Inert gases in Mendeleyev's table are elements of the main subgroup of the VIII group: helium, neon, argon, krypton, xenon and radon, and the last is a radioactive element. They are called also noble gases.
Electronic structure of inert gases
All inert gases have a complete, steady configuration of external electronic level: at helium it is a doublet, at other gases – an octet. Each of them finishes the corresponding period in Mendeleyev's table.
Inert gases in the nature
All inert gases, except radioactive radon, can be found in composition of atmospheric air. Helium is the most widespread element in space after hydrogen. The sun for 10% consists of this noble gas formed of hydrogen on reaction of nuclear fusion with allocation of positrons and antineutrino.
Physical properties of noble gases
Inert gases are presented by one-atomic molecules. Under usual conditions helium, neon, argon, krypton and xenon – gases without color and a smell, badly soluble in water. The more their atomic number, the is higher than temperature of boiling and melting. Helium has unique properties: it remains liquid even at the lowest temperatures, up to absolute zero, without being exposed to crystallization. It is possible to crystallize helium only under pressure of 25 atmospheres. Besides, at this gas the lowest temperature of boiling from all substances.
Chemical properties of noble gases
Long time was considered that inert gases do not form connections at all. However experimentally under special conditions fluorides and oxides of xenon which existence was predicted by the theorist Laynus Poling were received.
As apply inert gases
Thanks to the outstanding physical and chemical properties, inert gases are widely used in science and technology. So, by means of liquid helium receive ultralow temperatures, and mix of helium and oxygen in the ratio 4:1 it is used as the artificial atmosphere for breath of divers. As helium – the lightest gas after hydrogen, with it is often filled by airships, probes and balloons. Its carrying power is equal to 93% of the carrying power of hydrogen. Neon, argon, krypton and xenon are applied in lighting engineering – production of gas-discharge tubes. At transmission of electric current through the tubes filled with neon or argon, gas begins to shine, and color of this radiation depends on gas pressure. Argon as the cheapest of noble gases is used for creation of the inert atmosphere when carrying out chemical reactions which products interact with oxygen.