The fourth periodic elements are potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, bromine and krypton. The periodic table of chemical elements is a list of chemical elements in descending order of atomic number. The list is generally rectangular, and some elements have spaces in the period, so that elements with similar characteristics belong to the same family, such as alkali metal elements, alkaline earth metals, halogen elements and rare gases.

This makes the periodic table divided into seven main families, seven sub-families, eight families and zero families. 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.

Contents of the periodic table of elements

Russian chemist dmitri mendeleev invented the first generation periodic table in 1869. Since then, 170 various types of periodic tables have appeared, which can be summarized as: short table represented by Mendeleev, long table represented by Werner type, long table represented by Baltar type, plane spiral table and circular table represented by Damkev type, and three-dimensional period.

The periodic law of elements in modern chemistry was first founded by Russian scientist Mendeleev in 1869. He arranged 63 kinds of 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 of elements. 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 series. The atomic radius decreases from left to right and increases from top to bottom.