Group VIIIA - noble gases
Properties
| Physical Properties:
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- Helium has a boiling point of 4.2K under 1 atm pressure, the lowest boiling point of any substance.
- When an electric current is passed through a tube which contains Neon gas at a low pressure gas, it has a red-orange glow.
- Argon is colourless, odourless and tasteless. It makes up 0.934% of air.
- Krypton is a dense, colorless, odorless atmospheric gas.
- Xenon is a heavy, unreactive stable gas. When Xenon atoms are sufficiently energized, they produce a brilliant white light.
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| Chemical Properties:
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- noble gases exist as single, monatomic gases atoms
- all noble gases have eight valence electrons, a completely filled outer energy level of electrons ('filled' outer shell means two electrons in the outer shell for He and eight electrons in the outer shell for the others). This stable electron arrangement accounts for the nonreactive nature of the noble gases.
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| Abundance:
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- helium is extracted from natural gas wells
- argon are present in about 1% of the Earth's atmosphere, other noble gases are present in trace amounts
- radon is a radioactive gas produced from the radioactive decay of the element radium
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| Common
Compounds and Usages:
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- helium is used to fill balloons, blimps, pressurize liquid fuel in rockets
- helium and argon are used in arc welding and metallurgical processes to protect materials from reacting with nitrogen and oxygen in the air
- argon and nitrogen are used to fill light bulbs and fluorescent tubes to prolong the filament life
- krypton is used to increase the efficiency and brightness of flashlight bulbs and electronic flash in photography
- neon is used to produce the bright orange-red light when electric current is passed through a tube of neon gas at low pressure
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