By Ron B. Davis Jr., Georgetown University
Noble gases, especially the lighter ones, such as helium and neon, are made of very small, single atoms that don’t take up much space. They also produce some of the weakest Van der Waals forces or dispersion forces of any gas. This ensures that when two atoms do bump into one another, very little energy is lost and their velocity remains virtually the same.
Gases and Elastic Collision
Gases are mostly empty space, consisting of atoms or molecules that are moving freely and independently of one another, filling whatever sort of container they are placed into.
This gives gases their characteristic compressibility, meaning they can expand or contract to fill their container. Gases have variable volume and variable shape.
Thus, in order for a gas to be as gas-like as possible, its atoms or molecules must take up an infinitesimally small fraction of the total volume the sample occupies. They should also rarely encounter one another, and it should have no effect if they do collide, with no loss of kinetic energy. This is referred to as ‘elastic collision.’
Furthermore, in the case of ideal gases, the number of atoms or molecules of a gas per unit volume at a given temperature should always be the same.
Effectively, this means the less massive the atoms or molecules of gas, the less mass that gas will have per unit volume.
This article comes directly from content in the video series Understanding the Periodic Table. Watch it now, on Wondrium.
Uses in Aviation
This helps explain why helium is the noble gas of choice for aviation and weather balloons. Ideal gas law predicts that a sample of uncompressed helium in our atmosphere, similar to what one might find in a weather balloon, will be only about 15% of the density of our atmosphere.
With that kind of buoyancy, one needs about 1 cubic meter of helium to lift 1 kilogram of mass in the lower atmosphere.
However, if we move up just one space to neon, the gas sample is 71% the mass of a similar volume of air. And if we move on further to argon, and our gas sample would now actually be a little heavier than the air around it.
Use in Deep-sea Diving
Helium is famous for its use in flying devices. But its ideal behavior, and therefore inertness, is also helpful in other applications.
It is used for deep-sea divers because at higher pressures, most components of air tend to dissolve in the blood, including nitrogen, but this has the unwanted effect of making drivers drowsy and impairing their judgment.
Excess oxygen under high pressure is even more dangerous. Helium, by contrast, seems to have no particular effects on the blood at high pressure, so during more advanced deep-sea dives, helium is sometimes used to dilute the oxygen and nitrogen in breathing tanks.
It enables humans to directly explore high-pressure environments under the ocean safely.
An Irreplaceable Cryogen
And because helium atoms do not come together to form a liquid until a temperature of about 4 Kelvin, helium is an irreplaceable cryogen in applications requiring temperatures below even that of liquid nitrogen.
Many superconducting magnets, and the technologies they support, rely on liquid helium to maintain the temperatures needed to operate effectively.
All of this has made helium a coveted strategic natural resource—so much so that the US maintains a strategic helium reserve to ensure that a steady supply is available for scientific and medical applications.
It brings an interesting question to the fore: how do you contain some of the smallest, fastest-moving gas particles in all of nature? The answer is that you do it the same way nature does!
US Helium Reserve
In 1925, the US Helium Reserve was established at the Bush Dome formation, a previously mined deposit of trapped helium and natural gas. There, about 3,000 feet underground, helium collected from other sites was pumped back into the ground for storage under the impermeable rock formations that trapped the original deposit.
At various points in history, this site held over a billion cubic meters of helium gas that could be re-extracted should the need ever arise.
Unfortunately, in 1996, the Reserve was losing money, the Cold War was over, and Federal legislation was passed to deplete the reserve and sell the helium to private vendors.
With so much additional helium suddenly on the market, the price of helium fell. Efforts to recycle plummeted.
Shortage in Future?
Nevertheless, all the helium we have on Earth is due to the slow decay of radioactive elements. Both uranium and thorium transmute into other elements by emitting helium nuclei as alpha particles that eventually claim two electrons to complete the helium atom.
This means that helium shortages may soon become a real problem once again, as more and more uses for helium are developed and demand almost inevitably rises for this one-of-a-kind material.
Common Questions about Helium
In order for a gas to be as gas-like as possible, its atoms or molecules must take up an infinitesimally small fraction of the total volume the sample occupies. They should also rarely encounter one another, and it should have no effect if they do collide, with no loss of kinetic energy. This is referred to as elastic collision.
Helium seems to have no particular effects on the blood at high pressure. So during more advanced deep sea dives, helium is sometimes used to dilute the oxygen and nitrogen in breathing tanks.
It enables humans to directly explore high-pressure environments under the ocean safely.
As helium atoms do not come together to form a liquid until a temperature of about 4 Kelvin, helium is an irreplaceable cryogen in applications requiring temperatures below even that of liquid nitrogen.
Many superconducting magnets and the technologies they support rely on liquid helium to maintain the temperatures needed to operate effectively.
