Argon is a rare and inert gas and belong to the Nobel gases. It was discovered by Sir William Ramsay and Lord Rayleigh in 1894. It emits unique and sharp spectral lines and is widely used in high speed photography and lasers.
History and Discovery
Argon was discovered by Sir William Ramsay and Morris Travers in 1898, as a residual gas in a chamber after all components of liquid air, including nitrogen, carbon dioxide and oxygen have been removed. Ramsay received the Nobel prize in Chemistry in 1904 for his contributions in the discovery of argon and other noble gases, except radon. Before its discovery, Ramsay believed that in nature, often element hides in another. And the gap between the discovered elements in the periodic table made him look closely within elements. The name argon has been derived from the Greek word, ἀργόν, that means lazy as it is inactive and does not react with other elements . The symbol of argon is Ar .
|Periodic Table Classification||Group 18
|State at 20C||Gas|
|Color||Colorless gas exhibiting a lilac/violet glow when placed in an electric field|
|Electron Configuration||[Ne] 3s2 3p6|
|Electron Shell||2, 8, 8|
|Density||1.78 g.cm-3 at 20°C|
|Atomic Mass||39.95 g.mol -1|
|Electronegativity according to Pauling||n/a|
Argon is an abundant element and is ranked as the third most abundant gas that is present in the atmosphere of Earth. Argon is the most abundant gas among the noble elements and is 500 times more abundant than neon. It is present in about 0.00015% (1.288 % by mass) of the Earth’s crust. of liquid air. The argon in earth’s atmosphere is argon-40 and is radiogenic as it is produced during the decay cycle of potassium-40 that is present in the earth’s crust. Argon is also found in abundance in space. Argon-36 is the most abundant isotope of argon and is produced in supernova in the process of stellar nucleosynthesis. Argon is present in the sea water in a concentration of 0.45ppm . Argon is produced by fractional distillation of liquid air .
Argon is colorless and odorless gas. Argon in solid state is white and have a face-centered cubical structure. Argon has a density of 1.784 g/L at standard conditions. Argon is affected by an external magnetic field and is diamagnetic. Argon is water soluble. It is non-flammable and has very low thermal conductivity. The boiling point of argon is −185.848 °C and melting point is −189.34 °C.
Argon is chemically inactive. Its outer most shell has eight electrons, a complete octet, which renders the element inactive and do not bond with other elements at room temperature. However, under extreme conditions, it reacts with hydrogen and fluorine and forms argon fluorohydride (HArF) that is stable at -256 °C. It is a crystalline white solid and is stable at low temperature. Crystals of hydride can be formed under increased pressure, i.e. above 5GPa. Argon has an oxidation state of zero .
Significance and Uses
- Argon is widely used in welding process as the shielding gas. It is used in graphite electric furnace in order to prevent the burning of graphite.
- Argon is used for making incandescent fluorescent lamps.
- Argon is also used to make lasers and fluorescent glowing equipment.
- Argon-krypton dating is used to determine the age of rocks by analyzing the emission pattern of these elements.
- Argon is used as a cheap alternative to nitrogen in various applications.
- Argon is widely used in research areas, including dark matter sciences and neutrino experiments.
- Argon is used to increase the shelf life of various food products.
- Argon is used in medical field to destroy cancer cells (cryoablation) and electrosurgery.
Argon is non-toxic in nature in all its forms, solid, liquid or gas .
Isotopes of Argon
There are seven known isotopes of argon and three are main isotopes that are present on the Earth: argon-38, argon-36 and argon-40. The most stable isotope is argon-40 and has a half-life of around 1.25×109 years.
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