Monday, April 21, 2008

The Elements

The first two elements I'm posting on tonight are quite obscure; in fact, most people have never even heard of them! Strangely enough, their existence was known years before they were actually discovered.
When organizing the first Periodic Table, Dmitri Mendeleyev recognized that there must be elements below aluminum and silicon, and was even able to describe some of their properties. The discovery of gallium and germanium confirmed his theories, and proved that science had indeed developed an accurate method for organizing the chemicals that make up our world.

Atomic Symbol: Ga
Atomic Number: 31
The name is derived from Gallia, the latin name for France, this element's country of origin. It was discovered in 1875 by Paul-Emile Lecoq de Boisbaudran in a zinc-ore from the Pyrenees. Several ores, such as the aluminum ore bauxite, contain significant amounts of gallium, and coal often has a high gallium content.
Gallium is much more abundant than lead, but less accessible because it is not concentrated in any particular mineral deposits: it is widely dispersed. It will actually melt when held in your hand, and remains liquid at a wider temperature range (2373oC) than any other known substance. For this reason, it has often been used in high temperature thermometers.

Atomic Symbol: Ge
Atomic Number: 32
In September 1885, a miner working 400 meters underground near Freiberg, Germany produced a mysterious silver ore. After months of analysis, Clemens A. Winkler discovered that 7% of the sample was a previously unknown element, which he named germanium after his home country.
Germanium is a superconductor, and was the first metal to be used in transistors beginning in 1942. Since all known sources of the metal were in Germany, the US government developed a discrete process for removing it from industrial waste. By 1948, this system was perfected and transistor radios went on sale to the public.

Atomic Symbol: As
Atomic Number: 33
Human contact with arsenic goes back to prehistoric times. The hair of an "Iceman" preserved in a glacier in the Italian Alps contains high levels of the element, probably as a by-product from the smelting of copper.
Arsenic gained notoriety during the nineteenth century as an undetectable poison, used frequently for removing unwanted dukes, kings, and even popes. It was readily available as weed-killer, and could be extracted from fly-paper. Even large doses can now be treated, if diagnosed in time.
A much more widespread threat from arsenic exists today in many developing countries, where polluted streams have exposed over 70 million people to chronic arsenic poisoning over many years. The World Health Organization's recommended maximum level of arsenic in drinking water is 0.01 milligrams per liter. Wells in Thailand, India, and Bangladesh may contain as much as 4.0 milligrams per liter.

My posts on all the previous elements, from hydrogen to zinc are here.

There's a good reference book on the periodic table called Nature's Building Blocks, by John Emsley.

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