Periodic Table
An arrangement of elements in a geometric pattern designed to represent the periodic law by aligning elements into periods and groups. Elements with the same number of orbitals are in the same period and elements with the same number of electrons in the filling orbital and have other similar properties are in the same group.
Dmitri Mendeleev, a Russian chemist, is credited as the primary creator of the first periodic table. He made a formal presentation to the Russian Chemical Society on March 6th 1869.