PERIOD OF THE PERIODICAL TABLE

ANTOINE LAVOISIER

• Wrote the first book about the elements
• Included light and caloric to the list of elements
• Classified elements to be either a metal or non-mental.

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• Grouped the elements into three
• Called these three groups the "Triad"

ALEXANDRE Chancourtois

• noticed the periodicity of the elements
• Devised the early form of the periodic table

JOHN NEWLANDS

• Classified the elements into eleven groups
• Noted that there are many pairs of similar elements

HENRY MOSELEY

• Discovered the relationship between x-ray wavelength and atomic number
• Resequenced the elements by nuclear charge
• Discovered gaps in the periodic table

DIMITRI MENDELEEV

• Arranged the elements by atomic mass
• Left spaces for future discoveries