The elements are: Helium (Z = 2), Neon (10),
Argon (18), Krypton (36), Xenon (54) and Radon (86).
As per our normal rules of electronic
configurations and explained properties, noble gases have a valence of 0. They shells are all filled with paired
electrons in all energy states possible.
There is no energy state available to get a new electron. Neither the nucleus allows an electron to
go out. The ionization energy is very
very high. They are inert and do not
react with other elements in the periodic table. They are single atom molecules. It is found not long ago that they too form
compounds. At least some of them do.
The electrons in Helium are held closely to
the nucleus as it is a very small atom.
In Radon the outermost electrons
are in the principal quantum number : n = 6.
That is very far. The radius of
atoms increase proportional (roughly for an idea) to square of n. Thus the outermost electrons are loosely
bound as compared to Helium. So its
ionization energy is less.
A few hundred compounds of noble gases
have been discovered/invented/formed in the laboratories In the last two
decades. Xenon, Krypton and Argon show
very small reactivity. Their reactivity
is in the order of Ne < He < Ar < Kr < Xe < Rn. Due
to radioactivity, Radon does not actually form as many compounds as Xenon.
decades ago in 20th century, scientists including Linus Pauling have
postulated and predicted regarding the compounds of Noble gases. A lot
of research went into these. At very low temperatures, the compounds
with more stability.
Some compounds with Helium and Neon are
formed, but they are not neutral and very stable. Existence and formation of Xenon Octa Floride
Xe F8, Xenon Hexafloride Xe F6 and Kripton hexa Floride Kr F6 are predicted with
logical explanations and conditions. As Foride is the most electronegative element,
it can make these elements react. These
compounds are thermodynamically (energy wise) and kinetically unstable. Some compounds with Oxygen too are observed.
Xenon can exist in the oxidation states of +2, +4, +6
or +8. So Xe F2, Xe F4, Xe F6, Xe O4, Sodium perxenate: Na4 (Xe O6)
are formed in the laboratories. The
equation of Xenon Florides is:
Xe + n
* F2 => Xe F_2n
Xenon Floride is available in the
market. It is used as a fluorinating
agent, where deficiency of Fluorine is there or to furnish Fluorine in a
reaction. We can form compounds with
Xenon and Carbon, Xenon bonded to
Nitrogen element, Oxygen, Chlorine, Gold Mercury and Xenon too.
Some compounds with other elements are
formed at low temperatures (below zero deg. C).
Due to high Radioactivity of Radon, it is
less reactive (as opposed to general prediction) than Xenon. Radon floride and Oxides are formed.
Krypton is found in oxidation state 2 in
many compounds. Kr F2 is most
common. Krypton forms compounds with
Nitrogen and Oxygen that are stable at temperatures below -60 deg. C.
Helium has been found to form : He
H+ ion. Argon Floride (Ar F) and
Krypton Floride Kr F exist in excited electronic state. They are used
in ultraviolet lasers in performing surgeries and some fabrication.
Under very high pressure and low
temperatures, Carbon compounds with Noble gases can be formed.