History of the Periodic Table
Dimitri Mendeleev published the first periodic table in 1869. At this point, we only knew of approximately 63 elements. Mendeleev arranged these elements according to their atomic mass and the elements' properties. He also left empty spaces in his table which predicted the existence of more elements that were not discovered yet. Mendeleev accomplished all of this without knowledge of electron or proton which were discovered in 1897 and 1911.
In 1914, Mosely rearranged the table according to atomic number as well as the element properties, which is how it is organized today. This revision led to the periodic law- The properties of elements repeat periodically when they are arranged by increasing atomic number. Later discoveries explained why the properties of elements repeated and why the table looks the way it does. The actinides section was added in the 1940's by Glenn Seaborg.
In 1914, Mosely rearranged the table according to atomic number as well as the element properties, which is how it is organized today. This revision led to the periodic law- The properties of elements repeat periodically when they are arranged by increasing atomic number. Later discoveries explained why the properties of elements repeated and why the table looks the way it does. The actinides section was added in the 1940's by Glenn Seaborg.