Helium (He)


Helium is a chemical element with the atomic number 2 in the periodic table. With 1.38 parts per million of abundance, it’s the second most plentiful chemical element in Earth’s atmosphere after hydrogen. 

Element 2 is classified as a member of the noble gases family of elements, i.e in Group 18 (VIIIA) of the periodic table. This non-toxic chemical has an extremely stable, closed-shell electronic configuration that does not allow the formation of compounds with any other substance under normal conditions.

Despite being labeled as a relatively harmless chemical, helium gas is safe only when used properly. Indeed, floating balloons filled with helium are the most loved party decor of any celebration and fun event. But as a simple asphyxiant, helium may lead to adverse health effects upon inhalation. 

Fact Box

Chemical and Physical Properties of Helium

The symbol in the periodic table of elements: He 

Atomic number: 2

Atomic weight (mass): 4.00260 g.mol-1

Group number: 18

Period: 1 (s-block)

Color: Colorless

Physical state: Gas

Half-life: From less than 10-9 seconds to 806.7 milliseconds

Electronegativity according to Pauling: Unknown

Density: 0.178*10-3 g.cm-3 at 20 °C

Melting point: −272.20°C, −457.96°F, 0.95 K

Boiling point: −268.928°C, −452.07°F, 4.222 K

Van der Waals radius: 0.118 nm

Ionic radius: Unknown

Isotopes: 9

Most characteristic isotope: 4He

Electronic shell: 1s2

The energy of the first ionization: 2372 kJ.mol-1

The energy of the second ionization: N/A

Discovery date: In 1868 by Pierre Jules César Janssen, in 1895 by Sir William Ramsay, and independently by Per Teodor Cleve and Nils Abraham Langlet

With the periodic table symbol He, atomic number 2, atomic mass of 4.00260 g.mol-1, and electron configuration 1s2, helium is a colorless, odorless, tasteless, and non-combustible noble gas. It reaches its boiling point at −268.928°C, −452.07°F, 4.222 K, while the melting point is achieved at −272.20°C, −457.96°F, 0.95 K. 

This member of the noble gases family of elements has an unknown electronegativity according to Pauling, whereas the atomic radius according to van der Waals is 0.118 nm.

Element 2 mainly exists in gaseous and liquid forms. When the helium gas is exposed to low temperatures, it condenses to liquid helium. In contact with very cold H2O, liquid helium can trigger violent boiling of the water.                       

How Was Helium Discovered?

The first scientific evidence on the existence of element 2 was provided by the French astronomer Jules Janssen (1824 – 1907) on August 18th, 1868. His full name is Pierre Jules César Janssen and he’s credited with the discovery of the gaseous nature of the solar chromosphere.

The Discovery of Jules Janssen

In 1868, this French astronomer was intrigued by the solar eclipse that occurred on November 15th that year. It was one of the rare annual hybrid solar eclipses that sparked Janssen’s curiosity even more and motivated him to study the prominences in the Sun’s corona. By spectroscopically analyzing the sunlight coming directly from the eclipsed Sun, Janssen observed a yellow line in the solar spectrum that he could not relate to any other already discovered chemical element. 

This particular wavelength in the Sun’s light was a clear sign to Janssen that a new chemical element stemming from the Sun can be found on Earth as well. By making this discovery, this French astronomer paved the way for scientists to further understand the nature of stars in our Universe. 

However, the existence of helium was not welcomed by all scientists since most of them believed that the Sun is too far from them to be ever able to derive any scientific evidence on its structure and nature.

The Contribution of Sir William Ramsay

Despite all odds and lack of technological means at those times, the Scottish chemist Sir William Ramsay succeeded to isolate element 2. By working meticulously on noble gases in his London laboratory, Sir Ramsay also managed to scientifically prove the existence of helium on Earth by treating a sample of cleveite (radioactive uranium residue) with sulfuric acid in 1895.

SIr Ramsey sent his findings on helium to his colleagues Norman Lockyer and Sir William Crookes, who were able to confirm the evidence and identify helium as a new chemical element. 

The Contribution of Nils Langlet and Per Theodor Cleve

At the same time, two Swedish scientists, Nils Langlet and Per Theodor Cleve at Uppsala, Sweden, also succeeded in isolating the first sample of element 2 in a lab and becoming the first scientists to measure the atomic weight of helium.  

How Did Helium Get Its Name?

The name of this chemical element originates from the Greek word ‘helios‘, which is a term that personifies the Sun. This notion refers to the fact that helium was first detected in the Sun’s corona

Element 2 was named ‘helium’ by the English chemists Joseph Norman Lockyer and Edward Frankland in 1868 after they confirmed the scientific evidence on the new element provided by Sir William Ramsey. 

