Everything about Noble Gas totally explained
The
noble gases are the non-metal, chemically inert elements in group 18 of the
periodic table. Chemically, the noble gases are very stable due to having the maximum number of
valence electrons their outer shell can hold. Noble gases rarely react with other elements since they're already stable. Under normal conditions, they occur as odorless, colorless,
monatomic gases. Each of them has its melting and boiling point close together, so that only a small temperature range exists for each noble gas in which it's a liquid. Noble gases have numerous important applications in lighting, welding and space technology. The six known noble gases are:
helium (He),
neon (Ne),
argon (Ar),
krypton (Kr),
xenon (Xe) and
radon (Rn).
The synthetic elements
ununquadium (Uuq) and/or
ununoctium (Uuo) may also turn out to be noble gases.
Etymology
"Noble gas" is the translation of the German
Edelgas, which was in use as early as 1898 by
Hugo Erdmann. This refers to the extremely low level of reactivity under normal conditions. The noble gases have also been referred to as
inert gases, but these terms are not strictly accurate because several of them do take part in chemical reactions. Another old term is
rare gases, although
argon forms a fairly considerable part (0.93% by volume, 1.29% by mass) of the
Earth's
atmosphere.
History
The existence of noble gases wasn't known until after the advent of the
periodic table. In the late nineteenth century,
Lord Rayleigh discovered that some samples of
nitrogen from the air were of a different density than nitrogen resulting from
chemical reactions. Along with scientist
William Ramsay, Lord Rayleigh theorized that the nitrogen extracted from air was associated with another gas, argon. With this discovery, they realized that a whole class of
gases was missing from the
periodic table. Eventually, all the known noble gases except for helium were discovered in the air, with argon being much more common than the others, and the table was completed. Helium was detected
spectrographically in the
Sun in 1868. The isolation of helium on Earth had to wait until 1895. Under
standard conditions, the noble gases all occur as
monatomic gases.
Chemical makeup
Noble gases have full
valence electron shells. Valence electrons are the outermost
electrons of an
atom and are normally the only
electrons which can participate in
chemical bonding. According to
atomic theory derived from
quantum mechanics and experimental trends,
atoms with full valence electron shells are extraordinarily stable and therefore don't form
chemical bonds.
All of them exhibit an extremely low chemical reactivity and very few
noble gas compounds have been prepared. No conventional compounds of helium or neon have yet been prepared, while xenon and krypton are known to show some reactivity in the laboratory. Recently argon compounds have also been successfully characterised. The noble gases' lack of
reactivity can be explained in terms of them having a "complete valence shell". They have little tendency to gain or lose electrons. The noble gases have high
ionization energies and negligible
electronegativities. The noble gases have very weak inter-atomic forces of attraction, and consequently very low
melting points and
boiling points. This is why they're all
monatomic gases under normal conditions, even those with larger
atomic masses than many normally solid elements.
Applications
One of the most commonly encountered uses of the noble gases in everyday life is in lighting.
Argon is often used as a suitable safe and inert atmosphere for the inside of filament
light bulbs, and is also used as an inert atmosphere in the synthesis of air and moisture sensitive compounds (as an alternative for
nitrogen). Some of the noble gases glow distinctive colors when used inside lighting tubes (
neon lights).
Helium, due to its nonreactivity (compared with flammable
hydrogen) and lightness, is often used in
blimps and
balloons. Helium and argon are commonly used to shield a welding arc, and the surrounding base metal from the atmosphere during welding.
Krypton is also used in lasers, which are used by doctors for eye surgery.
Xenon is used in
xenon arc lamps, and it has anaesthetic properties.
Physical properties
|- align="center" bgcolor="#EDEDED"
! Property
! colspan="6" | Inert Gas
|- align="center"
| Element number
| 2
| 10
| 18
| 36
| 54
| 86
|- align="center"
| Element name
|
Helium
|
Neon
|
Argon
|
Krypton
|
Xenon
|
Radon
|- align="center"
| Density (g/dm³)
| 0.1786
| 0.9002
| 1.7818
| 3.708
| 5.851
| 9.97
|- align="center"
| Atomic radius (nm)
| 0.050
| 0.070
| 0.094
| 0.109
| 0.130
| -
|- align="center"
| Boiling point (°C)
| -268.83
| -245.92
| -185.81
| -151.7
| -106.6
| -62
|- align="center"
| Melting point (°C)
| -272
| -248.52
| -189.6
| -157
| -111.5
| -71
|- align="center"
|
Dynamic Viscosity (Pa-s)
| 1.863E-05
| 2.974E-05
| 2.099E-05
| 2.329E-05
| 2.110E-05
| --
|- align="center"
|
Mean Free Path at
STP(nm)
| 192.665
| 135.355
| 68.332
| 52.337
| 37.878
| --
Noble gas notation
The noble gases can be used in conjunction with the
electron configuration notation to make what is called the
Noble Gas Notation. For example: while the electron notation of the element carbon is 1s²2s² 2p², the Noble Gas notation would be [He] 2s²2p².
This notation makes the identification of elements faster, and is shorter and easier than writing out the full notation of orbitals.
Further Information
Get more info on 'Noble Gas'.
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