However, in the early sixties Neil Barlett discovered some exceptions. Noble gases were Initially thought to be entirely chemically unreactive and were called inert gases. Helium is used to create an inert atmosphere during the melting and welding of easily oxidizable metals. For instance, argon is used to manufacture gas-filled electric light bulbs to prevent the oxidation of tungsten filaments, prolonging the bulb’s life. The high stability of noble gases attests to their chemical inertness, which finds many industrial applications. Noble gases resist electron additions as their valence shells are already complete, and the incoming electron needs to enter a higher principal quantum shell. Meaning, energy is required to add an additional electron to a gaseous atom. Noble gases also have positive electron affinity values. The removal of an electron requires the input of a large amount of energy, which is unfavorable. This is because these elements have stable electron configurations with complete octets. Yet, noble gases have high first ionization energies compared to all other elements in the periodic table. Moving down the group, the elements exhibit an increase in boiling points, densities, and atomic radii, which consequently leads to the decline of ionization energies of each successive element. Radon is the only radioactive element from group 18. ![]() ![]() ![]() These elements occur as monatomic species and exist as gases under room-temperature. The nonmetallic elements categorized under group 18 – helium, neon, argon, krypton, xenon, and radon – are called noble gases.
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