Where Can You Find Helium?

Helium comprises around 23% of the entire elemental mass of the Universe as one of the major constituents of the giant gaseous planets, such as Jupiter. It also comprises about 45% of the mass of the Sun. 

Formed in the Big Bang nucleosynthesis, helium in the Universe is generated by the nuclear fusion of nitrogen contained in stars. The heat and pressure formed in the process at the core of said stars triggered a fusion of hydrogen atoms, which further led to the formation of large amounts of helium. 

However, most of the helium quantities found on Earth originate from the natural radioactive decay of the elements uranium and thorium. Even though this gaseous element cannot be contained in Earth’s crust since it constantly escapes into the atmosphere, traces of element 2 can be found in uranium and thorium-bearing minerals. With an occurrence of 8 parts per billion, helium is the 71st most abundant element in Earth’s crust.

All commercially utilized quantities of helium are obtained from natural gases in which helium is often found trapped. In the United States, a series of natural gas fields are the main source of helium in the world. Texas, Pennsylvania, Oklahoma, Louisiana, Ohio, Colorado, West Virginia, Wyoming, New Mexico, Arkansas, North Dakota, Alaska, Utah, Kansas, and California are counted toward the largest natural gas producers in the world, including helium. 

Helium in Everyday Life

The second most abundant chemical element in the Universe possess some chemical properties that make helium indispensable and find practical application in the following instances:

  • Helium’s most popular use is in weather balloons, as well as a carrier gas in some industrial operations;
  • Liquid helium is used as a cryogenic coolant in closed systems and superconducting magnet coils used in MRI machines;
  • Being lighter than air and non-flammable, helium is an ideal fill for party balloons and some types of airships;
  • Element 2 is also commonly used in both lasers and arc welding;
  • This chemical element has a practical use as an inert pressurizing gas for rocket fuel;
  • Manufacturers of semiconductors use helium as a purging agent;
  • In medicine, helium has a specific application in human cryogenics. Namely, it’s used for preserving human organs prior to life-saving transplantations. In the realm of cryogenics, there are two observed forms of the most frequently used helium-4 isotope: liquid helium I (the warm form) and liquid helium II (the cold form). 
  • Helium is the gas that makes party balloons fly.

How Dangerous Is Helium?

Helium is considered hazardous by OSHA 29 CFR 1910.1200 (Hazard Communication Standard). Even though element 2 is classified as a non-toxic and non-flammable element, it’s a simple asphyxiant. 

To begin with, our body needs a constant supply of oxygen to function properly. All organs and tissues of the body receive oxygenated blood via the process of cellular respiration. Namely, red blood cells transfer oxygen molecules to other cells of the body to produce energy for physical, physiological, cellular, and metabolic functions.   

Since it has no color, smell, and taste, helium can swiftly displace oxygen from the air without the affected person noticing it. This oxygen deprivation can lead to severe life-endangering consequences. 

Neurons are especially sensitive to reduced oxygen levels. Even 2-3 minutes without oxygen may lead to fatal outcomes due to a lack of oxygen supply to the brain. Also, while the helium gas itself won’t directly damage the lungs, it may cause oxygen deprivation of the respiratory system. 

Hence, the first symptoms and health conditions that alert to exposure to large quantities of this noble gas primarily affect the central nervous system and the lungs. They are displayed in a form of:

  • Headache;
  • Dizziness;
  • Nausea;
  • Lightheadedness;
  • Confusion;
  • Disorientation;
  • Asphyxiation;
  • Air embolism;
  • Bleeding of the lungs;
  • Hypoxemia (abnormally low levels of oxygen in the blood);
  • Loss of consciousness due to lack of oxygen supply to the brain;
  • Suffocation and lung damage due to lack of oxygen in the lungs.

The health effects that may occur after helium exposure are typically acute (short-term) ones, but the lung and brain damage caused by excess inhalation of helium is irreversible. In addition, skin contact with liquid helium can cause frostbites. 

In more serious cases, inhaling helium from a commercially available pressurized tank can form helium bubbles within the smaller arteries in the organs of our body, including our brain. Labeled as aneurysms, these gaseous ‘bubbles’ can rupture the arteries and cause internal bleeding which is a potentially life-threatening condition.

How Does Helium Change the Sound of Our Voice?

Inhaling helium from helium-filled balloons doesn’t actually change our voice. Being lighter than the air we inhale, it only makes sound waves travel faster across our vocal cords. 

