The History of the Periodic Table Chapter 6

J.W. Dobereiner In work beginning in 1817, Döbereiner discovered trends in certain properties of selected groups of elements. For example, the average atomic mass of lithium and potassium was close to the atomic mass of sodium. A similar pattern was found with calcium, strontium, and barium, These sets of elements became known as Döbereiner's triads.

John Newlands An English scientist called John Newlands proposed his Law of Octaves in 1864. Classified the 56 established elements into 11 groups based on similar physical properties. This law stated that any given element will exhibit analogous behavior to the eighth element following it in the table. He arranged all the elements known at the time into a table in order of relative atomic mass.

Dmitri Mendeleev In 1869, a Russian chemist called Dmitri Mendeleev published a periodic table. Mendeleev also arranged the elements known at the time in order of relative atomic mass. Mendeleev predicted the existence of elements not yet discovered using the periodic properties of the known elements.

Mendeleev’s Periodic Table

Henry Moseley Used atomic number as the organizing principle for the periods. Modern Periodic Law: When elements are arranged by increasing atomic number, there is a periodic repetition of their chemical and physical properties.

Glenn Seaborg Into the 1930s the heaviest elements were being put up in the body of the periodic table.(d block) Glenn Seaborg removed them and placed them in the f-block of the periodic table He named them the Actinide series.

The Modern Periodic Table

Group Names Group 1 (IA, 1A): the alkali metals Group 2 (IIA, 2A): the alkaline earth metals Group 13 (IIIA, 3A): the boron family Group 14 (IVA, 4A): the carbon family Group 15 (VA, 5A): nitrogen family Group 16 (VIA, 6A): oxygen family Group 17 (VIIA, 7A): the halogens Group 18 (VIIIA, 8A): these are the noble gases These groups of elements are also known as representative elements

Location of metals, nonmetals and metalloids Metals are found to the left of the zig zag line Good conductors of heat and electricity Malleable and ductile Nonmetals are found to the right of the zig zag line Poor conductors of heat and electricity Brittle Metalloids are found ON the zig zag line. Possess the properties of both metals and nonmetals.

Location of metals, nonmetals and metalloids

Transition and Inner Transition Metals Transition Metals: These metals are found in the d block of the periodic table. These are multivalent (can form more than one charge) Examples: Cu, Ag, Fe, Au Inner Transition Metals: These metals are found in the f block of the periodic table. Examples: U, Th, Pa