What Are Nuclides?

A nuclide is an atom with a certain number of protons and a certain number of neutrons. Nuclei with different nuclear properties of the same isotope have the same number of protons but different numbers of neutrons, and have different structures, so they show different nuclear properties.

Chinese name: Nuclide
Foreign name: nuclide

Applied discipline: Physical Chemistry
Scope of application: Quantum physics

Introduction to Nuclides

A nuclide is an atom with a certain number of protons and a certain number of neutrons. Many elements have several atoms with the same number of protons but different numbers of neutrons. For example, hydrogen has 3 atoms of 1H, 2H, and 3H, which are three kinds of nuclides, and their nuclei have 0, 1, and 2 neutrons, respectively. These three nuclides are called isotopes. ^[1] For example, there are 6 protons and 6 neutrons in the nucleus. The mass number is 12, which is called carbon-12 nuclide, or written as 12C nuclide. There are 6 protons and 7 neutrons in the nucleus. The mass number is 13, which is called 13C nuclide. There are three kinds of nuclide 16O, 17O, 18O. Elements with multiple nuclides are called multinuclides. The only element that exists in nature is called a single nuclide element, such as 20 elements such as beryllium, fluorine, aluminum, and sodium. ^[2] An element with an even number of protons may have more stable nuclides, generally no less than 3 kinds, and an element with an odd number of protons, usually has only one stable nucleus, generally no more than two, this It is determined by the binding energy of the nucleus. Multinuclides are called isotopes because they are at the same position in the periodic table. They have basically the same chemical properties but different nuclear properties; single nuclide elements have no isotopes. The mass of a nuclide, that is, the atomic mass, is always less than the sum of the masses of isolated protons, neutrons and electrons, and is not conceptually equal to the mass number. It is slightly different from the mass number except for 12C. The quality of the nuclide is determined by mass spectrometer. This kind of measurement is very advanced. It can measure 7 or more significant figures.

Nuclide concept introduced

The concept of a nuclide was originally introduced to exactly describe the atomic weight of an element. The original concept of a chemical atom was an element atom, that is, the same element corresponds to the same atom, so the atomic weight of an element is specified as the relative mass of the element atom. The discovery of isotopes reveals that elements are not a type of atom with the same chemical properties and quantities. The atoms of the same element can have different masses. Therefore, the atomic weight of an element reflects the average of the masses of various isotopes. Studies in atomic physics have further shown that the mass of an atom is mainly determined by the number of protons and neutrons that make up the nucleus, and the chemical properties of the elements are only related to the number of protons. To further distinguish the isotopes of the elements, scientists introduced the mass number of the isotope, which is the sum of the number of protons and neutrons. From the chemical properties of the elements, different isotopes are in the same position on the periodic table of the elements, so they are called "isotopes". From the perspective of the nuclei, isotopes are nuclei with different masses of the same element, also called nuclide. At this time, the nuclide is just another name for an isotope. Later, it was discovered that the naturally occurring and artificially produced nuclei on the earth have the phenomenon of "isonuclear energy state", that is, the nuclear properties exhibited by nuclei with the same number of protons and neutrons, such as decay mode, half-life, energy, etc Etc can be different. Homonuclear states are "isomers" at the nucleus level. "Isomorphisms" refer to the same number of protons and neutrons. "Isomeric" means that they form the nucleus in different ways. But the concept of isotope is not enough to reflect this kind of "isomerism". If the concept of nuclide is defined as atomic nuclei with different nuclear properties of the same isotope, the phenomenon of nuclear isomerism can be summarized. Therefore, nuclide has become an independent concept to express nuclear properties.

Nuclide relationship

Nuclide Review

Nuclide and its symbol ; the relationship between atomic number , mass number and neutron number :

An atomic nucleus or atom with a certain number of nuclear charges and masses and having the same energy state is called a nuclide .

Nuclide commonly used symbols AZX, where X is the element symbol , Z is the atomic number , A is the mass number , AZ = N , N is the number of neutrons in the nuclide. Since the element symbol X has determined its atomic number, usually the nuclides can also be abbreviated as AX.

Scientific research shows that the stable nuclides have a certain limit on the total number of nucleons (generally A209), and the number of neutrons and protons should be maintained at a certain ratio (generally N / Z = 1 1.5, with some exceptions). Any nuclide containing too many nuclei or inappropriate N / Z is unstable. Nuclides with A 209, that is, all nuclides after plutonium (Po) in the periodic table are radioactive (elements before plutonium, some nuclides also have radioactivity), they emit spontaneously alpha rays (That is, He nucleus), and changed into a new nucleus with a smaller A; or because the n / Z of the nuclide is inappropriate, the neutrons and protons in its nucleus will spontaneously transform each other, thereby changing the value of N / Z At the same time, a - (or +) particle is released. Almost all new nuclei generated after the nuclide decays are in an excited state. Such nuclei either spontaneously emit gamma photons and change to the ground state or a lower energy state, or continue to undergo alpha decay (or beta decay) until Into a stable nuclide.

Nuclide understanding

Nuclides are divided into different atoms and different atoms different atoms of the same element

Nuclide chemistry

An atom with a certain number of protons and a certain number of neutrons is called a nuclide, the symbol is

Nuclide (1) The concept of a nuclide defines an atom;

(2) Most elements include multiple nuclides, and some natural elements contain only one kind of nuclides;

(3) There are more types of nuclides than elements. There are more than 1,000 nuclides in the 112 elements currently found.

Nuclide Nuclide Map

The periodic table of chemical elements cannot express the content of nuclide, which requires an expression that is compatible with the concept of nuclide, that is, the nuclide diagram (see figure). In the nuclide diagram, nuclide is arranged in the order of increasing atomic number and mass number. In this sense the nuclide diagram is a further development of the periodic table. It arranges the nuclides with the same mass in a column, and the in-line from top to bottom is a team of isobaric nuclides; the isotope nuclides are arranged in an oblique order from the upper left to the lower right in order of increasing mass, and are protons. Nuclides with the same number; from the lower left to the upper right (or from the upper right to the lower left) are isoneutrons. The nuclide diagram focuses on depicting the properties of atomic nuclei, such as decay mode, half-life, thermal neutron cross section, and ray properties. And energy, while omitting the nuclear electron shell structure. The modern theory of the periodic system of chemical elements and the theory of the outer shell structure of electrons are equivalent. How to further develop the periodic table of modern chemical elements to super heavy elements is essentially a question to be answered by the theory of the periodic system of nuclide. The magic number nuclide theory, which is based on the nucleus-shell structure model, describes the stability of the nuclide to a certain extent, thus revealing the inherent regularity of the nucleus. However, the magic number theory is far from complete, accurate and convincing like the electron shell theory. That is to say, the application of quantum mechanics theory at the nuclear level has not been successful. Therefore, the nuclide diagram is only exploring the form of periodic nuclide diagrams. Initial attempts.

Exploring the law of nuclide involves the problem of elementary particles. The nuclide can be regarded as a group of elementary particles. The stability of the nuclide mainly depends on the determined combination of neutrons and atoms. In the process of artificial nuclides, the mystery of the interaction and transformation of various elementary particles is far from fully understood.

Elements have lost their significance as the basis of all things in the world, and now human understanding has entered the level of basic particles as elemental components. The concept of nuclide may play a special role in understanding the material structure chain connecting element atoms and elementary particles.