Helium (He), chemical element, inert gas of Group 18 (noble gases) of the periodic table. The second lightest element (only hydrogen is lighter), helium is a colourless, odourless, and tasteless gas that becomes liquid at −268.9 °C (−452 °F). The boiling and freezing points of helium are lower than those of any other known substance. Helium, along with neon, argon, krypton, xenon, and radon, is an inert gas (also known as a noble gas) – that is, it does not normally react with other elements to form chemical compounds. Unlike most of these, however, helium is, at least for us, a very common gas.

• Why Helium Inert Gases
• Is Helium Inert Gas

Helium, along with neon, argon, krypton, xenon, and radon, is an inert gas (also known as a noble gas) – that is, it does not normally react with other elements to form chemical compounds. Unlike most of these, however, helium is, at least for us, a very common gas. Despite lacking the usual property of such gases – eight electrons in its outer atomic shell – helium is still classified as an inert gas because its outer shell, which holds just two electrons, is still full.

THE INERT/NOBLE GASES

• Helium is heads the noble gas group in the periodic table and has the second lightest element after hydrogen. The main sources of helium in the world are a series of natural gas fields in the United States. Its characteristics are odorless, tasteless, colorless and non-toxic.
• High-quality 80 cu ft steel inert gas cylinder. This is perfect for Helium, Nitrogen, Argon, or CO2/Nitrogen mixes. Heavy-duty construction with thick walls and durable painted finish. The tank has great low-temperature delivery. Guaranteed date of manufacture or hydro test within 180 days. DOT, ISO/UN, and TC approved. All cylinder ship empty.

The discovery of helium during the 1800s paralleled the discovery of the inert gases more generally. Beginning with Henry Cavendish in the late 1700s, early chemists realized that air contained small amounts of a special gas which did not participate in any chemical reactions. In the late 1800s, further research by John Strutt Lord Rayleigh confirmed the existence of this gas, and called it argon, borrowing as inspiration a Greek term for “inactive.” Shortly afterward, William Crookes identified another non-reacting gas given off by uranium samples, and called it helium.

In chemical terms, we now understand why these mysterious gases did not react as expected. The “inert gases” – since renamed noble gases, because under extremely specific conditions they can actually be made to react actively with other chemicals – are six gases with no colour and no smell: helium, neon, argon, krypton, xenon, and radon. To understand why they behave this way, it is necessary to delve very deeply into atomic theory.

Atoms contain three basic building blocks: protons and neutrons which are packed very closely together in a dense nucleus, and electrons which zip around the nucleus at high speed. Although the paths these electrons travel are effectively random, rather than the coherent orbits described in the early twentieth century by Ernest Rutherford (which still form the basis for much high school-level chemistry), it is still useful to think of these electrons as sticking within distinct orbits or “shells,” of varying distance from the nucleus of their atom. Usually the outermost shell can safely hold up to eight electrons, although with hydrogen and helium (because of their extremely small nuclei), the outer shell holds only two electrons.

Ionic bonds form between elements, creating chemical compounds, when atoms with partially empty outer shells come together. Some elements (those on the left of the periodic table) tend to give off free electrons, reducing their number in the outermost shell until it is entirely empty; those on the right of the periodic table, except for the noble gases themselves, tend to take electrons from other atoms, filling up their outer shell entirely. This leads to the formation of such commonly known compounds as table salt (sodium chloride), in which sodium gives up one electron and chlorine gains one electron.

Inert gases, however, already have full outer shells of electrons. Consequently, they tend neither to give away free electrons, nor to take electrons from other atoms. For quite some time, it was believed that it would be entirely impossible to create compounds from noble gases. Scientists now realize that it is difficult but not impossible, under carefully controlled conditions. Specifically, a number of compounds have been created using the heavier noble gases. However, no confirmed compounds currently exist containing either helium or neon.

HELIUM AS A NOBLE/INERT GAS

All other noble or inert gases operate on an effectively identical premise: their outer shell is capable of holding eight electrons, and it holds electrons – and, therefore, it neither takes nor gives up any electrons when mixing with other chemicals. Helium is slightly different: its outer shell is only capable of holding two electrons. However, it is still filled to capacity, with just two electrons. As a result, helium does not form compounds with other chemical elements.

By contrast, hydrogen also has an outer shell capable of holding two electrons, but it actually has only one electron. For this reason hydrogen can form many compounds, including one which will be most familiar to readers, water (H2O), in which each of the hydrogen atoms gives up one electron, and the oxygen atom gains two electrons. In contrast, helium neither gives nor takes electrons, and therefore does not form compounds.

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Helium blimp: Most people have heard of helium being used as a lifting gas for weather balloons, blimps, and party balloons. These are very minor uses of helium. The use that consumes more helium than any other is cooling the magnets in MRI (magnetic resonance imaging) machines in medical facilities. Goodyear blimp photo by Derek Jensen.

What is Helium?

