History of the Periodic Table Chapter 6

Objectives: Discuss the contributions of Dobereiner, Newlands, Meyer, Mendeleev, and Moseley to the classification of the elements. Discuss the significance of Mendeleev’s work and how it relates to the modern periodic table.

Dobereiner First person to create reasonably accurate measurements for atomic mass.

Newlands In 1864, Newlands proposed an organization scheme for the elements By arranging them in order of increasing atomic mass, he realized that their properties repeated every eighth element. He called this periodicity the Law of Octaves. Acceptance of his arrangement wasn’t immediate because it didn’t work universally in predicting chemical properties.

Meyer & Mendeleev In 1869, Lothar Meyer demonstrated a connection between atomic mass and elemental properties. In 1869, a Russian chemist named Dimitri Mendeleev also came up with a way of organizing the elements that were known at the time. Both chemists set the elements out in order of atomic mass Both then grouped them into rows and columns based on their chemical and physical properties. Mendeleev predicted the existence and properties of undiscovered elements, which is largely why his table got such wide acceptance.

Mendeleev’s Early Periodic Table, Published in 1872

Moseley Instead of ordering elements by total atomic mass, order by proton (atomic) number. This creates some minor shufflings in Mendeleev’s table and allows us to better predict unknown elements.