What Is Helium? The Complete Guide to the Element and Its Uses

Helium is a colorless, odorless gas with the chemical symbol He and atomic number 2. It’s the lightest of the noble gases and the second-lightest element overall, sitting right after hydrogen.

Helium is completely inert and colder as a liquid than anything else in existence, which is why it turns up in medical scanners, leak-testing rigs, welding setups, and semiconductor lines.

Sounds great, right?

What isn’t so great is its availability. While helium is one of the most abundant elements in the universe, it’s genuinely scarce and expensive to source here on Earth. 

This guide covers where helium sits on the periodic table, its atomic makeup and properties, where it comes from, and how helium is used.

WestAir supplies helium across California and Arizona.

Where Is Helium on the Periodic Table?

Helium sits at the top right of the periodic table in group 18, as element number 2 in period 1. It belongs to the s-block and is the first and lightest member of the noble gas family.

Its group placement explains its behavior. The noble gases all share full outer electron shells, which leaves them stable and reluctant to react.

Every other noble gas carries eight electrons in its outer shell, but helium gets away with just two, because its single shell only has room for two.

How Many Protons and Electrons Does Helium Have?

Helium has two protons and two electrons, which is exactly what its atomic number of 2 tells you. In its most common form it also has two neutrons, giving the nucleus two protons and two neutrons.

Both electrons sit in the first and only shell, written as the electron configuration 1s². Those two are also its valence electrons, and because two electrons completely fill that first shell, helium has a full outer shell with nothing to gain, lose, or share.

That filled shell is the whole story behind helium’s chemistry. A complete outer shell is the most stable arrangement an atom can have, which is why the noble gases barely react.

Helium takes it to the extreme and forms no stable compounds at all. That makes it a genuinely inert gas for shielding and blanketing work, where the whole point is a gas that refuses to interfere.

What Is Helium’s Atomic Mass?

Helium’s atomic mass is about 4.0026, meaning a helium atom weighs roughly four times as much as a hydrogen atom. That figure is the standard atomic weight, which rounds to 4.00 grams per mole for everyday calculations.

The number comes from helium-4, the isotope that makes up virtually all helium on Earth, with its two protons and two neutrons. A much rarer isotope, helium-3, carries only one neutron and accounts for far less than a hundredth of a percent of natural helium.

Helium-3 is used in neutron detection and in cooling systems that reach temperatures ordinary helium can’t, which keeps demand high.

What Are the Properties of Helium?

Helium’s standout properties are the lowest boiling point of any element, an extremely low density, and complete chemical inertness. Together they explain nearly everything helium is used for.

Helium boils at −268.9°C (−452.1°F), just 4.2 K above absolute zero. Liquid helium is the coldest fluid you can practically work with, which is precisely why it cools equipment that needs those temperatures.

Helium is also the only element that won’t freeze solid at normal atmospheric pressure, no matter how cold it gets. Solidifying it takes near-absolute-zero temperatures plus about 25 times atmospheric pressure.

At around one-seventh the density of air, helium is light enough to lift balloons, weather balloons, and airships.

It also won’t burn and it stays chemically unreactive with almost any material it touches.

How Do We Get Helium?

Almost all the helium we use comes from underground, trapped alongside natural gas rather than pulled from the air. Each atom formed over millions of years as radioactive elements like uranium and thorium in the Earth’s crust decayed and shed alpha particles, which are helium nuclei.

Some of that helium seeps upward into the atmosphere, where it sits at only about 5 parts per million. That’s far too dilute to make extracting it from the air worthwhile.

Natural gas is the practical source. Most fields hold only a fraction of a percent—in the U.S. extraction generally starts to pay off above 0.3 percent, and the richest known deposits reach several percent. There’s a lot more to how helium forms and gets extracted, however.

In the universe, the picture flips completely. Helium is the second most abundant element after hydrogen, making up about a quarter of all ordinary matter by mass, forged in the cores of stars and during the first few minutes after the Big Bang.

When Was Helium Discovered?

Helium was discovered in 1868, and it was found in the Sun before anyone found it on Earth. During a total solar eclipse, astronomer Pierre Janssen spotted a yellow line in the Sun’s spectrum that matched no known element.

Months later, Norman Lockyer saw the same line and argued it belonged to a new element, naming it after helios, the Greek word for the Sun. For nearly three decades it stayed a purely solar curiosity that many chemists doubted.

The proof arrived in 1895, when William Ramsay isolated helium on Earth from a uranium mineral called cleveite, with Per Teodor Cleve and Nils Abraham Langlet confirming it independently in Sweden. Helium is still the only element identified in space before it was found here. There are other surprising facts about helium.

What Are Helium’s Uses?

Helium is used wherever industry needs extreme cold, a chemically inert atmosphere, or a gas that slips through the smallest gaps. Here’s the full rundown of what helium does:

• Medical imaging: liquid helium cools the superconducting magnets inside MRI scanners to near absolute zero, and hospitals depend on it for several other clinical uses as well.
• Leak detection: helium’s tiny atoms pass through openings other gases can’t, which makes it the standard tracer for finding leaks in sealed systems.
• Welding and metal work: blended into a shielding gas, helium raises heat input for cleaner welds on aluminum and thick sections, which is why it shows up in aluminum welding.
• Electronics and semiconductors: it shields chips and fiber optics from contamination during manufacturing.
• Lab analysis: helium works as a carrier gas in gas chromatography, moving samples through the instrument without reacting with them.
• Cryogenics and research: as liquid helium, it enables superconductors, particle accelerators, and low-temperature physics.
• Diving: a helium-oxygen blend called heliox lets divers breathe safely at deep pressures.

The right helium grade depends on the job. For example, welding doesn’t require ultra-pure helium, while semiconductor manufacturers have to use ultra-high-purity helium.

How Safe Is Helium to Handle?

Helium is safe to handle under normal conditions, but it can become dangerous when it builds up in an enclosed space. The main hazard is straightforward: helium displaces the oxygen in a room or a tank, and someone breathing a helium-rich atmosphere can lose consciousness with no warning.

The gas itself is non-toxic, so the risk isn’t poisoning. It’s what helium pushes out of the way.

Liquid helium adds another hazard. At cryogenic temperatures it can cause severe cold burns, and a small amount sealed in a container expands into a far greater volume of gas as it warms, enough to rupture the vessel.

Compressed helium cylinders are a separate risk, since the gas is stored under high pressure and a damaged cylinder or valve can fail violently.

Why Is Helium in Short Supply?

Helium is in short supply because it’s finite, non-renewable, and constantly leaving the planet. Once an atom reaches open air, it’s light enough to escape Earth’s gravity for good, so the supply we tap can’t be replaced on any human timescale.

Only a small number of natural gas fields hold enough helium to extract economically, which concentrates production in a few countries and leaves the market exposed to disruption. That tight supply is why buyers periodically run into a helium shortage and why helium is so expensive.

Plan your usage ahead of time and work with a supplier who can source helium reliably, and you can avoid being without helium when you need it.

Tyler O'Brien

Tyler is a results-driven marketing professional specializing in the industrial gases and equipment industry, bringing his 10 years of technical expertise and digital marketing acumen to the complex industrial gas B2B environment.