Q.Nobel gases have comparatively large atomic radius. Why?

Ease of liquefaction rises with atomic size (stronger dispersion forces); xenon is the largest of the options, so it liquefies most easily.

Noble gases are held together only by weak van der Waals (London dispersion) forces. These forces increase with the number of electrons/polarisability, i.e. with atomic size. Down the group Ne < Ar < Kr < Xe in size, so boiling points and ease of liquefaction increase in the same order. Xenon, bein …

Noble gases (except He) have a completely filled valence shell, ns2 np6.

The noble gases owe their chemical inertness to a completely filled valence shell. For Ne, Ar, Kr, Xe and Rn the outermost configuration is ns2 np6 (a stable octet of eight electrons). Helium is the only exception, with the configuration 1s2 (a filled first shell, which is also a s …

Argon (about 0.93% of air) is the most abundant noble gas in the atmosphere.

The noble gases occur in air in the order of abundance: Ar >> Ne > He > Kr > Xe (and radon only in traces). Argon is present at roughly 0.93% by volume, which makes it the third most abundant component of dry air after nitrogen and oxygen, and by …

Radon (Rn) is the radioactive member of the noble gases — option (D).

The noble gases (Group 18) are He, Ne, Ar, Kr, Xe and Rn. All of the lighter ones (He, Ne, Ar, Kr, Xe) are stable, non-radioactive gases. Radon (Rn), the heaviest naturally occurring noble gas, has no stable isotope — it is produced by the ra …

Helium boils at about 4.2 K, the lowest boiling point of any substance/gas.

Boiling point rises with the strength of intermolecular forces. Helium is a monatomic noble gas with the weakest van der Waals (dispersion) forces because of its tiny, tightly held electron cloud, so it has the lowest boiling point of any element, about …