This makes the periodic table of elements divided into 7 main groups, 7 sub-groups, 8 groups and 0 groups. Because the periodic table of elements can accurately predict the characteristics of various elements and their relationships, it is widely used in chemistry and other scientific fields as a very useful framework for analyzing chemical behavior.
Russian chemist dmitri mendeleev invented the periodic table in 1869. Since then, there have been 170 types of periodic tables, which can be summarized as: short table (represented by Mendeleev), long table (represented by Werner type) and super-long table (represented by Baltar type); Plane spiral table and circular table (represented by Damkoff type); Three-dimensional periodic table (represented by Lacey's cone-column three-dimensional table) and so on.
Long periodic table has been used for a long time in teaching in China.
Development history
The periodic law of elements in modern chemistry was first established by Russian scientist dmitri mendeleev in 1869. He arranged 63 elements known at that time in the form of tables according to their relative atomic masses, and put elements with similar chemical properties in the same column, making the prototype of the periodic table.
After years of revision, it has become a contemporary periodic table. In the periodic table of elements, the elements are arranged in atomic order, with the smallest one at the front. One row in the table is called period and one column is called family.
The atomic radius decreases from left to right and increases from top to bottom.
There is a "periodic table" in chemistry textbooks and dictionaries. This table reveals the secrets of the material world, unifying some seemingly unrelated elements to form a complete natural system. Its invention is a pioneering work in the history of modern chemistry, which has greatly promoted the development of chemistry. When people see this watch, they will think of its earliest inventor, Mendeleev.
1869, Russian chemist Mendeleev arranged elements with similar chemical properties in the same column according to the relative atomic mass from small to large, and compiled the first periodic table of elements. The periodic table of elements reveals the internal relations between chemical elements, making it a complete system and one of the important milestones in the history of chemical development.
With the development of science, the vacancies left by unknown elements in the periodic table have been filled one after another. When the mystery of atomic structure was discovered, the arrangement changed from the relative atomic weight to the proton number of atoms (the number of electrons outside the nucleus or the number of nuclear charges), and the current periodic table of elements was formed.
Number the elements according to their order in the periodic table to get the atomic number. The atomic number has the following relationship with the atomic structure of an element:
Proton number = atomic number = extranuclear electron number = nuclear charge number
Using the periodic table of elements, Mendeleev successfully predicted the characteristics of elements (gallium, scandium and germanium) that had not been discovered at that time. 19 13 British scientist Moseler hit the metal with cathode rays to generate X-rays, and found that the greater the order of atoms, the higher the frequency of X-rays. Therefore, he thinks that the positive charge in the nucleus determines the chemical properties of elements, and arranges elements according to the positive charge in the nucleus (that is, the number of protons or the atomic order). Later, it was revised by many scientists for many years before the contemporary periodic table was formed.
Elements are arranged in order of relative atomic mass from small to large, and elements with similar chemical properties are placed in one column. Each element has a serial number, which is exactly equal to the number of protons in the nucleus of the atom of the element. This serial number is called atomic number. In the periodic table of elements, the elements are arranged in atomic order, with the smallest one at the front. One row in the table is called period and one column is called family.
The distribution and properties of atoms' extranuclear electrons have obvious regularity. Scientists arrange elements with the same number of electrons in the same row and elements with the same number of electrons in the outermost layer of the same column.
The periodic table of elements has seven periods, 16 families. Each row is called a period, and each column is called a family (family VIII B contains three columns). These seven periods can be divided into short-term (1, 2, 3) and long-term (4, 5, 6, 7). There are 16 families, and each column from left to right counts as a family (except VIII B family). For example, hydrogen belongs to group I A, while helium belongs to group 0.
The position of elements in the periodic table not only reflects the atomic structure of elements, but also shows the gradual change law of element properties and the internal relations between elements. Making it a complete system is called one of the important milestones of chemical development.
In the same period, from left to right, the number of electron layers outside the nucleus of elements is the same, the number of outermost electrons increases in turn, and the atomic radius decreases (except for the zero group elements). The ability to lose electrons is gradually weakened, the ability to gain electrons is gradually enhanced, the metallicity is gradually weakened, and the nonmetal is gradually enhanced. The highest positive oxidation number of elements increases from left to right (except those without positive valence), and the lowest negative oxidation number increases from left to right (except O and F elements in the first and second periods).
In the same family, from top to bottom, the number of electrons in the outermost layer is the same, the number of layers of electrons outside the nucleus increases gradually, the atomic radius increases, the atomic number increases, the metallic nature of elements increases, and the nonmetallic nature decreases.
The periodic table of elements is of great significance, and scientists use it to discover new elements and compounds.
The website of 20 15 12 3 1 American science news biweekly published a report entitled "Four elements get permanent seats in the periodic table of elements". The International Union of Pure and Applied Chemistry (IUPAC) announced that Russian and American research teams had obtained sufficient evidence to prove that they had discovered the elements 1 15, 1 17 and 1 18.
In addition, the Federation acknowledged that researchers from Japan Institute of Physical Chemistry had discovered the element 1 13. The two research groups synthesized the above four elements by colliding the lighter nuclei with each other and tracking the decay of the radioactive overweight elements produced afterwards. Lynn Seby, executive director of IUPAC, said that the new element confirmation report will be published in early 20 16.
Official recognition of these elements means that their discoverers have the right to name and design symbols. 1 13 will be the first element discovered and named by Asians. It was officially named Nihonium on June 20 16 with the symbol Nh.
20 15, 1 13, 1 15,17, 1 18 by the international union of pure and applied chemistry. IUPAC officially announced that four new elements have been added to the periodic table.
On June 8, 20 16, the international union of pure and applied chemistry announced that the synthetic chemical element no. Added 1 13 (abbreviated as Nh), 1 15 (Mc),1/7 (Ts) and 65447 (TS).
References:
Periodic Table of Chemical Elements-Baidu Encyclopedia