PERIODIC TABLE CHEMICAL INFO

[AH]

Periodic Chart info:
http://www.radiochemistry.org/periodictable/list1.html
http://chemlab.pc.maricopa.edu/periodic/about.html
http://chemlab.pc.maricopa.edu/periodic ... tml#search
A short history of the periodic table.

The rectangular periodic table is familiar to anybody who has ever been in a
science laboratory or classroom. This ingenious functional groupingof the
chemical elements was created by several European scientists in the decade
of the 1860's. In 1863, a 44 year old French geologist, A. E. Béguyer de
Chancourtois created a list of the elements arranged by increasing atomic
weight. The list was wrapped around a cylinder so that several sets of
similar elements lined up, creating the first geometric representation of
the periodic law.

In England, 32 year old analytical chemist John A. R. Newlands was also
wrapping the elements, noting that chemical groups repeated every eight
elements. He named this the octave rule, and compared it to a musical scale.
Some less observant members of the English Chemical Society considered this
absurd, so his work was ignored for years.

Chemists Dmitrii I. Mendeleev, a Russian, and German Lothar Meyer were
working independently in 1868 and 1869 on the arrangement of elements into
seven columns, corresponding to various chemical and physical properties.
Their tables were similar - they acknowledged each other's work - the
differences are subtle but important: Meyer's table was an accurate (for the
time) accounting of the known facts about each element, such as melting
point and atomic volume. The table clearly showed the existence of periodic
chemical families. In 1870 Meyer's table and description of the periodic law
was published in Liebig's Annalen.

A year earlier however, the 35 year old Mendeleev presented a much bolder
and scientifically useful table. His paper, On the Relation of the
Properties to the Atomic Weights of the Elements, was enthusiastically
received by the Russian Chemical Society. In it, the periodic relationship
between chemical groups, that is, elements with a similar stoichiometry of
reaction, is clearly illustrated. In a scientific triumph, gaps in the table
accurately predicted undiscovered elements.

Although it is nearly 130 years old, Mendeleev's table differs little from
the charts on the walls of laboratories today. The insight obtained in that
productive decade resulted in a tool that furthers understanding and eases
the use of chemistry in every laboratory in the world.