(N/A) Helium: Helium is a non-inflammable and light gas; hence,it is used in filling balloons for meteorological observations.
It is used in gas-cooled nuclear reactors.
Liquid helium (b.p. $4.2 \ K$) is used as a cryogenic agent for carrying out various experiments at low temperatures.
It is used to produce and sustain powerful superconducting magnets,which form an essential part of modern $NMR$ spectrometers and Magnetic Resonance Imaging $(MRI)$ systems for clinical diagnosis.
It is used as a diluent for oxygen in modern diving apparatus due to its very low solubility in blood.
Neon: It is used in discharge tubes and fluorescent bulbs for advertisement display purposes.
Neon bulbs are used in botanical gardens and in greenhouses.
Argon: Argon is used mainly to provide an inert atmosphere in high-temperature metallurgical processes (arc welding of metals or alloys) and for filling electric bulbs.
It is also used in the laboratory for handling substances that are air-sensitive.
Xenon and Krypton: They are used in light bulbs designed for special purposes.