The periodic law of elements in modern chemistry was pioneered by the Russian scientist Dmitri Mendeleev in 1869. He arranged the 63 elements known at that time in the form of a table according to their atomic weights, and placed elements with similar chemical properties in the same row, which was the prototype of the periodic table of elements tbw100.com/17.
Using the periodic table, Mendeleev successfully predicted the properties of elements that had not been discovered at that time (gallium, scandium, and germanium). In 1913, the British scientist Moselle used cathode rays to hit metals to produce X-rays. He found that the greater the atomic number, the higher the frequency of X-rays. Therefore, he believed that the positive charge of the nucleus determined the chemical properties of the elements, and arranged the elements according to the positive charge in the nucleus (i.e., the number of protons or atomic order). After many years of revision, it became the contemporary periodic table.
Chemical elements in the periodic table are arranged according to their atomic number, with the smallest ones listed first. A horizontal row in the table is called a period, and a column is called a family.
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