Hydrogen (H)
Reactive nonmetal · s-block · period 1 · group 1
Colourless, odourless diatomic gas; lightest of all substances.
Hydrogen (symbol H) is chemical element number 1, a reactive nonmetal in group 1, period 1 of the periodic table. Its standard atomic weight is 1.008 and its electron configuration is 1s1. At room temperature it is a gas. Makes up about 75% of the ordinary mass of the universe.
Properties
| Atomic number | 1 |
|---|---|
| Atomic mass | 1.008 |
| Category | Reactive nonmetal |
| Block | s-block |
| Group · Period | 1 · 1 |
| Electron configuration | 1s1 |
| Electrons per shell | 1 |
| State at 25 °C | gas |
| Melting point | 13.99 K |
| Boiling point | 20.27 K |
| Density | 0.08988 g/L |
| Electronegativity (Pauling) | 2.2 |
| Radioactive | No |
| Origin | primordial |
| Discovered | 1766 · Henry Cavendish |
Key facts about Hydrogen
- Makes up about 75% of the ordinary mass of the universe.
- Placed above group 1 but it is a nonmetal — it can lose or gain one electron.
- Burns in air with an almost invisible flame to give only water.
- Liquid hydrogen boils at just 20 K, one of the coldest common liquids.
What Hydrogen is used for
Ammonia synthesis (Haber process), refining fuels, rocket propellant, fuel cells.
Where it sits in the periodic table
Hydrogen is in group 1, period 1, of the s-block. Its electron configuration 1s1 means its outermost shell holds 1 electron, which is what places it here and explains much of its chemistry. See Hydrogen on the interactive table →
Hydrogen — frequently asked questions
What is Hydrogen used for?
Ammonia synthesis (Haber process), refining fuels, rocket propellant, fuel cells.
Is Hydrogen radioactive?
No. Hydrogen has at least one stable isotope and is not radioactive.
What is the electron configuration of Hydrogen?
Hydrogen has the electron configuration 1s1, which is 1 electrons per shell.
What group and period is Hydrogen in?
Hydrogen is in group 1, period 1, in the s-block. Its outer shell holds 1 electron.
Who discovered Hydrogen?
Hydrogen was discovered in 1766 by Henry Cavendish.