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It is given by the ratio of the pressure on a body to the fractional decrease in volume. A measure of the propensity of a substance to evaporate. It is defined as the equilibrium pressure exerted by the gas produced above a substance in a closed system. This Site has been carefully prepared for your visit, and we ask you to honour and agree to the following terms and conditions when using this Site.
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Nor shall the RSC be in any event liable for any damage to your computer equipment or software which may occur on account of your access to or use of the Site, or your downloading of materials, data, text, software, or images from the Site, whether caused by a virus, bug or otherwise. Jump to main content. Periodic Table. Glossary Allotropes Some elements exist in several different structural forms, called allotropes.
Allotropes -. Glossary Group A vertical column in the periodic table. Fact box. Glossary Image explanation Murray Robertson is the artist behind the images which make up Visual Elements. Appearance The description of the element in its natural form. Biological role The role of the element in humans, animals and plants. Natural abundance Where the element is most commonly found in nature, and how it is sourced commercially. Uses and properties. Image explanation. Helium was detected in the sun by its spectral lines many years before it was found on Earth.
A colourless, odourless gas that is totally unreactive. It is also used to keep satellite instruments cool and was used to cool the liquid oxygen and hydrogen that powered the Apollo space vehicles. Because of its low density helium is often used to fill decorative balloons, weather balloons and airships. Hydrogen was once used to fill balloons but it is dangerously reactive. Because it is very unreactive, helium is used to provide an inert protective atmosphere for making fibre optics and semiconductors, and for arc welding.
Helium is also used to detect leaks, such as in car air-conditioning systems, and because it diffuses quickly it is used to inflate car airbags after impact.
Helium-neon gas lasers are used to scan barcodes in supermarket checkouts. A new use for helium is a helium-ion microscope that gives better image resolution than a scanning electron microscope. Biological role. Helium has no known biological role. It is non-toxic. Natural abundance.
After hydrogen, helium is the second most abundant element in the universe. It is present in all stars. It was, and is still being, formed from alpha-particle decay of radioactive elements in the Earth. Some of the helium formed escapes into the atmosphere, which contains about 5 parts per million by volume.
This is a dynamic balance, with the low-density helium continually escaping to outer space. It is uneconomical to extract helium from the air. Help text not available for this section currently. Elements and Periodic Table History. In , Pierre J. Janssen travelled to India to measure the solar spectrum during a total eclipse and observed a new yellow line which indicated a new element. Joseph Norman Lockyer recorded the same line by observing the sun through London smog and, assuming the new element to be a metal, he named it helium.
In , the Italian Luigi Palmieri found the same line the spectrum of gases emitted by Vesuvius, as did the American William Hillebrand in when he collected the gas given off by the mineral uraninite UO2 as it dissolves in acid. However, it was Per Teodor Cleve and Nils Abraham Langer at Uppsala, Sweden, in , who repeated that experiment and confirmed it was helium and measured its atomic weight.
Atomic data. Glossary Common oxidation states The oxidation state of an atom is a measure of the degree of oxidation of an atom. Oxidation states and isotopes. Glossary Data for this section been provided by the British Geological Survey. Relative supply risk An integrated supply risk index from 1 very low risk to 10 very high risk.
Recycling rate The percentage of a commodity which is recycled. Substitutability The availability of suitable substitutes for a given commodity.
Reserve distribution The percentage of the world reserves located in the country with the largest reserves. Political stability of top producer A percentile rank for the political stability of the top producing country, derived from World Bank governance indicators. Political stability of top reserve holder A percentile rank for the political stability of the country with the largest reserves, derived from World Bank governance indicators. Supply risk. Relative supply risk 6. Young's modulus A measure of the stiffness of a substance.
Shear modulus A measure of how difficult it is to deform a material. Bulk modulus A measure of how difficult it is to compress a substance. Vapour pressure A measure of the propensity of a substance to evaporate. Pressure and temperature data — advanced. Listen to Helium Podcast Transcript :. You're listening to Chemistry in its element brought to you by Chemistry World , the magazine of the Royal Society of Chemistry.
Hello, this week we're almost at the top of the periodic table because we're taking a look at the lighter than air gas helium. But for this chemist a helium filled bobbing balloon is actually a source of pain and not a source of pleasure. Here's Peter Wothers. We are all familiar with the lighter-than-air gas helium, but whenever I see a balloon floating on a string, I feel a little sad.
It's not because I'm a miserable old so-and-so - it's just because, unlike the happy child on the other end of the string, I am aware of the valuable resource that's about to be lost forever.
Helium is the second most abundant element in the universe, but here on earth, it's rather rare. Most people guess that we extract helium from the air, but actually we dig it out of the ground. Helium can be found in certain parts of the world, notably in Texas, as a minor component in some sources of natural gas.
The interesting thing is how this gas gets into the ground in the first place. Helium is odorless. Extremely low. Helium is a tasteless gas. It is completely inert. Chemical Properties of Helium. Chemical properties are simply the characteristics that define how the element reacts with other substances or changes from one to another substance.
And, the chemical properties are seen only during a chemical reaction. Chemical Formula. Reactivity with Water. Less soluble in water compared to any other gas.
Non Toxic. Health Effects of Helium. Humans have no sense that they can detect the presence of Helium. Although Helium is non-toxic and inert, it can act as a simple asphyxiant by displacing oxygen in the air to the below-required levels to support life.
Excessive inhalation of Helium can cause dizziness, nausea, vomiting, loss of consciousness, and death. Death may result from confusion, errors in judgment, loss of consciousness that prevents self-rescue. At low concentrations of oxygen, unconsciousness and death may occur in seconds without any warning.
Personnel, including rescue workers, should not enter areas where the concentration of oxygen is lower to Color Helium is colourless Phase Gas When cooled, it condenses to liquid helium, which is the only element that does not solidify at normal pressure irrespective of the temperature Density Helium gas is less dense compared to any other known gas except hydrogen and it is about one seventh as dense as air Odor Helium is odorless Viscosity Extremely low Taste Helium is a tasteless gas Compounds It is completely inert.
Gas When cooled, it condenses to liquid helium, which is the only element that does not solidify at normal pressure irrespective of the temperature. Geologic conditions in Texas, Oklahoma, and Kansas make the natural gas in these areas some of the most helium-rich in the world with concentrations between 0.
What is helium used for, and why is it a strategic natural resource? Perhaps the most familiar use of helium is as a safe, non-flammable gas to fill party and parade balloons. However, helium is a critical component in many fields, including scientific research, medical technology, high-tech manufacturing, space exploration, and national defense.
Here are a few examples:. For many of these applications, there is no substitute for helium. Helium is a non-renewable resource found in recoverable quantities in only a few locations around the world, many of which are being depleted. Accordingly, the U. What is the Federal role in managing this strategic resource? The BLM operates and maintains a helium storage reservoir, enrichment plant, and pipeline system near Amarillo, Texas, that supplies over 40 percent of domestic demand for helium. The BLM supplies crude helium to private helium refining companies which in turn refine the helium and market it to consumers.
How is the Federal Helium Program Funded? The Federal Helium Program operates using non-appropriated funds i.
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