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Ashraf Abu Izam
Grade 10 - B
Latin Patriarchate High School
T. Lina Qura
Argon is a chemical element with symbol Ar and atomic number 18. It is in group 18 of the
periodic table and is a noble gas. Argon is the third most common gas in the Earth's
atmosphere, at 0.93% (9,300 ppm), making it approximately 23.8 times as abundant as the next
most common atmospheric gas, carbon dioxide (390 ppm), and more than 500 times as
abundant as the next most common noble gas, neon (18 ppm). Nearly all of this argon is
radiogenic argon-40 derived from the decay of potassium-40 in the Earth's crust. In the
universe, argon-36 is by far the most common argon isotope, being the preferred argon isotope
produced by stellar nucleosynthesis in supernovas.
The name "argon" is derived from the Greek word αργον, neuter singular form of αργος
meaning "lazy" or "inactive", as a reference to the fact that the element undergoes almost no
chemical reactions. The complete octet (eight electrons) in the outer atomic shell makes argon
stable and resistant to bonding with other elements. Its triple point temperature of 83.8058 K is
a defining fixed point in the International Temperature Scale of 1990.
Argon is produced industrially by the fractional distillation of liquid air. Argon is mostly used
as an inert shielding gas in welding and other high-temperature industrial processes where
ordinarily non-reactive substances become reactive; for example, an argon atmosphere is used
in graphiteelectric furnaces to prevent the graphite from burning. Argon gas also has uses in
incandescent and fluorescent lighting, and other types of gas discharge tubes. Argon makes a
distinctive blue-green gas laser.
Argon has approximately the same solubility in water as oxygen, and is 2.5 times more soluble
in water thannitrogen. Argon is colorless, odorless, nonflammable and nontoxic as a solid,
liquid, and gas. Argon is chemically inert under most conditions and forms no confirmed stable
compounds at room temperature.
Although argon is a noble gas, it has been found to have the capability of forming some
compounds. For example, the creation of argon fluorohydride (HArF), a marginally stable
compound of argon with fluorine and hydrogen, was reported by researchers at the University
of Helsinki in 2000. Although the neutral ground-state chemical compounds of argon are
presently limited to HArF, argon can form clathrates with water when atoms of it are trapped in
a lattice of the water molecules. Argon-containing ions and excited state complexes, such as
ArH+and ArF, respectively, are known to exist. Theoretical calculations have predicted several
argon compounds that should be stable, but for which no synthesis routes are currently known.
Argon's complete octet of electrons indicates full s and p subshells. This full outer energy level
makes argon very stable and extremely resistant to bonding with other elements. Before 1962,
argon and the other noble gases were considered to be chemically inert and unable to form
compounds; however, compounds of the heavier noble gases have since been synthesized. In
August 2000, the first argon compound was formed by researchers at the University of
Helsinki. By shining ultraviolet light onto frozen argon containing a small amount of hydrogen
fluoride with caesium iodide, argon fluorohydride (HArF) was formed. It is stable up to 40
kelvin (−233 C).
Argon is used in industrial processes which involve high-temperature. It has various uses such
as in graphite electric furnaces to prevent the graphite from burning, metal inert gas welding for
example tungsten and in the processing of titanium and other reactive elements. It is also used
to grow crystals of germanium and silicon. Though it can cause headache, dizziness, dullness
and suffocation if inhaled. It can cause frostbite if it comes into contact with liquid.
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