Hydrogen
The lightest and most abundant element in the universe.
Inside the Hydrogen atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Hydrogen atom step by step.
Electron configuration
1s1
A neutral Hydrogen atom has 1 electron (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Gas
- Melting point
- 14 K (-259 °C)
- Boiling point
- 20 K (-253 °C)
- Density
- 0.00008988 g/cm³
- Electronegativity
- 2.2 Pauling
- Atomic radius
- 25 pm
- 1st ionization energy
- 1312 kJ/mol
- Category
- Reactive nonmetals
Discovery & naming
- Discovered
- 1766
- Discovered by
- Henry Cavendish
- Origin of name
- Greek 'hydro genes', meaning water-forming.
Notable uses
Ammonia and fuel production, rocket propellant, and a clean-energy carrier.
Where Hydrogen comes from
Big Bang nucleosynthesis
Its nuclei are single protons left over from the first minutes of the universe. Still the most abundant element.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 1
- Atomic mass
- 1.008
- Category
- Reactive nonmetals
- Group · Period
- 1 · 1
- Block
- s-block
- Shells
- 1