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Chemists hadn’t yet fully grasped the nature of atoms, as described in the atomic theory proposed by English schoolteacher John Dalton

Atomic weights had been well enough understood and measured for deeper insights to emerge

Noticed that arranging the known elements in order of increasing atomic weight produced a recurrence of chemical properties every eighth element

Bohr’s table added elements discovered -1869
Reated his own version of the table- 1922

he published his firts timeline, this arrangement placed elements with similar properties into horizontal rows.

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.

Declared that the periodicity of the elements’ properties when arranged by weight indicated that atoms are composed of regular arrangements of smaller particles

Chemists widely recognized his law as a landmark in chemical knowledge

Mendeleev’s death