Periodic Table Physical Properties Students will understand the development of the periodic table as a function of properties of the elements.

Discovery of Elements - Until 1828 Up to 1200 a.d., only 11 elements were known… 6 new elements found from 1200-1700 a.d. 19 each from 1700-1800 and 1800-1828 New total: 53 Elements Discovered 3 2 1 19 11 9 BC AD 100 1200 1500 1600 1700 1800 1828

53 known elements in 1828 How many ways can these be organized? Cu Fe Pb Ag S As Sn H Ni Sb Bi Pt Cl Co Zn Hg Al Si W 53 known elements in 1828 How many ways can these be organized? Os Ir Nb Se Te Br U Mn I Na F Ce Au Zr Y Cr Cd P Li B Mo Sr Ti Ba Rb K O Mg Ca Ta Be Pd N

In 1828, Johann Wolfgang Dobereiner developed triads Li Na K These are groups of three elements containing similar traits with the atomic weight of the middle element the average of the other two. S Se Te Ca 40 Sr 87 Ba 137 (3 + 19) / 2 = 11 = Na (40 + 137) / 2 = 87 = Sr (16 + 52) / 2 = 34 = Se

The Law of Octaves “The eighth element, starting from the given one, is a kind of repetition of the first, like the eighth note of an octave of music.” -- John Newlands

1869- The Periodic Law The physical and chemical properties of the elements are periodic functions of their atomic weights. Introduced by Dmitri Mendeleev - “father of the periodic table” Arrange by atomic mass

Mendeleev’s Periodic Table (original publication)

Mendeleev predicted the existence and properties of several elements unknown at his time. He was wicked smart. Mendeleev's Predictions about Eka-Aluminum: Atomic weight: about 68 69.7 Boiling Point: low 30° C Density: 5.9 5.94 Formula of Oxide: EkaAl2O3 Ga2O3 Formula of chloride: EkaAlCl3 GaCl3 Chemistry of hydroxide: EkaAl(OH)3 Ga(OH)3

Henry Moseley … developed the idea of atomic numbers to arrange the elements. This solved the riddle of the discrepancies in Mendeleev’s Periodic table.

Modern Version of the Periodic Law The properties of the elements are periodic functions of their atomic numbers. There are 18 groups or families in the periodic table H Li Na K Rb Cs Fr He Ne Ar Kr Xe Rn Be Mg Ca Sr Ba Ra B Al Ga In Tl C Si Ge Sn Pb

There are 7 periods in the periodic table ------->

The periodic table is an ordered logical arrangement of the chemical elements into groups with similar properties.

From the 19th Century Physicist’s Stowe Table Benfrey’s Table