Hydrogen (H)
Element 1 · Nonmetal · atomic mass 1.008 u · group 1, period 1
Electron shells: 1
Hydrogen is the lightest element and the most abundant in the universe, consisting of a single proton and a single electron. On Earth it is almost never found alone — it is locked up in water, hydrocarbons and living tissue.
Roughly three quarters of the ordinary matter in the universe by mass is hydrogen.
- Atomic number
- 1
- Atomic mass
- 1.008 u
- Electron configuration
- 1s¹
- Group · period · block
- 1 · 1 · s
- Oxidation states
- −1, +1
- Electronegativity
- 2.2 (Pauling)
- Melting point
- -259 °C
- Boiling point
- -253 °C
- Density
- 0.00008988 g/cm³
- State at 20 °C
- Gas
- Appearance
- Colourless, odourless gas
- Discovered
- Henry Cavendish, 1766
1 protons, and 1 electrons when neutral
IUPAC interval [1.00784, 1.00811]
Alkali metals
What Hydrogen is used for
- Ammonia synthesis for fertiliser
- Refining crude oil
- Fuel cells and green-steel trials
- Rocket propellant
Atomic structure of Hydrogen
A neutral hydrogen atom has 1 protons and 1 electrons. Its most common isotope carries about 0 neutrons, which is where the mass number 1 comes from. Change the neutron count and you have a different isotope of hydrogen; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 1. In orbital notation that is 1s¹, leaving 1 valence electron in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Hydrogen's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Hydrogen sits in the periodic table
Discovery and naming
Hydrogen was discovered by Henry Cavendish in 1766. Its name comes from Greek hydro + genes, "water-forming".
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Hydrogen?
The standard atomic weight of Hydrogen is 1.008 u. Because the natural isotope mix varies between sources, IUPAC publishes it as the interval [1.00784, 1.00811], and 1.008 is the conventional single value to use in calculations.
How many protons, neutrons and electrons does Hydrogen have?
Hydrogen has 1 protons, because the atomic number is the proton count and that is what makes an atom Hydrogen at all. A neutral Hydrogen atom has the same number of electrons, 1. The neutron count varies by isotope; the most common one has about 0, since 1 − 1 = 0.
What is the electron configuration of Hydrogen?
The electron configuration of Hydrogen is 1s¹. Its electrons are arranged 1 across 1 shell.
Is Hydrogen a metal?
No. Hydrogen is classified as a nonmetal, on the right-hand side of the table where elements gain or share electrons rather than losing them.
What group and period is Hydrogen in?
Hydrogen is in group 1 (the alkali metals), period 1, in the s-block. The group is its column and the period is its row.
What is the charge of Hydrogen?
Hydrogen most commonly forms a 1+ or 1− ion. It has 1 electron in its outer shell and loses it readily, which is what the group number tells you.
What is the melting point of Hydrogen?
Hydrogen melts at -259 °C and boils at -253 °C. That puts it in the gases at everyday temperatures.
What is Hydrogen used for?
Ammonia synthesis for fertiliser, Refining crude oil, Fuel cells and green-steel trials, Rocket propellant. Hydrogen is the lightest element and the most abundant in the universe, consisting of a single proton and a single electron.
Who discovered Hydrogen, and where does its name come from?
Hydrogen (H) was discovered by Henry Cavendish in 1766. The name comes from Greek hydro + genes, "water-forming".