In this way, they resonate with a higher pitched sound and produce that characteristic ‘helium voice’. But, no matter how fun this sounds, please don’t forget that inhaling helium can be extremely dangerous

Environmental Effects of Helium

Helium poses no danger to the geological, biological, or aquatic systems of our environment. Being one of the most lightweight substances, helium easily escapes into the atmosphere and has no known biological role. 

Isotopes of Helium

There are 9 observed isotopes of helium, among which only two are stable. With a half-life of 806.7 milliseconds, helium-8 is the radioisotope of helium with the longest half-life. The most commonly found form of helium in the Universe is the helium-4 isotope. 

Nuclide[6] Z N Isotopic mass (Da)[7]

[n 1]


[resonance width]



[n 2]



[n 3]

Spin and


[n 4][n 5]

Natural abundance (mole fraction)
Normal proportion Range of variation

[n 6]

2 0 2.015894(2) ≪ 10−9 s[8] p (>99.99%) 2H 0+#
β+ (<0.01%) 2H

[n 7]

2 1 3.01602932265(22) Stable[n 8] 1/2+ 1.34(3)×10−6 4.6×10−10−4.1×10−5

[n 7]

2 2 4.00260325413(6) Stable 0+ 0.99999866(3) 0.999959-1
5He 2 3 5.012057(21) 700(30)×10−24 s n 4He 3/2−

[n 9]

2 4 6.01888589(6) 806.92(24) ms β (99.99%) 6Li 0+
β, α (2.8×10−4%) 4He,


7He 2 5 7.027991(8) 2.51(7)×10−21 s

[159(28) keV]

n 6He (3/2)−

[n 10]

2 6 8.03393439(10) 119.1(12) ms β (83%) 8Li 0+
β,n (16.1%) 7Li
β, fission (0.9%) 5He, 


9He 2 7 9.04395(5) 2.5(23)×10−21 s n 8He 1/2+#
10He 2 8 10.05282(10) 3.1(20)×10−21 s 2n 8He 0+

Source: Wikipedia

List of Helium Compounds 

Helium is a completely inert gas. This chemical element does not react and doesn’t form compounds with any of the elements of the periodic table under normal conditions. 

However, the repulsive forces between helium and other atoms may be overcome by high pressure. In this way, helium can form a crystalline compound with sodium. Formation of gas hydrates, i.e. clathrates, is also achievable with helium under pressure in ice, as well as in other small molecules such as nitrogen.

In the Mendeleev oxidation table, the predicted oxidation state of element 2 is 0 because helium doesn’t gain or lose any electrons as a chemically non-reactive substance. 

5 Interesting Facts and Explanations

  1. Element 2 is the second lightest element in the Universe, after hydrogen. Until 1953, it was believed that helium existed only in its gaseous aggregate state. 
  2. Helium is the only chemical element in the periodic table that does not adopt a solid aggregate form at normal pressure, regardless of the temperature it’s exposed to.
  3. In 1882, the Italian scientist Luigi Palmieri observed the same yellow line in the spectrum of gases emitted by Vesuvius like the one discovered by Janssen in 1868.
  4. The popular balloon gas is a mixture of helium and other atmospheric gases, including nitrogen, oxygen, and carbon dioxide.
  5. Even though inhaling helium from a pressurized helium tank may look like a fun thing to do, in reality, this is a very dangerous practice that may lead to severe health consequences, such as lung collapse, loss of consciousness, and death. 

Chemical Property and physical property of element Helium

Symbol of Helium: He
Name: Helium
Atomic Number of Helium: 2
Group of Helium: Noble Gas
Crystal Structure of Helium: Hexagonal
Atomic Weight of Helium: 4.002602
Shells of Helium: 2
Orbitals of Helium: 1s2
Valence of Helium: 0
Melting Point of Helium: 0.95
Boiling Point of Helium: 4.215
Electro Negativity of Helium: 0
Covalent Radius of Helium: 0.93 Å
Ionic Radius of Helium:
Atomic Radius of Helium: 0.49 Å
Atomic Volume of Helium: 19.5 cm³/mol
Name Origin of Helium: Greek: hêlios (sun).
Discovered of Helium By: Sir William Ramsey, Nils Langet, P.T.Cleve
Year: 1895
Location: Scotland/Sweden
Pronounced of Helium: HEE-li-em
Oxydation States of Helium: 0
Density of Helium: 0.0001787 g/cm³
Uses of Helium: Used in balloons, deep sea diving & welding. Also used in very low temperature research.
Description of Helium: Soft silvery-white metal. Lightest of metals. Accounts for only 0.0007% of the earth crust.