Skip to main content


At the origin of the Universe

Hydrogen is the most abundant element in the Universe. It is present on Earth in great quantities combined with other elements. Therefore, it must be extracted from these elements to obtain hydrogen gas, which has many practical applications.

Properties of the atom

  • Atomic mass:
    1,007825 g.mol -1

  • Atomic ray:
    25 pm

  • Electronic configuration:

  • Crystalline structure:

The hydrogen molecule (H2), which is sometimes called “dihydrogen”, is the oldest and simplest molecule in our Universe. It is found in every star, including the Sun, which draws its energy from the transformation of hydrogen into helium during a thermonuclear reaction. It is made up of two hydrogen atoms, which are the first two elements to have been formed more than 13 billion years ago.

  • Name: Hydrogen
  • Symbol: H
  • Number: 1
  • Chemical series: Non-metal
  • Group: 1
  • Period: 1
  • Block: s

Hydrogen is found in great quantities on Earth combined with other elements, such as in water and hydrocarbons, but it is barely present in our atmosphere, which contains just 0.00005%. This is why, to obtain hydrogen in the gaseous form, it must be produced through extraction from the molecules that contain it and it must be stored.

For many years, hydrogen has been used for multiple industrial applications in very diverse sectors of activity. It is mainly used to make fuel cleaner by eliminating the sulfur that is naturally found in crude oil. When hydrogen is combined with a fuel cell, it is also a source of sustainable energy, a field that is developing rapidly.

Hydrogen is the smallest and lightest molecule in the Universe. It is 50000 times smaller than the thickness of a hair and one liter of hydrogen gas weighs 90 mg under normal conditions of pressure and temperature; this is equal to three postage stamps.

Learn More

The basic identifying features of hydrogen

NAME: “Dihydrogen” is the scientific name of what is commonly referred to as “hydrogen”.


COMPOSITION: Two interlocking hydrogen atoms.

AGE: It is the oldest molecule in the Universe. It appeared after the Big Bang, more than 13 billion years ago.

SIZE: It is the smallest molecule that exists in the Universe.

WEIGHT: It is the lightest molecule in the Universe.

ADDRESSE: It is the most abundant molecule in the Universe and is found in the stars, like the Sun, as well as in gaseous planets, like Jupiter.

SPECIFICS: The hydrogen molecule is colorless, odorless and non-toxic.

ROLE: It is the Sun’s fuel, enabling the star to transmit heat and light to the Earth. It is also the fuel of choice for rockets and is already being used to propel electric cars that produce their own power onboard. Hydrogen is used as a reagent in many industries, including oil refining.

At the origin of the Universe

More than 13 billion years ago, just a few minutes after the Big Bang, the protons that compose the nuclei of hydrogen came into existence. At this stage in the formation of the Universe, the temperature was extremely high—close to a billion degrees.

The Universe then began a phase of expansion and cooling. After several million years, it was sufficiently cold to allow hydrogen molecules to form. These molecules gave rise to immense clouds known as “nebulas”, which initiate the formation of the stars.

A nebula was also behind the origin of the Sun about five billion years ago. Our star is mainly composed of hydrogen and helium, resulting from the thermonuclear fusion reaction that enables it to produce energy. These two elements are the lightest and the most abundant in the Universe.

The four giant gaseous planets in our solar system—Jupiter, Saturn, Uranus and Neptune—are also mainly formed out of hydrogen.

But the Earth’s atmosphere is almost totally lacking in hydrogen because our planet’s gravitational field is not strong enough to retain these extremely light molecules. However, we do find numerous sources of hydrogen on Earth, where it is combined with other elements, in water and hydrocarbons, for example.

Learn more with the Gas Encyclopedia

Its discovery

Hydrogen was discovered in 1766 by British physicist Cavendish. It was by combining metals with strong acids that Cavendish noticed the formation of a gas that he called “inflammable air” because it was combustible. This extremely light gas was in fact hydrogen. He then noticed that burning it produced water vapor (steam).

In 1783, French chemist Lavoisier gave this light gas the name of “hydrogen”, which is Greek for “that which generates water”.

It was not until 1838 that German chemist Schönbein discovered the fuel cell effect, which enables the production of electricity out of hydrogen and oxygen. The first fuel cell model was built in a laboratory three years later by Sir William Grove, an English scientist.

Thereafter, many other experiments involving the hydrogen molecule were carried out. In 1898, Dewar successfully liquefied hydrogen by cooling it down to -252,87°C. His liquefaction process was improved on by another chemist and physicist, the Frenchman Georges Claude, who was also one of the founders of Air Liquide.

Early uses of hydrogen

One of the first uses of hydrogen in the field of transportation dates back to the 18th century, when Charles and Robert made the first manned flight in a balloon called the “hydrogen gas aerostat”. This was one of the first inventions that allowed humans to take to the skies untethered.

In 1932, Bacon resumed the study of fuel cell technology, which resulted in the first fuel cell prototype in 1953. This prototype served as a model for the fuel cell used for the Apollo-series space missions, which led to the 1969 Moon landing.

In the 20th century, hydrogen found another application in the space industry. In 1943, liquid hydrogen was tested as rocket fuel at Ohio State University. After testing proved successful, it became the fuel of choice for numerous rockets and launchers, including Ariane 5.

Today, hydrogen is one of the 21st century’s vectors of energy for clean transportation.

© GettyImages - Westend61 - J.Melin