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12.8: Group VIIIA: Noble Gases

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    49516
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    The properties of the noble gases are summarized in the table below. The noble gases have a complete octet of electrons ns2np6 or just ns2 for helium, leaving them with little chemical reactivity. Sure enough,the ionization energies of He and Ne are greater than 2000 kJ mol–1, and it is unlikely that these noble gases will ever be induced to form chemical bonds. The same probably applies to Ar. Kr and especially Xe do form compounds though, which was discussed in the halogens section, and Rn might be expected to be even more reactive. Rn is radioactive, however, and study of its chemistry is difficult.

    Table \(\PageIndex{1}\) Properties of the Group VIII Elements.

    Element Symbol

    Electron

    Configuration

    Usual

    Oxidation State

    Radius/pm - Covalent

     

    Helium He 1s2 0

    ...

     

    Neon Ne [He]2s22p6 0

    ...

     

    Argon Ar [Ne]3s23p6 0

    ...

     

    Krypton Kr [Ar]4s23d104p6 +2

    110

     

    Xenon Xe [Kr]5s24d105p6 +8, +6, +4, +2 130

     

     

    Symbol Ionization Energy/MJ mol–1

    Density/

    g cm–3

    Electro-

    negativity

    Melting

    Point (in °C)

      First Second      
    He 2.379 5.257 0.179 ...

    -272

     

    Ne 2.087 3.959 0.901 ... -249
    Ar 1.527 2.672 1.78 ... -190
    Kr 1.357 2.374 3.74 2.6 -157
    Xe 1.177 2.053 5.86 2.4 -112

     

    Because of the lack of reactivity of the noble gases, they are often used when an nonreactive atmosphere is needed, such as in welding. Due to their low boiling points, noble gases are also cryogens in their liquid forms. One familiar use of helium is in balloons and blimps, since it is buoyant in the atmosphere, and unlike hydrogen, nonreactive. Another familiar use is as lighting in gas discharge lamps. Referred to popularly as neon lights, they can contain other noble gases, or mixtures of the gases.

     

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