English translation of the original Chinese article. Publication dates and the extent of recovered text are preserved. Figures retain their original labels. Read the Chinese original.
Did you know? Hydrogen is the most abundant element in the universe. It accounts for as much as 75% of the combined mass of all the elements. The universe may also contain mysterious dark matter, however, whose mass is thought to far exceed that of all the elements combined.
What Kind of Element Is Hydrogen?
PhDSciNet’s short answer: Hydrogen comes first in the periodic table. It has the simplest structure: a neutral hydrogen atom consists of a nucleus containing one proton and one electron outside the nucleus. It is the lightest element. Because elemental hydrogen—hydrogen gas—burns in air to form water, it was given the name “hydrogen”, meaning a maker (genes) of water (hydro).
What Are Hydrogen’s Chemical Properties?
PhDSciNet’s short answer: A hydrogen atom contains only one electron. In common compounds such as water, H₂O, and methane, CH₄, hydrogen has an oxidation state of +1. In some hydrides formed with reactive metals, its oxidation state is −1. In geological structures, hydrogen also occurs as bound water in mineral crystals.[3][1]
How Is Elemental Hydrogen Gas Produced?
PhDSciNet’s short answer: One laboratory method is a displacement reaction between a reactive metal and an acid, in which hydrogen ions gain electrons to form hydrogen gas, H₂. In 1766, the British chemist Henry Cavendish collected and studied this gas, recognizing that it differed from other known gases. Another method is electrolysis of water, splitting water molecules into hydrogen and oxygen gases in a volume ratio of 2:1. Industrially, hydrogen can also be produced by reacting steam with carbon or methane.[1]
What Properties Does Hydrogen Gas Have?
PhDSciNet’s short answer: Hydrogen is a highly flammable gas. Mixed with air under common conditions, its flammable concentration range is approximately 4% to 75% by volume. An ignition source can cause combustion and potentially an explosion. Because it is very light and relatively easy to produce, hydrogen was once used to fill airship envelopes and provide lift. The danger of using such large quantities is readily imaginable, however, and helium gradually replaced hydrogen in this role. Hydrogen releases a great deal of heat when burned and can be used as rocket-engine fuel. It is also commonly used in many important industrial chemical reactions.[2]
Is Hydrogen Gas Toxic?
PhDSciNet’s short answer: Hydrogen is generally not considered a toxic gas, but it cannot replace oxygen. If it accumulates in a poorly ventilated space, it can displace oxygen and cause asphyxiation. Its high flammability is another hazard that must be taken seriously.[2]
An Element That Lights the Sky and Helps Form the World
The Sun is humanity’s earliest and most important source of light, continuously supplying Earth with light and energy. The Sun and the vast majority of stars in the night sky contain large quantities of hydrogen. Through nuclear fusion, the Sun and many other stars convert hydrogen nuclei into helium nuclei, releasing large amounts of light and other types of radiation. When this energy reaches Earth, some was absorbed and stored by ancient plants, becoming the fossil fuels we use today; some drives atmospheric circulation and ocean currents. Many of the heavier elements making up living organisms and our surroundings, meanwhile, are associated with nuclear reactions in stars and stellar evolution.
References in the Original Manuscript
- [United States] Theodore Gray. The Elements: A Visual Exploration of Every Known Atom in the Universe (colour collector’s edition) (Kindle Locations 2770–2789). Posts & Telecom Press. Kindle Edition.
- 2[]Wikipedia, Hydrogen
- 3. Baidu Baike: Hydrogen
- 4. 孙学军. Molecular Hydrogen Biology. Second Military Medical University Press, first edition, April 2013.
Sources for This Factual Revision
- Royal Society of Chemistry: Hydrogen
- US Department of Energy: Hydrogen Safety, Codes, and Standards
- OpenStax Chemistry 2e: rules for oxidation states
Editorial note: Restored from a local original manuscript and factually revised on October 10, 2026. Corrected hydrogen’s oxidation states and combustion conditions, and removed unverified discovery anecdotes and statements about therapeutic effects. The historical publication date and author credit have been retained.
