Mendeleev & the Periodic Table

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…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.