Are there any short stories about chemists exploring the structure of atoms?

Rutherford, who revealed the inside story of the atom

Rutherford was born in Nelson, New Zealand, on August 30, 1871. He graduated from the University of New Zealand and the University of Cambridge. In 1898, he went to Canada as a professor of physics at Macchier University and stayed there for nine years. During this period, he made great contributions to the research on radioactivity. In 1907, he was appointed professor of physics at the University of Manchester. He won the Nobel Prize in Chemistry in 1908 for his research on radiochemistry. In 1919, he was appointed professor at Cambridge University and director of the Cavendish Laboratory. In 1931 the King of England awarded him the title of Lord. Died on October 19, 1937.

At the end of the 19th century, "three major discoveries" broke out in physics that shocked the scientific community: In 1895, the German physicist R?ntgen discovered X-rays, and in the same year, the French physicist Becquerel discovered Natural radioactivity was discovered; in 1897, British physicist Thomson (1859-1940) discovered the electron. These great discoveries inspired Rutherford and made him determined to conduct in-depth research on atomic structure.

In 1899, Rutherford used a strong magnetic field to act on the rays emitted by radium. He discovered that the rays could be divided into three components. He called the positively charged part with a small deflection amplitude a-ray, and the negatively charged part with a large deflection amplitude called b-ray. The third part was not deflected in the magnetic field and had strong penetrating power. He called it r-ray.

In 1903, Rutherford confirmed that a-rays are a flow of positive ions (helium nuclei) with the same mass as the element helium, while b-rays are a flow of negatively charged electrons. Rutherford also called a-rays a-particles. He further used experiments to prove that when a-rays hit a fluorescent screen coated with zinc sulfide, they will emit a flash. Therefore, he used this phenomenon to create a scintillation mirror that could observe crystal particles.

Rutherford further studied the penetrating power of oral rays. He found that most a-particles can penetrate thin metal foil, and these particles are "like entering no one's land" in the metal foil. , can pass with swagger. This phenomenon shows that the atoms in the solid are not airtight, the arrangement is not tight, and there are many gaps inside, so the a particles can pass through the metal foil without changing direction.

The experiment found that when a small number of a particles passed through the metal foil, they seemed to be squeezed by something, so their trajectory was deflected at a certain angle. There are also individual particles that seem to bounce back completely as if they were hit head-on on something hard. Based on the above experimental phenomenon of a particles passing through metal foil (this experiment is called an a particle scattering experiment), Rutherford imagined that there must be a positively charged hard core inside the atom, and the a particles would be struck when they hit the nucleus. When it bounces back, it will change direction and deflect at a certain angle when it hits the target. The nucleus of an atom occupies a very small space, so most a particles can still pass through. Based on this assumption, he calculated that the radius of the nucleus is about 3×10-12 cm, while the radius of the atom is 1.6×10-8 cm.

In 1911, inspired by the "similarity between the macrocosm and the microcosm", Rutherford compared the solar system to the atomic structure and proposed an atomic model. He believed that atoms are like a small solar system. Each atom has a very small nucleus with a diameter of about 10-12 centimeters. This nucleus contains almost all the mass of the atom and carries a positive charge of one unit. The nucleus There are electrons outside rotating around the nucleus, so under normal circumstances, the atom is neutral.

After Rutherford discovered the atomic nucleus, he further conducted "particle scattering experiments" with various metals and found that different metal pairs have different scattering abilities of particles. The stronger the scattering ability, the stronger the positive charge of the nucleus. The more, the greater the repulsion. In 1913, Rutherford's student and assistant Moseley, under Rutherford's guidance, proved that the charges carried by the nuclei of various elements were exactly equal to their atomic numbers. Rutherford's atomic model successfully explained many physical and chemical phenomena, but later research found that it had great limitations. His student, Danish physicist Nelson Bohr, synthesized Planck's quantum theory and Einstein's photon theory, and proposed the Bohr model of the atom based on Rutherford's atomic model. This model It is a great improvement over the Rutherford model, but it is the product of a combination of classical mechanics and quantum theory. Therefore, with the development of science, many unrealistic situations have emerged, so it was later replaced by the quantum mechanics model.

Rutherford made outstanding contributions in nuclear chemistry. When he used alpha particle scattering to study atomic nuclei, he found that for light elements, abnormal phenomena often occurred. He thought at the time that it might be because the light nucleus had less nuclear charge and smaller repulsion, so high-speed a particles might overcome the repulsion and hit the light nucleus, causing abnormalities. Later, he conducted in-depth research on this idea. Rutherford first selected the strongest radioactive source, called radium C' at the time, which was actually 204Po, to bombard light elements. In 1919, when he bombarded nitrogen with alpha particles, he discovered that a new particle with a long range and smaller mass was produced. Research proved that this particle was the nucleus of hydrogen. Rutherford named the particle he discovered "the proton."

In this experiment, he not only discovered protons, but also realized the first nuclear reaction in human history:

14N+4He——>17O+1H

Then he discovered , boron, fluorine, sodium, aluminum, phosphorus and other elements can undergo nuclear reactions. During nuclear reactions, one element can become another element. In 1920, Rutherford proposed the neutron hypothesis. He believed that in the nucleus, protons may be tightly combined with electrons to form an uncharged particle, a neutron. He speculated that because there is no electric field around a neutron, no ions should be produced when it passes through a gas. It is not affected by the force of the electric field, so the penetrating force will be very strong. It will only turn when it collides head-on with the atomic nucleus. The collided nucleus may be ejected at a certain speed because it has gained a certain kinetic energy.

Rutherford's prediction about neutrons was confirmed by Chadwick in 1932. He used a particles to bombard hinge elements and obtained neutrons:

9Be+4He ——>12C+1n

Rutherford’s research on radioactivity finally pointed out the possibility of atomic modification, realizing the dream of the alchemists before the Middle Ages. In addition, Rutherford also made a theoretical discussion on the phenomenon of natural nuclear fission. He believed that natural radioactivity was caused by the explosive splitting of basic atoms. Among the astronomical numbers of atoms, somewhere would suddenly explode, emitting various rays, and the remaining parts would become other atoms. If an a particle is ejected during the explosion, the atomic weight of this new element will be one helium atom less than before the explosion. In Rutherford's time, only the fission of heavy atoms was known, but it was not known that light atoms could be fused. Whether it was fission or fusion, energy could be released.

Rutherford was an upright man, devoted himself to science, and did not disdain the powerful. He was also a great educator and trained many first-class experts for mankind, such as Bohr, Moseley, etc. After Chi's death, people hold commemorative activities for him on October 19 every year.