Because not all elements were then known, there were gaps in his periodic table, and Mendeleev successfully used the periodic law to predict properties of some of the missing elements. ![]() The first periodic table to become generally accepted was that of the Russian chemist Dmitri Mendeleev in 1869: he formulated the periodic law as a dependence of chemical properties on atomic mass. The underlying reason for these trends is electron configurations of atoms. ![]() Trends run through the periodic table, with nonmetallic character (keeping their own electrons) increasing from left to right across a period, and from down to up across a group, and metallic character (surrendering electrons to other atoms) increasing in the opposite direction. Elements from the same column group of the periodic table show similar chemical characteristics. ![]() The rows of the table are called periods, and the columns are called groups. The table is divided into four roughly rectangular areas called blocks. It is a graphic formulation of the periodic law, which states that the properties of the chemical elements exhibit a periodic dependence on their atomic numbers. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of chemistry. ![]() The periodic table, also known as the periodic table of the ( chemical) elements, is a tabular display of the chemical elements.
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