Element symbol: C. Because carbon, hydrogen, oxygen and nitrogen are the most common elements in organic compounds and organisms, it is more convenient to study organic chemical reactions and biochemical reactions by using non-radioactive 13C as tracer atoms, so it is widely used.
Carbon-13 (13c) (13 is written in the upper left corner of c) is an isotope of carbon. Its nucleus contains 6 protons and 7 neutrons (more than the common carbon 12 1 neutron), and there are 6 extranuclear electrons outside the nucleus, which is neutral. Carbon in nature contains two stable isotopes,13c1.1%and 12C 98.89%.
Because carbon, hydrogen, oxygen and nitrogen are the most common elements in organic compounds and organisms, it is more convenient to study organic chemical reactions and biochemical reactions with non-radioactive 13C as tracer atoms, so it is widely used. The most effective method to separate 13C is low temperature distillation of carbon monoxide, but it needs to be operated at 70 ~ 85K. In 1970s, another method was developed, that is, the chemical exchange method of carbon dioxide/carbamate system, which can be operated at normal temperature and pressure, and has always been regarded as the most promising method to produce 13C.
At the same time, there are different opinions on carbon 13 in medicine. The full name of carbon 13 is carbon 13 urea breath test, which belongs to the detection method of helicobacter pylori. It is a non-invasive examination, which is widely used in clinic. Because it is not necessary to prepare for the invasive examination of gastroscope, patients should be required to see a doctor on an empty stomach during the operation, and proton pump inhibitors, including H2 receptor blockers, should be avoided for two weeks before the trial.
Blow 1 breath on an empty stomach, then eat 1 tablet of urea. Urea does not contain carbon 12 in air, but contains carbon 13 or carbon 14. After 0.5 hours, the second breath is blown, which can be detected by instruments, and the carbon 65438 contained in the first two blows can be obtained.
Chemical element interpretation
Chemical elements are a kind of atoms with the same nuclear charge (the number of protons in the nucleus). From the philosophical point of view, elements are the result of qualitative change caused by quantitative change of proton number in atoms. Common elements are hydrogen, nitrogen and carbon. Up to 20 19, * * 1 18 elements have been discovered, among which 94 elements exist on the earth.
In chemistry, an element refers to a kind of atoms with the same nuclear charge number (or proton number). In mathematics, elements are the elements that make up a set and each object. If it is a general term for molecules or atomic groups with the same number of protons, it must not be the same element. Although they have the same number of protons, their generic terms must not belong to the same element.
It refers to 100 kinds of basic metals and nonmetallic substances in nature. They are composed of only one kind of atom, and their nuclei have the same number of protons. Can't be decomposed by ordinary chemical methods, but can form all substances. The nuclei of elements with atomic number ≥83 (bismuth and above) are unstable and will decay. Elements 43 and 6 1 (technetium and promethium) have no stable isotopes and will decay. The heaviest element in nature is 93 neptunium.