newly discovered X-rays. This work, which he did together with J. J. Thompson, led to the discovery of the electron. After this, Rutherford began studying the structure of the atom.
After defending his doctoral dissertation, Resenford went to Canada and took a position as professor of physics at McGill University in Montreal. There he began to study radioactivity. Rutherford studied the properties of alpha and beta rays, and also discovered isotopes of thorium and radium. In 1908, Ernest Rutherford received the Nobel Prize for his theory about the transformation of radioactive elements. The scientist conducted this research together with F. Soddy.
In 1907, Rusenford returned to England, where he became head of the physics department at the University of Manchester. By studying the scattering of alpha rays, the scientist discovered the existence of atomic nuclei and determined their sizes. He did this work together with the future famous physicist Marsden. Based on these studies and the theoretical work of the Danish physicist Niels Bohr, the Bohr-Rutherford model of the atom was created.
In 1918, Rutherford made another major discovery - he proved the possibility of converting the nitrogen nucleus into oxygen under the influence of alpha particles, confirming the possibility of converting one chemical element into another.
While studying collisions of alpha particles with hydrogen atoms, Rutherford made another fundamental discovery - artificial radioactivity.
It is interesting that the scientist considered this a purely scientific problem and did not believe in the possibility of practical use of nuclear energy. Nevertheless, it was his collaborator, and later, the prominent German physicist Otto Hahn, who discovered the fission of uranium, and Rutherford’s work greatly brought the advent of the nuclear age closer. In 1919, Ernest Rutherford became director of the Cavendish Laboratory. He remained in this post until his death. The laboratory became a real Mecca for physicists of the 20th century. Many of the greatest scientists of our time, who considered themselves students of Rutherford, worked there - Blackett, Cockroft, Chadwick, Kapitsa, Walton. The scientist believed that the main thing is to give a person the opportunity to open up to the end and show what he is capable of. Thus, he initiated the construction of a special magnetic laboratory for P. Kapitsa’s experiments, and later achieved the sale of unique equipment in the USSR so that the scientist could continue his scientific work there.
Nobel Prize in Chemistry, 1908
English physicist Ernest Rutherford was born in New Zealand, near Nelson. He was one of 12 children of wheelwright and construction worker James Rutherford, a Scot, and Martha (Thompson) Rutherford, an English schoolteacher. First, R. attended primary and secondary local schools, and then became a scholarship student at Nelson College, a private higher school, where he showed himself to be a talented student, especially in mathematics. Thanks to his academic success, R. received another scholarship, which allowed him to enter Canterbury College in Christchurch, one of the largest cities in New Zealand.
In college, R. was greatly influenced by his teachers: E.U., who taught physics and chemistry. Bickerton and mathematician J.H.H. Cook. After R. was awarded a Bachelor of Arts degree in 1892, he remained at Canterbury College and continued his studies thanks to a scholarship in mathematics. The following year he became a Master of Arts, having passed the exams in mathematics and physics best of all. His master's thesis concerned the detection of high-frequency radio waves, the existence of which was proven about ten years ago. In order to study this phenomenon, he constructed a wireless radio receiver (several years before Guglielmo Marconi did) and with its help received signals transmitted by colleagues from a distance of half a mile.
In 1894, R. was awarded a bachelor's degree in natural sciences. It was a tradition at Canterbury College that any student who completed a Master of Arts degree and remained in college was required to undertake further studies and obtain a Bachelor of Science degree. Then R. taught for a short time at one of the boys' schools in Christchurch. Thanks to his extraordinary abilities for science, R. was awarded a scholarship to the University of Cambridge in England, where he studied at the Cavendish Laboratory, one of the world's leading centers of scientific research.
In Cambridge, R. worked under the guidance of the English physicist J.J. Thomson. Thomson was deeply impressed by R.'s study of radio waves, and in 1896 he proposed to jointly study the effect of X-rays (discovered a year earlier by Wilhelm Roentgen) on electrical discharges in gases. Their collaboration resulted in significant results, including Thomson's discovery of the electron, an atomic particle that carries a negative electrical charge. Based on their research, Thomson and R. hypothesized that when X-rays pass through a gas, they destroy the atoms of the gas, releasing equal numbers of positively and negatively charged particles. They called these particles ions. After this work, R. began studying atomic structure.
In 1898, R. accepted a position as a professor at McGill University in Montreal (Canada), where he began a series of important experiments concerning the radioactive radiation of the element uranium. He soon discovered two types of this radiation: the emission of alpha rays, which penetrate only a short distance, and beta rays, which penetrate a much greater distance. Then R. discovered that radioactive thorium emits a gaseous radioactive product, which he called “emanation” (emission - Ed.).
Further research showed that two other radioactive elements - radium and actinium - also produce emanation. Based on these and other discoveries, R. came to two important conclusions for understanding the nature of radiation: all known radioactive elements emit alpha and beta rays, and, more importantly, the radioactivity of any radioactive element decreases after a certain specific period of time. These findings gave reason to assume that all radioactive elements belong to the same family of atoms and that their classification can be based on the period of decrease in their radioactivity.
Based on further research conducted at McGill University in 1901...1902, R. and his colleague Frederick Soddy outlined the main provisions of the theory of radioactivity they created. According to this theory, radioactivity occurs when an atom loses a particle of itself that is ejected at great speed, and this loss transforms an atom of one chemical element into an atom of another. The theory put forward by R. and Soddy conflicted with a number of pre-existing ideas, including the long-accepted concept that atoms are indivisible and unchangeable particles.
