Argon Mass Number

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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 [1]. The symbol of argon is Ar [2].

Argon is a chemical element with the 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 abundant gas in the Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as carbon dioxide (400 ppmv), and more than 500 times.

Argon Mass Number
  • 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 1.25×10 9 years.
  • Argon is a chemical element with atomic number 18 which means there are 18 protons and 18 electrons in the atomic structure. The chemical symbol for Argon is Ar. Argon is the third-most abundant gas in the Earth’s atmosphere, at 0.934% (9340 ppmv). It is more than twice as abundant as water vapor (which averages about 4000 ppmv, but varies greatly), 23 times as abundant as.
Argon Mass Number

Argon

Periodic Table ClassificationGroup 18
Period 3
State at 20CGas
ColorColorless gas exhibiting a lilac/violet glow when placed in an electric field
Electron Configuration[Ne] 3s2 3p6
Electron Number18
Proton Number18
Electron Shell2, 8, 8
Density1.78 g.cm-3 at 20°C
Atomic number18
Atomic Mass39.95 g.mol -1
Electronegativity according to Paulingn/a

Occurrence

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 [2]. Argon is produced by fractional distillation of liquid air [3].

Physical Characteristics

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.

Chemical Characteristics

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 [4].

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.

Health Effects

Argon is non-toxic in nature in all its forms, solid, liquid or gas [4].

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.

REFERENCES

[1]. William Ramsay; Morris W. Travers (1898). “On a New Constituent of Atmospheric Air”. Proceedings of the Royal Society of London. 63 (1): 405–408. doi:10.1098/rspl.1898.0051.

[2]. Emsley, J. (2001). Nature’s Building Blocks. Oxford University Press. pp. 44–45. ISBN978-0-19-960563-7.

[3].“Argon, Ar”. Etacude.com. Archived from the original on 7 October 2008. Retrieved 8 March 2007

[4].Material Safety Data Sheet Gaseous Argon, Universal Industrial Gases, Inc. Retrieved 14 October 2013

Number

[5]. Kleppe, Annette K.; Amboage, Mónica; Jephcoat, Andrew P. (2014). “New high-pressure van der Waals compound Kr(H2)4 discovered in the krypton-hydrogen binary system”. Scientific Reports. 4. Bibcode:2014NatSR…4E4989K. doi:10.1038/srep04989.

Argon Mass Number

Argon Atomic Mass Number

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