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Chemistry of Argon (Z=18)

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  • Argon is it is colorless, tasteless and odorless noble gas that is located in Group 18 on the Periodic Table. It was discovered by Henry Cavendish in 1785 and was named Argon, which is derived from the Greek word "argos" meaning inactive. Cavendish formed oxides of nitrogen by passing electric currents through air, then dissolved them in water to get nitric acid, but was unable to get all of the air to react. He suspected that there was a then unidentified gas component of air; Ramsay and Rayleigh went on to isolate this component in 1894, and the new found element was thus named Argon.

    Periodic Trend Facts

    Since it is a part of the noble gas family, argon has a complete octet in its valence electron shell. It is the third element of Group 18 of the Periodic Table, and has an atomic number of 18. According to periodic trends, argon has a very low melting point and weak intermolecular forces, which affects its ability to form molecules. Argon also has the lowest melting point in its period, which is 84 K. Its electron configuration is 1s2 2s2p6 3s2p6.

    graphic of Argon's shell model


    Argon is very abundant in the atmosphere, which is 0.943% Ar by volume. It is also found in the photosphere: scientists are able to measure solar argon abundance by looking at the amount found in solar flares, lunar soil, solar wind, and samples from Jupiter's atmosphere.

    Formation of Molecules

    Due to its full valence electron shell and weak intermolecular forces, it is very difficult for argon to form molecules. For this reason it is usually considered one of the most inert noble gases. It is only recently that scientist have been able to form molecules using argon, the most notable of which is \(HArF\). This was accomplished by mixing argon with ultraviolet light and hydrogen fluoride. It is predicted that there are more molecules that we may be able to create soon as well, such as \(HArCl\).


    For years argon has been used in ordinary incandescent light bulbs to replace the oxygen that would otherwise shorten the lifetime of the filament. It is used in some types of welding where active atmospheric gases would interfere with the process. Argon is also used in various types of "black lights" or UV lamps since excitation of the gas produces a significant amount of ultraviolet radiation. A few curious compounds have been made with argon but they are not very stable.

    Because of argon's inertness, it is very useful in commercial settings. For example, it can be used in the formation of semiconductor materials and in metallurgical processes. Argon is also useful in welding, as it can protect substances from the corrosive properties of oxygen and nitrogen.


    1. What is the electron configuration of argon?
    2. Name 2 commercial uses for argon.
    3. Why is argon considered to be chemically inert under most circumstances?
    4. What is the freezing point of argon?
    5. What is one of the molecules created using argon?


    1. 1s2 2s2p6 3s2p6
    2. Welding, electric lightbulbs, semiconductor materials, metallurgical processes.
    3. Argon has a full valence electron shell, and has weak intermolecular forces.
    4. -189.2 C.
    5. HArF


    1. Cohen,Arik. Lundell, Jan. Gerber, R. Benny. First compounds with argon–carbon and argon–silicon chemical bonds. The Journal of Chemical Physics, Vol. 119, No. 13, pp. 6415–6417, 1 October 2003
    2. Lodders, Katharina. The Solar Argon Abundance. Astrophysical Journal, May 2007.
    3. Petrucci, Ralph. Harwood, William. Herring, Geoffrey. Madura, Jeffery. GENERAL CHEMISTRY Principles and Modern Applications 9th Edition. Macmillan Publishing co, New


    • Katherine Cubbon (UCD)

    Stephen R. Marsden (ChemTopics)