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Johann Dobereiner- Model of Triads
Dobereiner catergorised elements with similar characteristics into groups of threes. He called these groups "Triads". An example of a triad was: Calcium, Strontium and Barium, all of which are in Group I. -
John Newlands- Law of Octaves
After arraniging elements in order of increasing atomic mass, Newlands suggested that elements should be arranged in "octaves", after observing that some characteristics repeated every 8th element. An example of an octave was: Hydrogen, Lithium, Beryllium, Boron, Carbon, Nitrogen and Oxygen respectively. -
Dmitri Mendeleev- First Periodic Table of the Elements
Mendeleev published a table of elements arranged in order of increasing atomic mass. He left gaps for elements not yet discovered (for example Scandium, Gallium and Germanium) and predicted their properties. He also corrected the atomic masses of Beryllium, Indium and Uranium. -
Lothar Meyer- A Different Periodic Table
Meyer published his own table of elements at the same time as Mendeleev. It was also organised by increasing atomic mass. However Mendeleev is known as the "father of the periodic table", and Meyer is not; even though they both arranged the elements by increasing atomic mass and left gaps for undiscovered elements. The reason taht Mendeleev is credited is because he predicted correctly the characteristics of these undiscovered elements. -
Henry Moseley- Atomic Number vs Atomic Mass
Moseleyn rearranged the order of the elements from increasing atomic mass to increasing atomic number. -
Glenn T. Seaborg- The Actinides
Seaborg moved 14 elements from the ain body of the Periodic Table to below the Lanthanide series. This series is now known as the Actinides series