Isotope popular science knowledge (Part 2)
- Categories:Technology
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- Time of issue:2022-04-28
(Summary description)In 1910, the British chemist Soddy put forward a hypothesis that there are variants of chemical elements with different relative atomic mass and radioactivity but the same physical and chemical properties. These variants should be in the same position of the periodic table, called isotopes.
Isotope popular science knowledge (Part 2)
(Summary description)In 1910, the British chemist Soddy put forward a hypothesis that there are variants of chemical elements with different relative atomic mass and radioactivity but the same physical and chemical properties. These variants should be in the same position of the periodic table, called isotopes.
- Categories:Technology
- Time of issue:2022-04-28
- Views:
Isotope popular science knowledge (Part 2)
【British chemist Soddy was the first person to put forward the concept of isotope】
In 1910, the British chemist Soddy put forward a hypothesis that there are variants of chemical elements with different relative atomic mass and radioactivity but the same physical and chemical properties. These variants should be in the same position of the periodic table, called isotopes. Soon, from different radioactive elements (uranium, thorium, etc.), the relative atomic mass of one kind of lead was 206.08, and that of the other was 208. 1897 British physicist Thomson (Joseph ˙ John ˙ Thomson) discovered electrons. In 1912, he improved the instrument for measuring electrons and made a magnetic separator (the predecessor of mass spectrometer) by using the action of magnetic field. When he measured with neon, no matter how purified neon was, two parabolas were obtained on the screen, one representing neon with a relative atomic mass of 20 and the other representing neon with a relative atomic mass of 22. This is the first stable isotope discovered, that is, the non radioactive isotope. After Aston made the first mass spectrometer, it was further proved that neon did have two isotopes with different atomic masses, and more than 200 isotopes were found in more than 70 other elements.
【According to Thomson's experimental diagram, the trace of neon is divided into two tracks, one bright and the other dark】
So far, 109 elements have been found, only 20 elements have no stable isotopes, but all elements have radioisotopes. Most natural elements are a mixture of several isotopes. There are more than 300 stable isotopes and more than 2800 radioactive isotopes.
After the neutron proton theory of atomic nucleus was put forward in 1932, it was further clarified that isotope is an element with several atoms with the same number of protons but different numbers of neutrons. Since the number of protons is the same, their nuclear charge and the number of extranuclear electrons are the same (proton number = nuclear charge number = number of extranuclear electrons), and they have the same electronic layer structure. Therefore, the chemical properties of isotopes are the same, but due to their different neutron numbers, the atomic masses are different, and some physical properties (such as radioactivity) related to atomic nuclei are also different. Generally speaking, elements with even number of protons can have more stable isotopes, and usually not less than 3. Elements with odd number of protons generally have only one stable nuclide, and their stable isotopes will never be more than two, which is determined by the binding energy of nucleons.
The discovery of isotopes has deepened people's understanding of atomic structure. This not only makes the concept of element have a new meaning, but also makes a significant change in the benchmark of relative atomic mass. It is once again proved that the number of protons (nuclear charges) rather than the number of atomic mass determines the chemical properties of elements.
Many isotopes have important uses. For example, 12C is used as an atom to determine the atomic weight standard; Two H atoms are the materials for making hydrogen bombs; 235U is the material for making atomic bombs and nuclear reactors. Isotope tracing method is widely used in scientific research (such as national defense), industrial and agricultural production and medical technology. For example, O-labeled compounds are used to confirm the process of esterification.
The peaceful use of nuclear energy is also an important part of the nuclear industry serving the national economy and people's lives. In 1982, the Ministry of nuclear industry established the China isotope company, which is responsible for organizing isotope production, supply and import and export trade. The Chinese nuclear society has established 19 chapters on Nuclear Agriculture, nuclear medicine, nuclear power, radiation technology and isotopes. It has also held many relevant professional meetings to promote the application of nuclear energy, isotopes and other nuclear technologies.
There are more and more varieties of isotopes that can be produced in China, including radiopharmaceuticals, various radioactive sources, labeled compounds such as hydrogen-3 and carbon-14, radiochemical agents, various kits for radioimmunoassay, stable isotopes and their labeled compounds. Among the isotope production units, the isotope production of the Chinese Academy of atomic energy accounts for more than 80% of the country's total. The domestic users of isotopes in China have gradually changed from mainly relying on imports in the past to being mostly self-sufficient through domestic production.
With the development of isotope production, the application of isotopes and other nuclear technologies in many sectors has been further promoted, and obvious economic and social benefits have been achieved. In agriculture, the radiation method or the combination of radiation and other methods has been used to cultivate good varieties of crops, which has greatly increased the yield of crops such as grain, cotton and soybeans. Using isotope tracer technology to study the rational use of pesticides and chemical fertilizers and soil improvement provide new measures for agricultural production. Other research work, such as radiation preserved food, has also made great progress. In medicine, there are thousands of medical units in China, and more than 100 isotope therapy methods have been established in clinic, including external irradiation therapy and internal drug irradiation therapy. Isotopes also play an important role in immunology, molecular biology, genetic engineering research and the development of basic nuclear medicine.
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