Hydrogen

Hydrogen (symbol: H) is the chemical element with atomic number 1, meaning each atom contains one proton (a positively charged particle in the atom's nucleus). It is the lightest and simplest of all known elements.

Under normal temperature and pressure conditions, hydrogen is a colorless, odorless, and tasteless gas that is easily ignited. It typically exists as a two-atom molecule bonded together (H₂). Throughout the universe, hydrogen is the most abundant substance and is the basic component of stars.

Chemical properties

Hydrogen combines with various other elements. When it burns with oxygen, it produces water (H₂O). It is also part of the natural compounds that make up living matter, such as carbohydrates, proteins, and oils. Hydrogen has three isotopic forms (atoms with the same atomic number but different mass): protium, deuterium, and tritium.

Discovery

In earlier centuries, various chemists observed a gas of this kind being produced when iron was exposed to acid. In the 18th century it was recognized as a distinct element. The name 'hydrogen' comes from Greek words meaning 'water-former', because its combustion produces water.

Uses

In industry, hydrogen is used in the production of ammonia (used as agricultural fertilizer), in oil refining, and in various other chemical processes. It is also used as fuel for high-altitude aircraft and in fuel cells that generate electricity, where the only direct product is water. For this reason, there is ongoing discussion about its potential role in future energy.