R. conducted further experiments to obtain results that confirmed the theory he was building. In 1903, he proved that alpha particles carry a positive charge. Because these particles have measurable mass, "ejecting" them from the atom is critical to converting one radioactive element into another. The created theory also allowed R. to predict the speed at which various radioactive elements would turn into what he called daughter material. The scientist was convinced that alpha particles were indistinguishable from the nucleus of a helium atom. Confirmation of this came when Soddy, then working with the English chemist William Ramsay, discovered that radium emanations contained helium, the putative alpha particle.
In 1907, P., trying to be closer to the center of scientific research, took the post of professor of physics at the University of Manchester (England). With the help of Hans Geiger, who later became famous as the inventor of the Geiger counter, R. created a school for the study of radioactivity in Manchester.
In 1908, R. was awarded the Nobel Prize in Chemistry “for his research in the field of the decay of elements in the chemistry of radioactive substances.” In his opening speech on behalf of the Royal Swedish Academy of Sciences, K.B. Hasselberg pointed out the connection between the work carried out by P. and the work of Thomson, Henri Becquerel, Pierre and Marie Curie. “The discoveries led to a stunning conclusion: a chemical element... is capable of transforming into other elements,” Hasselberg said. In his Nobel lecture, R. noted: “There is every reason to believe that the alpha particles that are so freely ejected from most radioactive substances are identical in mass and composition and must consist of the nuclei of helium atoms. We cannot, therefore, help coming to the conclusion that the atoms of the basic radioactive elements, such as uranium and thorium, must be constructed, at least in part, from atoms of helium.”
After receiving the Nobel Prize, R. began studying the phenomenon that was observed when a thin gold foil plate was bombarded with alpha particles emitted by a radioactive element such as uranium. It turned out that using the angle of reflection of alpha particles it is possible to study the structure of the stable elements that make up the plate. According to the then accepted ideas, the model of the atom was like raisin pudding: positive and negative charges were evenly distributed inside the atom and, therefore, could not significantly change the direction of motion of alpha particles. P., however, noticed that certain alpha particles deviated from the expected direction to a much greater extent than was allowed by theory. Working with Ernest Marsden, a student at the University of Manchester, the scientist confirmed that quite a large number of alpha particles were deflected further than expected, some at angles of more than 90 degrees.
Reflecting on this phenomenon, R. in 1911 proposed a new model of the atom. According to his theory, which has become generally accepted today, positively charged particles are concentrated in the heavy center of the atom, and negatively charged ones (electrons) are in orbit around the nucleus, at a fairly large distance from it. This model, like a tiny model of the solar system, assumes that atoms are composed mostly of empty space. Wide recognition of R.'s theories began in 1913, when the Danish physicist Niels Bohr joined the scientist's work at the University of Manchester. Bohr showed that in terms of the structure proposed by R., the well-known physical properties of the hydrogen atom, as well as the atoms of several heavier elements, can be explained.
When the First World War broke out, R. was appointed a member of the civilian committee of the Office of Invention and Research of the British Admiralty and studied the problem of locating submarines using acoustics. After the war he returned to the Manchester laboratory and in 1919 made another fundamental discovery. While studying the structure of hydrogen atoms by bombarding them with high-velocity alpha particles, he noticed a signal on his detector that could be explained as the result of the nucleus of a hydrogen atom being set in motion by a collision with an alpha particle. However, exactly the same signal appeared when the scientist replaced hydrogen atoms with nitrogen atoms. R. explained the reason for this phenomenon by the fact that bombardment causes the decay of a stable atom. Those. In a process similar to the naturally occurring decay caused by radiation, an alpha particle knocks out a single proton (the nucleus of a hydrogen atom) from the normally stable nucleus of a nitrogen atom and imparts monstrous speed to it. Further evidence in favor of this interpretation of this phenomenon was obtained in 1934, when Frédéric Joliot and Irène Joliot-Curie discovered artificial radioactivity.
In 1919, R. moved to the University of Cambridge, becoming Thomson's successor as professor of experimental physics and director of the Cavendish Laboratory, and in 1921 he took the position of professor of natural sciences at the Royal Institution in London. In 1930, R. was appointed chairman of the government advisory council of the Office of Scientific and Industrial Research. Being at the top of his career, the scientist attracted many talented young physicists to work in his laboratory in Cambridge, incl. P.M. Blackett, John Cockcroft, James Chadwick and Ernest Walton. Despite the fact that this left R. himself with less time for active research work, his deep interest in the research being carried out and clear leadership helped maintain a high level of work carried out in his laboratory. Students and colleagues remembered the scientist as a sweet, kind person. Along with the gift of foresight inherent in him as a theorist, R. had a practical streak. It was thanks to her that he was always accurate in explaining observed phenomena, no matter how unusual they might seem at first glance.
Concerned about the policies pursued by the Nazi government of Adolf Hitler, R. in 1933 became president of the Academic Relief Council, which was created to assist those who fled Germany.
In 1900, during a short trip to New Zealand, R. married Mary Newton, who bore him a daughter. He enjoyed good health almost until the end of his life and died in Cambridge in 1937 after a short illness. R. is buried in Westminster Abbey near the graves of Isaac Newton and Charles Darwin.
Among the awards received by R. are the Rumford Medal (1904) and the Copley Medal (1922) of the Royal Society of London, as well as the British Order of Merit (1925). In 1931, the scientist was granted a peerage. R. was awarded honorary degrees from New Zealand, Cambridge, Wisconsin, Pennsylvania and McGill universities. He was a corresponding member of the Royal Society of Göttingen, as well as a member of the New Zealand Philosophical Institute and the American Philosophical Society. The Academy of Sciences of St. Louis, the Royal Society of London and the British Association for the Advancement of Science.
Nobel Prize laureates: Encyclopedia: Trans. from English – M.: Progress, 1992.
© The H.W. Wilson Company, 1987.
© Translation into Russian with additions, Progress Publishing House, 1992.
