Last time we said that Bohr published three papers on the structure of atoms in July, September and November 1913, and the title of these three papers was the same, called "On the Structure of Atoms and Molecules", so history called "Trilogy".
After the first paper was published in July, the university of Copenhagen, the only university in Denmark and Bohr's alma mater, offered Bohr the position of non-staff lecturer, that is, there was no career editor, which was not to be counted, and they actually asked Bohr to teach some elementary physics knowledge to non-physics students.
Although Bohr was very unhappy, he also accepted the position temporarily, because the place where he now worked was not even a university, it was a technical college, but Bohr was now holding back his big move.
After Bohr's second paper was published in September, just in time for the 83rd British Association for the Advancement of Science conference, there were many names of the participants, we are very familiar with, such as: Lorenz, Marie Curie, Ehrenfest, Laue, of course, but also several british predecessors, Thomson, Rutherford, Ruili;
Bohr also went to the meeting, after all, England was no stranger to him, and he could meet his teacher. At this meeting, Bohr's latest quantitative atomic model was rightly discussed.
But everyone except Rutherford opposed Bohr's idea for the simple reason that they were convinced that Maxwell's theory should hold true in all cases. Bohr, on the other hand, said that electrons do not emit radiation as long as they are in a particular orbit.
You may also want to ask: Why don't electrons emit radiation in a particular orbit? I can only answer that there is no why, because the world is quantized, it is not continuous, electrons can only exist in these orbits, can not exist in any other space, since it can not exist in other space, then these orbits are naturally stable state orbitals.
In fact, to put it bluntly, as long as you accept that the world is intermittent, there will be no such confusion. In quantum theory, there are a lot of questions you can't ask why? Just accept.
In later videos, you'll come across more and more questions that you can't ask why. This is where quantum mechanics struggles.
But Bohr could not say to other physics in such a tone, don't ask me why, just accept. Newton had never been so bullish, so experiments were needed to continue testing Bohr's model of quantized atoms to see if what he called a discrete energy level existed. As long as it does exist, it can show that Bohr is right.
Just in November 1913, when Bohr's third paper was published, one member of Rutherford's team, Henry Mosley, was inspired by Bohr's atoms to bombard various elements with electrons and study the X-rays released by the elements.
In fact, Bohr went to this colleague in July and asked him to quickly do experiments to verify his atomic theory. After listening to Bohr's theory, Mosley was also quite interested and began to experiment.
According to Bohr's theory, electrons of sufficient energy bombarding a particular metal element can release X-rays because an electron in the ground state of the atom is knocked out, and the electrons in the upper layer jump downwards, releasing the energy difference between the two energy levels in the form of X-rays.
And according to Bohr's atomic model and the frequency of the X-rays released, the nuclear power charge in the elemental nucleus can also be calculated.
Mosley spent two months bombarding from calcium all the way to zinc, and then continuing to bombard, and as more and more elements were bombarded, he found that the order of the elements in the periodic table was indeed arranged according to the nuclear power charge, which verified Bohr's earliest conjecture about the concept of atomic number.
And Mosley also found that the X-ray wavelength released by each element is unique, and the X-ray wavelength between the two adjacent elements is very close, because they only have a nuclear charge difference between them, and if the X-ray wavelength difference is relatively large, it means that there are other unknown elements in the middle.
So Mosley predicted 42, 43, 72, 75, these four new elements. It wasn't long before all four elements were discovered, but mosley died in World War I in 1915.
World War I broke out in 1914, when all the young people who could participate in the battle went to the battlefield, scientists could not stay out of it, and colleagues who had just been doing experiments together in the laboratory became enemies on the battlefield with guns in the blink of an eye.
For example, Geiger, Marsden, and Hévesy, mentioned earlier, participated in World War I, and de Broglie and Schrödinger, which we will talk about later, were also serving their own countries.
Even Rutherford had no effort to study atoms at this time, and he was more concerned with how he could sink German submarines.
We go on to say that in April 1914, the Bohr atomic model ushered in another key piece of evidence; the German physicists James Frank and Gustav Hertz, who was the nephew of hertz,
When they bombarded the mercury atom with electrons, they found that as long as the mercury atom released ultraviolet light, the electron used to bombard the mercury atom would lose 4.9 ev of energy.
Bohr's theory can perfectly explain this experiment, 4.9ev is the energy difference between the first excited state and the ground state of the mercury atom, as long as the electron used to bombard the mercury atom exceeds this energy, it is possible to hit the ground state electron, and the electron of the first excited state jumps downward, and the electromagnetic radiation of the corresponding energy is released. Using the Planck-Einstein formula, it is possible to calculate that the wavelength of this electromagnetic radiation is 253.7 nanometers, located in the ultraviolet band.
Bohr's theory and experiment coincided very well, and this experiment became the strongest evidence for verifying Bohr's atomic model, and with Mosley's work, by the end of 1914, almost everyone had accepted Bohr's quantitative atomic model in the face of experimental evidence. Bohr's discrete energy levels, quantization of electron angular momentum, and interpretation of elemental spectra were accepted.
As Bohr's fame in the scientific community grew, Bohr finally said what he had been hiding in his heart for a long time, and he said to the management of the University of Copenhagen, you see I am now a physicist, it is not appropriate to be a lecturer, can I give a position as a professor of theoretical physics.
The university management listened and was a little confused. Professor of Theoretical Physics? This position has never been held since its founding, and this is to open a new discipline for Bohr, in fact, at that time, in addition to the German universities, there were really very few universities to establish this position, even in Germany, there were very few people specializing in theoretical physics.
Theoretical physicists are relatively simple to work compared to experimental physicists, take Einstein, when he decided to work in Prince in the United States for a long time, it was already 1934, when Einstein's reputation was global, and he could be on a par with Copernicus, Bruno, and Newton. We'll buy it for you, Einstein said, a desk, a pen, and some paper.
This is the standard three-piece set of theoretical physicists, which does not require cumbersome experimental equipment, but today, theoretical physics is inseparable from experiments and observations, and it no longer distinguishes between theorists and experimenters.
Bohr's request was not approved, and even if Rutherford wrote to the Ministry of Education many times, the reply was to slow down. It was impossible for Bohr to continue to be a lecturer, so Bohr took a leave of absence to go to Manchester to find Rutherford, and heard that Rutherford was going to reintroduce him to work.
However, the matter was delayed due to the war, and Bohr remained in Manchester for a long time, until May 1916, when the University of Copenhagen agreed to Bohr's request and created him a special position as a professor of theoretical physics.
Because during this period, another thing happened that made Bohr's reputation rise again, and Copenhagen had to seriously consider Bohr's request.
Because Sommerfeld of the University of Munich not only fully accepted Bohr's atomic theory, but also further introduced two quantum numbers on this basis, the orbital shape quantum number K, also called the angle quantum theory and the orbital direction quantum number M, also called magnetic quantum beam. Explaining the fine structure of the Balmormites that people cannot explain, the fine structure constants were found, as well as the Stark and Zeyman effects.
This is the content of our next video.