Development Of Periodic Table

J.W. Dobereiner ( 1780 - 1849 )

• Law of Triads ( 1817)

  • In groups of 3 --> Organized based on Atomic Weight & similar properties

J.A.R. Newlands ( 1837-1898 )

• Law of Octaves ( 1865 )

  • When organized by atomic weight, he noticed that elements have similar properties in 7 intervals. ( Octaves of 7 elements )

Lothar Meyer ( 1864 )

• Organized 28 elements into 6 different families with having similar Physical & Chemical Properties.

• Used the Valence Electrons to help organize and keep the families maintained in a set pattern ( Not specified how )

Dmitri Mendeleev ( 1834 - 1907 ) :

• Periodic Law (1869 )

  • Elements were sorted by Atomic Weight

    • Similar Physical & chemical properties.

  • Able to predict existence & properties of other elements

Henry Mosely ( 1887 - 1915 )

• Modern Periodic Table ( 1913 )

  • Arranged in order of increasing atomic number ( Z )

    • Properties recurred periodically