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John Dalton
Chemists hadn’t yet fully grasped the nature of atoms, as described in the atomic theory proposed by English schoolteacher John Dalton -
1860
Atomic weights had been well enough understood and measured for deeper insights to emerge -
John Newlands
Noticed that arranging the known elements in order of increasing atomic weight produced a recurrence of chemical properties every eighth element -
Bohr
Bohr’s table added elements discovered -1869
Created his own version of the table- 1922 -
Dmitri Mendeleev
he published his firts timeline, this arrangement placed elements with similar properties into horizontal rows. -
Mendeleev
His realized that some groups of similar elements showed a regular increase in atomic weights; other elements with roughly equal atomic weights shared common properties. Mendeleev’s table did more than foretell the existence of new elements. It validated the then-controversial belief in the reality of atoms. -
1869
Mendeleev realized that the physical and chemical properties of elements were related to their atomic mass in a 'periodic' way, and arranged them so that groups of elements with similar properties fell into vertical columns in his table. -
Johannes Wislicenus
Declared that the periodicity of the elements’ properties when arranged by weight indicated that atoms are composed of regular arrangements of smaller particles -
Mendeleev
Chemists widely recognized his law as a landmark in chemical knowledge -
1907
Mendeleev’s death
