264 | The History and Use of Our Earth’s Chemical Elements (1840–1905) and Niles Langlet (1868–1936), independently found helium in the decay gases
264 | The History and Use of Our Earth’s Chemical Elements (1840–1905) and Niles Langlet (1868–1936), independently found helium in the decay gases
of uranium at the same time. Nevertheless, Ramsay is credited with the discovery of helium. Helium in the Earth is replaced by the decay of radioactive elements in the Earth’s crust. Alpha decay produces particles ( 4 He ++ ) known as alpha particles, which can become helium atoms after they capture two electrons. This new helium works its way to the surface of the Earth and escapes into the atmosphere where, in time, it escapes into space.
CommonUses Helium has many uses.
As an inert gas, it is used as the atmosphere in which to “grow” silicon crystals (computer chips). As a lifting gas, it is used to inflate weather balloons and lighter-than-air ships (blimps) similar to the ones seen taking TV pictures above football games. Even though helium has less lifting power than hydrogen, it is used for all lighter-than-air ships because it is noncombusti- ble and thus safer than hydrogen. In addition to blimps, toy balloons are filled with helium.
In arc welding, it is used as an inert gas shield that releases great heat for very long and heavy welds. Helium prevents oxidation of the metal being welded, thus preventing burning and corrosion of the metal. This is one of the major uses of helium.
Helium is used for low-temperature research (–272.2°C or –434°F). It has become important as a coolant for superconducting electrical systems that, when cooled, offer little resistance to the electrons passing through a conductor (wire or magnet). When the electrons are “stripped” from the helium atom, a positive He ++ ion results. The positive helium ions (nuclei) occur in both natural and man-made radioactive emissions and are referred to as alpha particles. Helium ions (alpha particles) are used in high-energy physics to study the nature of matter.
In gas discharge lasers, helium transfers the energy to the laser gas such as carbon dioxide or another inert gas.
As an inert gas with heat-transfer capability, helium is used in gas-cooled nuclear power reactors, which operate at a higher efficiency than liquid-cooled nuclear reactors. The world’s largest particle accelerators use liquid helium to cool their superconducting magnets. Astronomers use liquid helium to cool their detecting instruments. If this equipment is kept cool, the “thermal noise” produced at higher temperatures is reduced.
Helium is mixed with oxygen in air tanks for scuba diving and deep-sea diving because it is less soluble in divers’ blood than is nitrogen. Divers have a greater chance of experiencing “nitrogen narcosis” and becoming disoriented and also of getting “the bends” when using compressed air (nitrogen–oxygen mixture), a condition in which the nitrogen forms bubbles in the blood as divers ascend. This condition is not only painful but even life-threatening, particularly if divers become so disoriented that they do not know where they are, or if they rise to the surface too quickly. Because helium is less soluble in the blood than nitrogen, the chances of deep-sea divers experiencing the bends and becoming disoriented are lessened when they are breathing a helium–oxygen mixture.
An interesting effect caused by breathing helium is the change in one’s voice when speak- ing. Because helium is less dense than air, the vocal cords produce sounds at a higher pitch than normal and the speaker sounds like Donald Duck.
ExamplesofCompounds
265 The noble elements were always thought to be inert and not very reactive because their outer
Guide to the Elements |
shells have full complements of electrons. Under special circumstances some of these inert elements can be forced to combine with a few other elements, particularly the more active halogens.
Compounds of the three heavier noble gases, krypton (Kr), xenon (Xe), and radon (Rn), have been made, but the formation of stable compounds of the lighter noble gases, helium (He), neon (Ne), and argon (Ar), has been more difficult. Recently a positive ion has been formed by combining hydrogen with helium (HeH + ).
Helium is also the result of fusion reactions wherein the nuclei of heavy hydrogen are “fused” to form atoms of helium. The result is the release of great amounts of energy. Fusion is the physical or nuclear reaction (not chemical reaction) that takes place in the sun and in thermonuclear weapons (e.g., the hydrogen bomb).
Hazards Being inert, the noble gases are nontoxic. However, they can act as asphyxiant gases that
can kill because of oxygen deprivations.
A possible hazard is when He ++ nuclei, as alpha particles, are accelerated to high speeds and bombard a target. Alpha particles can be stopped by several inches of air or a piece of card- board. As high-energy, charged particles generated from man-made or natural radioactivity, alpha particles can cause damage, but they are not as damaging to our bodies as are very short wavelength gamma rays, which can only be stopped by lead shielding.
NEON SYMBOL:Ne PERIOD:2 GROUP:18(VIIIA) ATOMICNO:10
ATOMICMASS:20.179amu VALENCE:0 OXIDATIONSTATE:0 NATURALSTATE:Gas ORIGINOFNAME: Theword“neon”wasderivedfromtheGreekwordneos,meaning
“new.” ISOTOPES:Thereareatotalof11isotopesofneon,threeofwhicharestable.TheyareNe- 20,whichmakesup90.48%ofthenaturalabundanceofneononEarth;Ne-21,which contributesjust0.27%toalltheneonfoundinnature;andNe-22,whichcontributes 9.25%tothenaturalabundanceofneon.Alltheotherisotopeshavehalf-livesranging from3.746×10 -21 secondsto3.38minutes.