He obtained this from the University of California when he visited their cyclotron laboratory in 1936 and where this metal had been exposed to various high energy particles. Technetium only came to light in 1937 when Emilio Segr? at the University of Palermo in Sicily separated it from a sample of molybdenum. Those who claimed to have discovered it and gave it names like davyum, lucium, and nipponium, were mistaken. Technetium occupies the place below manganese in the periodic table, and it long tantalised chemists because it could not be found. This proved conclusively that stars were the furnaces where the chemical elements are manufactured. Since all isotopes of technetium are relatively short lived compared to the age of stars, and especially red giants which are at the end of their lives, it could only mean that this element was continuously being formed within the star itself. In 1952, Paul Merrill, an astronomer at the Mount Wilson and Palomar Observatories in California examined the light given off by such stars, and it clearly showed technetium was present in abundance. Nevertheless, technetium has turned up in some most unlikely places in the universe, namely red giant stars. However, this was not long enough for the technetium, which was present when the Earth was formed 4.57 billion years ago, to have survived to the present day. The longest lived technetium isotope is technetium-98 with a half-life of 4.2 million years. When it is accompanied by a diphosphate ion it binds strongly to the heart muscle and this can be used to assess the damage done by a heart attack. When a colloidal suspension of technetium-99m and tin is injected into the body it binds to red blood cells and so can be used to map malfunctions of the circulatory system. Technetium-99m is not used only in cancer treatments. The method is especially useful in highlighting cancers in the intestines, kidneys, brain, and bones. ![]() By mapping the gamma-ray emissions, it is possible to diagnose the affected sites. (Technetium-99 itself has a half-life of 211 000 years.) The medical diagnostic technique is known as immunoscintigraphy which involves its being incorporated into a monoclonal antibody that binds to cancer cells. Technetium-99m has a half-life of six hours and emits only gamma-rays as this isotope isomer reverts to technetium-99. Today other countries like Holland, South Africa, and Argentina are also producing it. Because molybdenum-99 has a half-life of only 67 hours there was a real risk that global demand for technetium would not be met. Technetium-99m was mainly made at a plant at Chalk River, Ontario, Canada, but this unexpectedly ceased production in 2009 as a result of a power blackout which affected production for several weeks. (It poses no long term threat to those being treated because technetium is quickly eliminated from the body.) The isotope used is technetium-99m and this is produced from molybdenum-99, which itself is made by bombarding uranium-235 with neutrons. It is injected into tens of millions of people every year to diagnose difficult-to-detect cancers. ![]() Here the brain activity is colour-coded, from red (most active) through yellow to green and blue (least active).ĭespite all its isotopes being radioactive, this element is used around the world to save lives.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |