Saturday, July 5, 2008

The Elements

For those of you who are new to Hansisgreat, I have a continuing series on the Periodic Table of Elements. From the widely known to the relatively obscure, here are a few facts about the atoms that compose our entire material world.

Modern Periodic Tables are divided into groups (vertical columns, atoms with the same number of electrons in the outer shell), and periods (horizontal rows, including atoms with the same number of shells). Today's elements are the first in the fifth period, atoms with five levels of electrons.
All three of these elements were discovered in modern times, and remain mostly obscure because they have few industrial uses and no biological roles to play. Strontium was included in an early Periodic Chart developed by John Dalton in 1804 (see above right). The other two were known for years before they were actually discovered in the natural world.

Atomic Symbol: Rb
Atomic Number: 37
Rubidium is a soft, silvery metal that rusts so quickly from contact with water vapor in the air that it has to be stored in oil or grease. Contact with heat produces the brilliant purple flame seen left.
Little rubidium is produced commercially, because what it can do is done equally well by sodium, which is 5000 times cheaper; or even potassium, 300 times cheaper. Rubidium costs about $20,000/Kg, making it more expensive than gold or platinum. It is used for research purposes only. Its most notable use was that it was cooled to just a few billionths of a degree above absolute zero, verifying that 
-273.15oC is the coldest temperature any material can have.

Atomic Symbol: Sr
Atomic Number: 38
This element quickly disappears from the body, with less than 0.3% of a dose remaining after one day. For this reason, it is often used in medical research. It is best known for the brilliant reds it produces when burned in fireworks or highway flares.
Although Strontium-90 is a dangerous radioactive isotope, it is a useful by-product of nuclear reactors used in television screens, space vehicles, and remote weather stations. It caused major worldwide pollution when it was released into the environment during nuclear weapons testing between 1945 and 1963. Its presence was detected in the bodies of newborn infants, showing how prevalent it had become.

Atomic Symbol: Y
Atomic Number: 39
Pronounced it-ree-uhm, it is named after Ytterby, Sweden. Three new elements (yttrium, terbium, and erbium) were all discovered in the ore mined from this famous Swedish town.
Radioactive Yttrium-90 has been used in several types of medical research, generally for cancer (because it attaches itself to cancer cells).
Samples of material from the Moon, brought back from the six Apollo missions between 1969 and 1972, were found to have relatively high yttrium contents.

For my posts on the previous elements, numbered 1-36, are available here.

If you're interested in a terrific reference book on the Periodic Table, check out Nature's Building Blocks, by John Emsley.

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