Helium is a chemical element and a colorless, odorless, tasteless, inert gas. It has the smallest atomic radius of any element and the second-lowest atomic weight. It is lighter than air.

Most people know that helium is used as a lifting gas in blimps and party balloons, but they can't name another way in which it is used. The number one use of helium is as a cooling gas for magnetic resonance imaging (MRI) machines used in medical facilities. Other important uses of helium include: a protective gas for welding, an inert gas for controlled atmosphere manufacturing, a fugitive gas used for leak detection, and a low-viscosity gas for pressurized breathing mixtures.

Where Does Helium Come From?

Very little helium is present in Earth's atmosphere. It is such a light element that Earth's gravity cannot hold it. When present at Earth's surface, unconfined helium immediately begins rising until it escapes the planet. That's why party balloons rise!

The helium that is produced commercially is obtained from the ground. Some natural gas fields have enough helium mingled with the gas that it can be extracted at an economical cost. A few fields in the United States contain over 7% helium by volume. Companies that drill for natural gas in these areas produce the natural gas, process it and remove the helium as a byproduct.

Helium-bearing natural gas deposits: Deposit model for helium-bearing natural gas fields in the United States. Helium is produced by the decay of uranium and thorium in granitoid basement rocks. The liberated helium is buoyant and moves toward the surface in porosity associated with basement faults. The helium then moves upward through porous sedimentary cover until it is trapped with natural gas under beds of anhydrite or salt. These are the only laterally-persistent rock types that are able to trap and contain the tiny, buoyant helium atoms. This geological situation only occurs at a few locations in the world and is why rich helium accumulations are rare.

Related:A New Use of Helium - Hard Drives

Why is Helium in Some Natural Gas?

Most of the helium that is removed from natural gas is thought to form from radioactive decay of uranium and thorium in granitoid rocks of Earth's continental crust. As a very light gas, it is buoyant and seeks to move upward as soon as it forms.

The richest helium accumulations are found where three conditions exist: 1) granitoid basement rocks are rich in uranium and thorium; 2) the basement rocks are fractured and faulted to provide escape paths for the helium; and, 3) porous sedimentary rocks above the basement faults are capped an impermeable seal of halite or anhydrite. [1] When all three of these conditions are met, helium might accumulate in the porous sedimentary rock layer.

Helium has the smallest atomic radius of any element, about 0.2 nanometers. So, when it forms and starts moving upward, it can fit through very small pore spaces within the rocks. Halite and anhydrite are the only sedimentary rocks that can block the upward migration of helium atoms. Shales that have their pore spaces plugged with abundant organic materials (kerogen) sometimes serve as a less effective barrier.

Helium-bearing natural gas deposits: Map showing the natural gas fields that serve as important sources of helium in the United States. The natural gas produced from these fields contains between 0.3% to over 7% helium. The helium is removed from the gas for commercial sale. Image by Geology.com using location data from the United States Geological Survey. [2]

Where is Natural Gas Rich in Helium?

Most unprocessed natural gas contains at least trace amounts of helium. Very few natural gas fields contain enough to justify a helium recovery process. A natural gas source must contain at least 0.3% helium to be considered as a potential helium source.

Why Helium Inert Gases

In 2010, all of the natural gas processed for helium in the United States came from fields in Colorado, Kansas, Oklahoma, Texas, Utah, and Wyoming as shown on the accompanying map. The Hugoton Field in Oklahoma, Kansas and Texas; the Panoma Field in Kansas; the Keyes Field in Oklahoma; the Panhandle West and Cliffside Fields in Texas, and the Riley Ridge Field in Wyoming account for most of the helium production in the United States. [2]

During 2010, the United States produced 128 million cubic meters of helium. Of that amount, 53 million cubic meters of helium were extracted from natural gas, and 75 million cubic meters were withdrawn from the National Helium Reserve. Other countries with known production amounts were: Algeria (18 mcm), Qatar (13 mcm), Russia (6 mcm), and Poland (3 mcm). Canada and China produced small but unreported amounts of helium. [3]

Helium in MRI machines: The number one use of helium is cooling the magnets in the MRI (magnetic resonance imaging) machines used to diagnose disease and injury in medical facilities.

A New Use for Helium: The first helium-sealed hard drive was produced in 2013. Helium enables the drive to use less energy, produce less heat, make less noise, take up less space, hold more data and produce fewer vibrations than a standard hard drive. Learn more. Photo copyright iStockphoto / deepblue4you.

Uses of Helium

Helium has a number of properties that make it exceptionally well-suited for certain uses. In some of these uses, helium is the best possible gas to use, and in a few there is no adequate substitute for helium. Several uses of helium along with the properties that make it suitable for the use are described below.

Magnetic Resonance Imaging

Is Helium Inert Gas

The number one use of helium is in the magnetic resonance imaging machines used in medical facilities to assess injuries and diagnose illness. These machines utilize a magnetic field that is produced by a superconducting magnet. These magnets generate an enormous amount of heat. Liquid helium is the cooling substance of choice for regulating the temperature of these magnets. Because helium has the second-lowest specific heat of any gas and the lowest boiling/melting point of any element, there is no foreseen substitute for helium in this very important use.

