Beryllium

ALKALINE-EARTH METAL · GROUP 2 · PERIOD 2
4
Be
Beryllium
9.0122

Atomic Data

Atomic Number4
SymbolBe
Atomic Weight9.0122 u
Density (STP)1.85 g/cm³
Melting Point1286.85 °C (1560 K)
Boiling Point2468.85 °C (2742 K)
Electronegativity1.57 (Pauling)
Electron Config.1s2 2s2
Oxidation States+2
Phase at STPSolid
CategoryAlkaline-Earth Metal
Period / Group2 / 2
CAS Number7440-41-7

Electron Configuration

K L Be

[He] 2s2

Shell n Subshell Electrons Cumulative
K11s22
L22s24
Total 4 4

Isotopes of Beryllium

Beryllium is monoisotopic — ⁹Be is its only naturally occurring stable isotope, accounting for 100% of all natural Beryllium.

Isotope Symbol Protons Neutrons Abundance Stability
Beryllium-9⁹Be45100Stable

Abundance & Occurrence

Beryllium is present in Earth's crust at approximately 2.8 ppm by mass and at approximately 1 ppm by mass throughout the universe.

Earth's Crust (ppm by mass)

Beryllium
2.8 ppm
Silicon (ref.)
277,000 ppm
Oxygen (ref.)
461,000 ppm

Universe (ppm by mass)

Beryllium
1 ppm
Helium (ref.)
230,000 ppm
Hydrogen (ref.)
739,000 ppm

Discovery & History

1798
Louis-Nicolas Vauquelin — French chemist Vauquelin isolated a new oxide from the mineral beryl and from emerald, recognising it as a distinct sweet-tasting earth; the element was named beryllium (and briefly glucinium) for its Greek root bēryllos.
1828
Friedrich Wöhler & Antoine Bussy — Wöhler and Bussy independently isolated metallic beryllium by reducing beryllium chloride with potassium — Wöhler's paper appearing slightly earlier, though both are credited.
1954
U.S. Atomic Energy Commission — Beryllium was adopted as a neutron reflector and moderator in nuclear weapons and reactors owing to its low neutron-absorption cross-section, driving industrial-scale production for the first time.

Read more about the discovery of the periodic table of elements →

Safety & Handling

  • Inhalation toxicity: Beryllium dust, fumes, and fine particles are acutely toxic by inhalation; even brief exposures can sensitise individuals, and the OSHA permissible exposure limit is 0.2 µg/m3 — among the lowest for any industrial metal.
  • Chronic beryllium disease (berylliosis): Repeated or sensitising exposure causes berylliosis, a debilitating chronic granulomatous lung disease that can progress to respiratory failure; there is no cure.
  • Carcinogenicity: Beryllium and beryllium compounds are classified as Group 1 carcinogens (IARC); inhalation exposure is associated with elevated risk of lung cancer.
  • Skin sensitisation: Beryllium can cause contact dermatitis and skin sensitisation; wounds contaminated with beryllium particles require thorough medical debridement to prevent chronic granuloma formation.
  • Handling requirements: All machining, grinding, or heating of beryllium must be performed in enclosed, ventilated systems with HEPA filtration; workers require respiratory protection and regular medical surveillance.

Real-World Uses

  • Aerospace alloys — Beryllium-aluminium alloys are six times stiffer than steel at one-quarter the weight, making them ideal for aircraft inertial guidance systems, satellite structures, and space telescope mirrors.
  • X-ray windows — Beryllium's very low atomic number makes it nearly transparent to X-rays; thin beryllium foils serve as windows in X-ray tubes, particle accelerator beam pipes, and X-ray spectroscopy detectors.
  • Nuclear reactor components — Beryllium is used as a neutron reflector and moderator in research reactors because it efficiently scatters and slows neutrons with minimal absorption.
  • Audio equipment — Beryllium diaphragms in high-end loudspeaker tweeters and headphones deliver exceptional high-frequency response due to the metal's combination of stiffness, low density, and high internal damping.
  • Electronic components — Copper-beryllium alloys are used in precision springs, electrical connectors, and non-sparking tools for use in explosive environments, combining high conductivity with spring-like elasticity.

Downloadable Resources

Free periodic table reference sheets for classrooms, study sessions, and laboratory use.

Colour PDF Black & White PDF

Frequently Asked Questions

What is beryllium used for?

Beryllium is used in aerospace alloys (beryllium-aluminium and beryllium-copper) for components that must be extremely stiff and lightweight, in X-ray tube windows (beryllium is nearly transparent to X-rays), in nuclear reactor reflectors and moderators, in high-performance audio speaker diaphragms, and in precision springs and electrical connectors made from copper-beryllium alloy.

Is beryllium toxic?

Yes, beryllium is highly toxic. Inhalation of beryllium dust, fumes, or fine particles can cause berylliosis, a serious and potentially fatal chronic lung disease characterised by granuloma formation. Acute beryllium disease from high-level exposure can be immediately life-threatening. Because of its toxicity, beryllium is handled only under strict industrial hygiene controls with dedicated ventilation and personal protective equipment.

Why is beryllium used in X-ray windows?

Beryllium's very low atomic number (Z=4) means its atoms present very little obstacle to X-ray photons, making it nearly transparent to X-radiation. A thin beryllium window transmits X-rays that would be heavily attenuated by glass or metal, while still providing a vacuum-tight seal. This is essential in X-ray tubes, synchrotron beamlines, and X-ray fluorescence instruments.

Is beryllium a metal?

Yes, beryllium is a lightweight alkaline-earth metal with a grey, lustrous appearance. It is the second-lightest structural metal (after lithium), with a density of 1.85 g/cm³, and is notable for having an exceptionally high stiffness-to-weight ratio — about six times stiffer than steel by weight — making it valuable in precision engineering despite its toxicity.