History Of Periodic Table

Question 1

Mendeleev

Answer 1

Gaps were left when elements did not fit property pattern.
Properties of missing elements were predicted.
Periodicity of properties.
Atomic weight determines character of element.

Question 2

Henry Moseley

Answer 2

Determined atomic number for each element.

Modified table - order of atomic number not atomic weight.

Question 3

John Newlands

Answer 3

Devised first periodic table in order of relative atomic weights. Showed electrons in 7 octaves. Periods went down the table.