Beryllium
Atomic Data
| Atomic Number | 4 |
| Symbol | Be |
| Atomic Weight | 9.0122 u |
| Density (STP) | 1.85 g/cm³ |
| Melting Point | 1286.85 °C (1560 K) |
| Boiling Point | 2468.85 °C (2742 K) |
| Electronegativity | 1.57 (Pauling) |
| Electron Config. | 1s² 2s² |
| Oxidation States | +2 |
| Phase at STP | Solid |
| Category | Alkaline-earth metal |
| Period / Group | 2 / 2 |
| CAS Number | 7440-41-7 |
Electron Configuration
1s2 2s2
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| Total | 4 | 4 | ||
Isotopes of Beryllium
Beryllium has only one stable isotope, beryllium-9, which accounts for 100% of naturally occurring beryllium. All other isotopes are radioactive, with beryllium-10 being notable for its use in geochronology thanks to its 1.39-million-year half-life.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Beryllium-9 | ⁹Be | 4 | 5 | 100% | Stable |
| Beryllium-10 | ₁₀Be | 4 | 6 | Trace | Radioactive (t½ = 1.39 Myr) |
| Beryllium-7 | ⁷Be | 4 | 3 | Trace | Radioactive (t½ = 53.22 d) |
Abundance & Occurrence
Beryllium is a genuinely rare element, averaging about 2.8 parts per million in Earth's crust — comparable to tin and less abundant than lithium. It does not occur as a free metal in nature; instead it is locked into silicate minerals, chiefly beryl (Be3Al2Si6O18), which forms the gemstones emerald and aquamarine. The USA, China, and Kazakhstan hold the bulk of global reserves.
Earth's Crust — Selected Rare Elements (ppm, relative scale)
Global Beryllium Reserves by Country (approx. %)
Discovery & History
Safety & Handling
- Inhalation hazard — chronic beryllium disease (berylliosis): Breathing beryllium dust, fumes, or fine particles can cause a severe, progressive granulomatous lung disease. Symptoms may appear years after initial exposure and can be fatal.
- Sensitisation risk: A single exposure can sensitise the immune system; subsequent exposures — even at very low concentrations — can trigger or worsen berylliosis. There is no cure, only symptom management.
- Skin and eye contact: Beryllium dust or soluble salts irritate skin and mucous membranes. Open cuts contaminated with beryllium particles can develop into persistent non-healing ulcers.
- Machining and grinding precautions: All cutting, grinding, or sanding of beryllium metal or beryllium-containing alloys must be performed in enclosed, ventilated enclosures with HEPA filtration. Workers require appropriate respiratory protection (minimum P100 respirators).
- Storage: Store beryllium metal and compounds in sealed, labelled containers away from strong acids and oxidising agents. Dispose of waste as hazardous material under applicable regulations.
- Regulatory context: OSHA's permissible exposure limit (PEL) for beryllium is 0.2 µg/m³ as an 8-hour TWA — one of the strictest metal exposure limits in occupational health. The IARC classifies beryllium compounds as Group 1 confirmed human carcinogens.
Beryllium in the Real World
Real-World Uses
- Aerospace structural alloys — Beryllium-copper (BeCu) alloys, containing 0.5–3% beryllium, are up to six times stronger than pure copper while retaining good electrical and thermal conductivity. They are used in aircraft landing gear bushings, missile guidance components, and the James Webb Space Telescope's mirror substrate.
- X-ray windows — Thin beryllium foils (25–500 µm) are the standard material for X-ray tube windows and synchrotron beamline windows. Beryllium's low atomic number (Z=4) allows X-rays to pass through with minimal absorption, while the foil maintains vacuum separation from the atmosphere.
- Nuclear reactor reflectors — Beryllium reflects and moderates neutrons efficiently because of its low mass and low neutron-absorption cross-section. It is used as a neutron reflector in research reactors and as a structural candidate in fusion reactor blanket designs.
- Gyroscopes and precision instruments — The extreme stiffness and dimensional stability of beryllium make it ideal for inertial navigation gyroscope rotors and precision optical mounts, where thermal expansion must be minimised and dimensional tolerance is critical.
- Audio speaker components — High-end loudspeaker tweeters and diaphragms are made from beryllium foil or beryllium-aluminium alloy. Beryllium's speed of sound (~12,500 m/s, roughly triple that of titanium) allows the diaphragm to operate as a rigid piston well into the ultrasonic range, minimising distortion.
- Neutron sources — When combined with an alpha-particle emitter such as americium-241, beryllium produces neutrons via the (α,n) nuclear reaction. These compact portable neutron sources are used in oil well logging, neutron radiography, and laboratory neutron activation analysis.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
Why is beryllium used in aerospace alloys?
Beryllium has an exceptionally high stiffness-to-weight ratio — about six times stiffer than steel at one-third the density. Beryllium-copper alloys combine this rigidity with good electrical conductivity and corrosion resistance, making them ideal for aircraft structural parts, missile guidance systems, and satellite components where both weight and rigidity matter.
Is beryllium dangerous?
Yes. Inhaling beryllium dust or fumes can cause chronic beryllium disease (berylliosis), a serious and potentially fatal lung condition. Even brief exposures can sensitise the immune system, and the disease may develop years after exposure. Solid beryllium metal handled without generating dust poses much lower risk, but all machining and grinding must be done with strict ventilation and respiratory protection.
How was beryllium discovered?
French chemist Louis-Nicolas Vauquelin identified beryllium as a new element in 1798 while analysing the mineral beryl (emerald). He recognised that the sweet-tasting oxide he extracted was distinct from alumina, and named it glucine from the Greek word for sweet. The metal itself was first isolated independently in 1828 by Friedrich Wöhler and Antoine-Alexandre-Brutus Bussy.
What is beryllium used for in nuclear reactors?
Beryllium serves as a neutron reflector and moderator in some nuclear reactors. When bombarded by alpha particles, it emits neutrons — a property exploited in laboratory neutron sources. Its low neutron-absorption cross-section and high melting point make it valuable in fusion reactor first-wall and breeder blanket designs.
Why does beryllium transmit X-rays?
X-ray transparency depends on atomic number — low-Z elements absorb very little X-radiation. Beryllium (Z=4) has one of the lowest atomic numbers of any solid metal, so X-rays pass through it with minimal attenuation. This makes thin beryllium foils the standard window material for X-ray tubes and synchrotron beamlines, separating the vacuum inside from the atmosphere outside.