Noble Gases

The nonmetallic elements categorized under group 18 – helium, neon, argon, krypton, xenon, and radon – are called noble gases. These elements occur as monatomic species and exist as gases under room-temperature. Radon is the only radioactive element from group 18. 

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. 

Yet, noble gases have high first ionization energies compared to all other elements in the periodic table. This is because these elements have stable electron configurations with complete octets. The removal of an electron requires the input of a large amount of energy, which is unfavorable. 

Noble gases also have positive electron affinity values. Meaning, energy is required to add an additional electron to a gaseous atom. Noble gases resist electron additions as their valence shells are already complete, and the incoming electron needs to enter a higher principal quantum shell. 

The high stability of noble gases attests to their chemical inertness, which finds many industrial applications. For instance, argon is used to manufa