Element in Focus: Hydrogen

Hydrogen (Element 1: H)

Hydrogen is the simplest chemical element. It is composed of a single proton and one electron in its most common form, and it is the most abundant element in the universe, accounting for approximately 75% of normal matter by mass and over 90% of all atoms. On Earth, hydrogen is mostly found bound in water and organic molecules. Free hydrogen gas (H₂) is rare in our atmosphere because it is so light that it escapes into space over time.

The scientific discovery of hydrogen dates back to the 18th century, when British chemist Henry Cavendish first identified it as a distinct substance in 1766. He called it “inflammable air” and demonstrated that it formed water when burned. In 1783, French chemist Antoine Lavoisier named it hydrogène, meaning “water-former,” establishing hydrogen as a fundamental element and helping to disprove the idea that water was an element itself.

Hydrogen is colorless, odorless, and tasteless in its natural state as a diatomic gas (H₂). It is highly flammable and can form explosive mixtures with air in concentrations between 18% and 59%. It plays a central role in acid-base chemistry, where the hydrogen ion (H⁺) defines acidity, and can also act as a reducing agent or form hydride ions (H⁻) in metal compounds. Hydrogen bonding – a weak attraction between hydrogen and electronegative atoms like oxygen or nitrogen – is also essential in the structure of water and biological molecules like DNA.

Hydrogen is used widely in industry. The most common uses are in ammonia production for fertilizers, petroleum refining (hydrocracking), and as a coolant gas in electric generators. Most commercial hydrogen is currently produced by steam methane reforming, a fossil-fuel-intensive process. However, hydrogen is also gaining attention as a potential clean energy carrier – especially when made via electrolysis powered by renewable energy (so-called “green hydrogen”).

Other applications include weather balloons, welding, leak detection, and hydrogen fuel cells. In aerospace, hydrogen has been used in rocket fuel (as liquid hydrogen) and in nickel–hydrogen batteries for satellites. In the biological world, hydrogen plays a role in microbial metabolism, and one of its isotopes, deuterium, is used in metabolic tracing and nuclear fusion research.

Physical Data at a Glance

 Isotopes of Hydrogen

Hydrogen has three naturally occurring isotopes:

• Protium (¹H): The most common form, with one proton and no neutrons. Makes up more than 99.98% of natural hydrogen.

• Deuterium (²H or D): Stable, with one proton and one neutron. Occurs naturally at about 0.015% abundance and is used in nuclear reactors and heavy water.

• Tritium (³H or T): Radioactive, with one proton and two neutrons. Used in self-powered lighting and nuclear fusion research. It has a half-life of about 12.3 years.

Safety Notes

Hydrogen is non-toxic but presents significant flammability and explosion risks:

• Forms explosive mixtures with air in concentrations between 18% and 59%.

• Burns with an almost invisible pale blue flame, making leaks difficult to detect without sensors.

• Displaces oxygen in confined spaces, posing an asphyxiation risk.

• Can cause hydrogen embrittlement in metals, making storage and transport a challenge (NASA Safety Guidelines).

Hydrogen systems must include good ventilation, leak detection, and flame arrestors for safety.

Further Exploration

Hydrogen – Periodic Table of Videos (University of Nottingham)

This short and engaging video explores hydrogen’s properties and uses with real lab demonstrations and accessible explanations from chemistry professors at the University of Nottingham.