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The periodic table was developed by Dmitry Mendeleev in 1869. It classifies the elements according to their properties and increasing atomic weight. The atomic number, which identifies an element’s position in the periodic table, is equal to the amount of protons in the nucleus. From spaces in his table, Mendeleev was able to predict the existence of elements not yet discovered. Dmitry Mendeleev was a Russian chemist, best known for his development of the periodic …

…organising principle of the elements. Certain changes have since been made to the periodic table. For example, with the discovery of the electron, and the configurations of the electrons around the atoms of different elements, it became apparent that the arrangement of electrons varied periodically throughout the table. The modern periodic table lists the elements in order of their increasing atomic number, but it organises them into periods and groups according to their electron configurations.