Thursday, February 21, 2008

The Elements

For those of you just joining us, I've been posting short summaries on each of the elements in the Periodic Table. These are types of atoms, the most basic building blocks from which our entire Universe is made.
Tonight we cover three metals. Metals, as a group, are good conductors of heat and electricity. They are also usually easy to shape by melting and cooling, and become shiny when you polish them. 

The great utility of metals for structural and manufacturing purposes arises from their strength, that is, their resistance to breaking when stressed. Metals have also been used throughout history for fine and decorative art.

Consider the following...

Manganese:
Atomic Symbol: Mn
Atomic Number: 25
Manganese was known long before it was isolated as an element. Its common minerals were used by glassmakers to remove the greenish tint of natural glass which is due to traces of iron in the sand from which it is made. It was first distinguished as an element in 1774 by the Swedish chemist Karl Wilhelm Scheele. The metal does not occur in the free state, except in meteors, but is widely distributed over the world in the form of ores.
It is an essential element for all species. For some creatures, such as the red ant, it makes up a significant portion of their weight. Humans also need manganese, although this was only realized in the 1950s, perhaps because the requirement is so modest. It is still not clear exactly for what part of our metabolism it is essential.
The most surprising occurrence of manganese is on the ocean floor, where there is an estimated trillion tons of manganese-rich nodules scattered over large areas.

Iron:
Atomic Symbol: Fe
Atomic Number: 26
The ancient Hittie empire of Asia Minor appears to have been the first to discover how to extract iron from its ores, beginning around 1500 BC. The Iron Age had begun, characterized by heavier and stronger weapons. These weapons dominated warfare for more than 2000 years.
The Greek philosopher Thales discovered, in 585 BC, that pieces of iron ore that came from Magnesia in Lydia had the strange power to attract iron filings. They were called magnets, after the place from which they came.
In addition to being a key part of hemoglobin, iron also plays a key role in the synthesis of DNA. There are also regions of the brain that are rich in iron.
Iron is in fact the Earth's most abundant element because the 7000 kilometer diameter core consists mostly of the molten metal. In effect, our planet is a large iron sphere.

Cobalt:
Atomic Symbol: Co
Atomic Number: 27
Cobalt is a relatively weak metal and a poorer conductor, except at very high temperatures, at which it becomes an outstanding conductor.
This metal is used in alloys to make magnets, and in ceramics and paints to give a blue color. Certain types of stainless steel contain it, including that which is used to make razor blades.
All animal life requires a supply of cobalt in the diet, usually as the central atom in the vitamin B12.
Cobalt was once popular for making "sympathetic ink", now known as invisible ink. This strange liquid remains unseen until it is warmed, which makes it turns dark blue. Exactly who first came across this phenomenon is unknown, but it was used in espionage through the seventeenth century.

My posts on the previous elements are available here.

An exceptional book of reference on the subject is Nature's Building Blocks: An A-Z Guide to the Elements, by John Emsley. This and other fine volumes available through the Hansisgreat Store.

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