Lifting Gas

Helium has the second-lowest atomic weight of any element. Only hydrogen has a lower atomic weight. As a lighter-than-air gas, helium has been used as a 'lifting gas' for airships and balloons. Blimps, dirigibles, zeppelins, anti-aircraft balloons, weather balloons and other lighter-than-air craft have all used helium as a lifting gas. It is much safer than hydrogen because it is not flammable. This was the most important category of helium use until the end of World War II. Much lower amounts of helium are now used as a lifting gas.

Purging gas: Helium is used by NASA and the Department of Defense to purge liquid oxygen and liquid hydrogen from fuel tanks and fuel delivery systems of rocket engines. Helium is inert and has a freezing temperature that is so low that it remains a gas through the purging process. A flow of helium into these systems has even been used during emergencies to extinguish fires. Image by NASA.

Purging Gas

Helium has the lowest melting and boiling point of any gas. It melts and boils at temperatures close to absolute zero. Because it remains a gas at very low temperatures, it can be used as a purging gas for fuel tanks and fuel delivery systems that are filled with very cold liquids such as liquid hydrogen and liquid oxygen. Because it is inert and has a low freezing temperature, it can displace these fuels safely without freezing. Large amounts of helium are used by NASA and the Department of Defense for purging rocket propulsion systems.

Controlled Atmosphere Manufacturing

Helium is an inert gas. The only gas with a lower reactivity is neon. This low reactivity makes helium a valuable gas to use in manufacturing and repair processes when an inert atmosphere is required. Helium also has the second-lowest density of any gas along with a very high thermal conductivity. These properties of helium gas make it the atmosphere of choice for many metallurgical processes, growing perfect crystals in chemical vapors, manufacturing optical fibers and other uses.

Leak Detection

Helium has a very low viscosity, a high diffusion coefficient, and the smallest atom of any element. These characteristics make helium very hard to contain. If a system has a leak, helium will escape. Helium gas is therefore used to test high vacuum systems, fuel systems and other containments for leaks.

Helium breathing mixtures: Helium is used to prepare breathing gas mixtures for deep-water diving. Helium is inert and has a low viscosity under pressure which allows easier breathing. Image by NOAA.

Breathing Mixtures

Helium and other inert gases are used to prepare breathing mixtures for deep-water diving and medical treatments. Helium is used here because it is inert, has a very low viscosity and is easier to breathe under pressure than any other gas.

Welding Gas

Helium is used as a protective atmosphere when welding. An inert gas atmosphere protects hot metals from oxidation and other reactions that might occur rapidly at high temperatures.

Uses of helium: Relative amounts of helium consumed by various uses in the United States during 2011. Graph by Geology.com using data from USGS.

Helium: A Nonrenewable Resource

Helium is a gas that is only found where a coincidence of unlikely situations occur. Although it is continually being produced by radioactive mineral decay in Earth's crust, its rate of natural production and accumulation is so slow that it must be considered a nonrenewable resource.

Helium Gluts and Helium Shortages

In 1925 the United States established the National Helium Reserve to serve as a strategic supply of helium for use in airships and for other defense purposes. At that time the country was producing much more helium than was being consumed. After World War II the amount of helium used as a lifting gas declined, but demand for helium as a purging gas when refueling rocket engines and as a coolant in nuclear weapons facilities surged. Still, more helium was being produced than consumed.

In 1995, Congress decided that the National Helium Reserve was not essential and initiated a program to sell the helium as part of the Helium Privatization Act of 1996. [4] For almost two decades Congress allowed the helium to be sold at an enormous discount to free-market prices. Up to 1/2 of the world's helium demand was being met through sales from the National Helium Reserve. In some years more helium was exported out of the United States to other countries than was consumed domestically. [2] Those who purchased helium from the government got a fantastic deal, and those who purchased helium in the free market paid a much higher price.

Dumping of National Helium Reserve stock into the market depressed the price of helium so much that it was being used as a cheap substitute for argon and other gases that have a much less limited supply.

Because commercial helium production was not rewarded or heavily utilized, the market was undersupplied when National Helium Reserve sales were replaced by an auction system in 2014. In the first auction, two bidders purchased the entire yearly allocation of 93 million cubic feet of helium at more than double the previous year's market price. After the auction another 1 billion cubic feet was sold to the same two bidders. [5]

Since the first auction, the price of helium continued to rise because production of new helium falls short of consumption. The price increase has triggered investment in new helium processing plants. However, helium can only be produced from natural gas fields with salt or anhydrate as a trap rock. These only occur in a few parts of the world.

Under current law, the National Helium Reserve will be sold-out by 2021. Hopefully the rising investment in helium recovery plants will be adequate to meet the needs of helium consumers when that important source of helium is gone.