Hydrogen
nonmetalProperties
| Property | Value |
|---|---|
| Atomic Mass | 1.008 amu |
| Category | nonmetal |
| Group | 1 |
| Period | 1 |
| Electron Configuration | 1s1 |
| Electronegativity | 2.2 (Pauling) |
| Oxidation States | 1, -1 |
| Melting Point | 13.99 K (-259.2 °C) |
| Boiling Point | 20.271 K (-252.9 °C) |
| Density | 0.00008988 g/cm³ |
| Discovered By | Henry Cavendish (1766) |
About Hydrogen
Hydrogen is the simplest atom in the universe — one proton, one electron — and that simplicity is what makes it the reference point for almost everything else in chemistry. Its emission spectrum gave us the Bohr model and the Rydberg constant. Its bond energies anchor the thermochemistry tables. On Earth you almost never encounter it as the free element — H₂ is reactive enough that it gets locked into water, hydrocarbons, and biological molecules. The dihydrogen you do see in a lab usually came from electrolysis or steam reforming, often within an hour of when you needed it. Industrial production passes 90 million tonnes a year, almost all of it consumed on-site for ammonia synthesis (Haber-Bosch) and crude-oil hydrotreating. Hydrogen sits awkwardly above both group 1 and group 17 because it can lose one electron to give H⁺ or gain one to give the hydride H⁻, depending on what it meets.
Fun Fact
The Sun fuses 600 million tonnes of hydrogen into helium every second, and the proton-proton chain that does it has a per-proton half-life of about 9 billion years — which is why stars last as long as they do.
Common Uses
- Steam-reforming feedstock for ammonia and methanol synthesis
- Hydrocracking and hydrodesulfurization of petroleum fractions
- Reducing atmosphere for tungsten and molybdenum metallurgy
- Liquid-hydrogen propellant for upper-stage rocket engines
- PEM fuel cells for backup power and heavy transport