Beryllium
Element 4 · Alkaline Earth Metal
Beryllium is a hard, brittle alkaline earth metal with an unusual combination of talents: it is light, extremely stiff, resists corrosion, and lets X-rays pass straight through. Those traits put thin beryllium foil in X-ray machine windows and beryllium parts in aircraft, satellites, and precision instruments. Alloyed with copper it makes springs and tools that never spark. There is a dark side: beryllium dust and fumes can cause a severe lung disease, so machining it demands strict industrial controls. Chemically it behaves as a +2 ion and forms compounds with strong covalent character.
Key facts
| Atomic number | 4 |
|---|---|
| Atomic weight | 9.012 |
| Category | Alkaline Earth Metal |
| Group / Period | 2 / 2 |
| Block | s |
| Electron configuration | 1s2 2s2 |
| Common oxidation states | +2 |
| State at STP | Solid |
| Electronegativity | 1.57 |
| Atomic radius | 112 pm |
| Density | 1.85 g/cm³ |
| Melting point | 1287 °C |
| Boiling point | 2469 °C |
Occurrence
Beryllium is scarce in Earth's crust, mined mainly from the ores beryl and bertrandite. The gemstones emerald and aquamarine are colored varieties of beryl, the same mineral family.
Applications
X-ray tube windows
Aerospace and satellite structures
Beryllium-copper non-sparking tools
Neutron reflectors in nuclear reactors
Precision instruments and mirrors
Common compounds
- Beryllium oxide (BeO)
- Beryl (Be3Al2(SiO3)6)
- Beryllium-copper alloy
- Beryllium fluoride (BeF2)
Emeralds and aquamarines owe their existence to beryllium — both are gemstone varieties of the mineral beryl.
Data source: IUPAC standard atomic weights 2021