PRESENTATION OUTLINE
History:
Polish chemist Kasimir Fajans and German chemist Oswald Göhring discovered protactinium in 1913 at Karsrule, Germany. Protactinium's existence was confirmed in 1918 when another isotope, protactinium-231, was independently discovered and studied by two groups of scientists, Otto Hahn and Lise Meitner of Germany and Frederick Soddy and John Cranston of Great Britain. Protactinium was first isolated by Aristid V. Grosse in 1934. The element name comes from a combination of the Greek word ‘protos’ meaning first and ‘actinium.’
Significance:
A measurement of the ratio of Pa and Th in ocean
sediments allows scientists to reconstruct the movements of bodies of
North Atlanticwater that took place during the melting of the last ice-age. Protactinium is used mainly for research purposes.
Products:
The primary decay products of 231Pa and isotopes of Pa lighter than (and including 227Pa) are isotopes of actinium and the primary decay products for the heavier isotopes of Pa are isotopes of uranium.
History:
Scandium was discovered by Lars Fredrik Nilson, a Swedish chemist, in 1879 while attempting to produce a sample of pure ytterbia from 10 kilograms of the mineral euxenite. Metallic scandium was first produced in 1937 and the first pound (0.45 kilograms) of pure scandium was produced in 1960. Scandium is a soft, light metal that might have applications in the aerospace industry.
Significance:
Scientists have only studied a few compounds of scandium. About 20 kilograms (44 pounds) of scandium oxide (Sc2O3), also known as scandia, are used each year in the United States in the production of high intensity lights. Scandium iodide (ScI3) is added to mercury vapor lamps so that they will emit light that closely resembles sunlight.
Particularly promising is the strengthening of aluminium alloys with as little as 0.5% scandium.
Products:
Alloys of scandium and aluminum are used in some kinds of athletic equipment, such as aluminum baseball bats, bicycle frames and lacrosse sticks. It is expected that scandium-aluminum alloys will be important in the manufacture of fuel cells.
History:
Krypton was discovered on May 30, 1898 by Sir William Ramsay, a Scottish chemist, and Morris M. Travers, an English chemist, while studying liquefied air. Small amounts of liquid krypton remained behind after the more volatile components of liquid air had boiled away. The earth's atmosphere is about 0.0001% krypton.
Significance:
Krypton-83 has application in magnetic resonance imaging (MRI) for imaging airways. In particular, it may be used to distinguish between hydrophobic and hydrophilic surfaces containing an airway.
Krypton has an important role in production and usage of the krypton fluoride laser.The laser has high beam uniformity, short wavelength, and the ability to modify the spot size to track an imploding pellet.
Products:
Krypton is used in some types of photographic flashes used in high speed photography. Some fluorescent light bulbs are filled with a mixture of krypton and argon gases. Krypton gas is also combined with other gases to make luminous signs that glow with a greenish-yellow light.
History:
Argon was discovered by Sir William Ramsay, a Scottish chemist, and Lord Rayleigh, an English chemist, in 1894. Argon makes up 0.93% of the earth's atmosphere, making it the third most abundant gas. Argon is obtained from the air as a byproduct of the production of oxygen and nitrogen.
Significance:
Argon is frequently used when an inert atmosphere is needed. It is used to fill incandescent and fluorescent light bulbs to prevent oxygen from corroding the hot filament. It is used in potassium-argon dating to determine the age of rocks.
Products:
Argon is also used to form inert atmospheres for arc welding, growing semiconductor crystals and processes that require shielding from other atmospheric gases.
History:
Tungsten was discovered by Juan José and Fausto Elhuyar, Spanish chemists and brothers, in 1783 in samples of the mineral wolframite. Today, tungsten is primarily obtained from wolframite and scheelite (CaWO4) using the same basic method developed by José and Elhuyar. Tungsten ores are crushed, cleaned and treated with alkalis to form tungsten trioxide (WO3).
Significance:
X-ray tubes for medical use have a tungsten emitter coil and the screen used to view X-rays rely on calcium and magnesiumtungstate phosphors to convert X-rays into blue visible light. Tungsten is also used in microchip tecnology and liquid crystals displays.
Products:
Tungsten is used in filaments in incandescent light bulbs, it is also used in electric contacts and arc-welding electrodes. Tungsten is used in alloys, such as steel, to which it imparts great strength. It is also used to make beautiful rings.
