4 Be 9.012

Beryllium

Alkaline earth metal Beryllium solid

[He] 2s² · 2 · 2

← Li Lithium B Boron →

A light, extremely stiff and severely toxic metal. Beryllium beats steel six times over on stiffness per unit mass, and it is nearly transparent to X-rays — a combination no other element offers.

3D model

Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.

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Atomic properties

Atomic number: 4
Atomic mass: 9.012 а.е.м.
Electron configuration: [He] 2s²
Electrons per shell: 2 · 2
Block: s-block
Group: Alkaline earth metals
Period: 2
Electronegativity (Pauling): 1.57
Electronegativity (Allen): 1.58
Atomic radius: 112 pm
Covalent radius: 96 pm
Van der Waals radius: 153 pm
Ionisation energy 1: 899.5 kJ/mol
Ionisation energy 2: 1 757.1 kJ/mol
Ionisation energy 3: 14 849 kJ/mol
Electron affinity: 0 kJ/mol
Common oxidation states: +2
Oxidation states: +2

Physical properties

State at 25 °C: solid
Density: 1.85 g/cm³
Melting point: 1 560 K · 1 286.9 °C
Boiling point: 2 742 K · 2 468.9 °C
Speed of sound: 12 890 m/s

Thermal properties

Heat of fusion: 12.2 kJ/mol
Heat of vaporisation: 292 kJ/mol
Specific heat capacity: 1.825 J/(g·K)
Thermal conductivity: 200 W/(m·K)

Mechanical properties

Young's modulus: 287 GPa
Shear modulus: 132 GPa
Bulk modulus: 130 GPa
Poisson ratio: 0.032
Mohs hardness: 5.5
Brinell hardness: 600 MPa

Electrical and magnetic properties

Electrical resistivity: 36 nΩ·m
Magnetic ordering: diamagnetic
Curie point: no data
Néel point: no data
Superconducting point: 0.026 K

Crystal structure

Crystal structure: hexagonal close-packed (hcp)
Lattice constants: a = 228.58 pm · c = 358.43 pm

Abundance

In the crust: 2.8 mg/kg
In the ocean: 6·10⁻⁷ mg/L
In the universe: 0.001 mg/kg
In the human body: 4·10⁻⁵ mg/kg

Isotopes

Isotope	Abundance	Half-life	Decay mode
⁹Be	100 %	stable	—
¹⁰Be	—	1.39 Myr	β−

Beryllium-10, with a 1.4-million-year half-life, is made in the atmosphere by cosmic rays and is used to date ice cores and rock surfaces.

Discovery

Year of discovery: 1798
Discovered by: Louis Nicolas Vauquelin
Where: France
Origin of the name: named after the mineral beryl, in which it was discovered

History

Louis Vauquelin isolated the oxide of a new element in 1798 from beryl and emerald, having noticed that their composition did not reduce to known substances. The pure metal waited until 1828, when Wöhler and Bussy reached it independently.

Where it occurs

2.8 mg/kg in the crust. The main minerals are beryl — whose clear varieties are emerald and aquamarine — and bertrandite. Most mining is in Utah.

How it is produced

From bertrandite and beryl via the hydroxide, then the fluoride, which magnesium reduces. Output is small: world production runs to hundreds of tonnes a year.

Role in living things

No biological role. The body treats beryllium as a foreign antigen, and some people develop a lasting immune sensitisation to it.

Safety

Inhaling dust or fume causes berylliosis, a chronic granulomatous lung disease that can appear years after a single exposure. Beryllium compounds are carcinogenic.

Uses

Windows for X-ray tubes and detectors — beryllium barely absorbs soft X-rays
Beryllium bronze: a non-magnetic, non-sparking alloy for tools in explosive atmospheres
Mirrors for space telescopes, including the primary of James Webb
Neutron moderator and reflector in nuclear reactors
Aerospace structures where stiffness at low mass matters

Curiosities

Beryllium is one of the few elements with an even proton count and only a single stable isotope.
Emerald is beryl coloured by chromium; aquamarine is the same beryl with iron.
James Chadwick discovered the neutron in 1932 by bombarding beryllium with alpha particles.
Beryllium-8 lives 10⁻¹⁶ seconds — that gap in the mass table is why stars must build carbon in a three-body step.
The James Webb telescope's primary mirror is beryllium because it barely deforms on cooling to 50 K.