Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u, hydrogen is the lightest element on the periodic table. Its monatomic form (H) is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass.
Three reasons Hydrogen stands out
1
Most abundant element in the universe.
2
Powers the Sun through nuclear fusion, releasing enormous amounts of energy.
3
Burns with an almost invisible pale-blue flame, making leaks extremely dangerous.
The atom that lights the stars
Hydrogen looks simple—usually one proton and one electron—but that simplicity powers the cosmos. Gravity squeezes hydrogen nuclei together inside stars, releasing energy through fusion. On Earth it is rarely free for long: it joins oxygen in water and carbon in the molecules of life.
Recognizing Hydrogen in Elementle
If Hydrogen is the mystery element, guesses below atomic number 1 point up and guesses above it point down. Its symbol is H: a green letter matches the same position in that symbol, while a yellow letter belongs in another position.
The family clue turns green for nonmetal guesses. Compare Carbon (C), number 6 and Nitrogen (N), number 7: they share the family clue, but their atomic numbers and symbols help you tell them apart.
Values are reference data, not a specification for every temperature, pressure, or allotrope. Unknown properties are left unavailable. Superheavy-element predictions remain uncertain.
The introduction and original editorial story are adapted from Wikipedia contributors via Periodic-Table-JSON. Element descriptions and their adaptations are available under CC BY-SA 3.0. Numerical attributes use the PubChem periodic-table dataset, retrieved September 22, 2026.