Beryllium (Z=4): A Rare Metal with Exceptional Properties

Discovery and Origin

Beryllium (symbol Be, atomic number 4) was identified in 1798 by the French chemist Louis-Nicolas Vauquelin in the mineral beryl. In 1828, Friedrich Wöhler and Antoine Bussy independently isolated the pure metal by reducing beryllium chloride with potassium. The name comes from the Greek beryllos, referring to green beryl (a variety of emerald).

Contribution of beryllium to vital processes

Beryllium is not an essential trace element for living organisms. It does not participate in any known biological processes and can even be toxic. Its presence in biological tissues is generally due to environmental or occupational exposure. Consequence of exposure: various toxic effects, including pulmonary inflammation, liver damage, and enzymatic inhibition. No recognized vital role.

Atomic Structure

Constitution: 4 protons, 4 neutrons (stable isotope), 4 electrons distributed over two electron shells (1s² 2s²).
Isotopes:

• ⁹Be: stable isotope (100%, spin 3/2), nuclear structure used in NMR spectroscopy.
• ¹⁰Be: radioactive cosmogenic isotope (T₁/₂ ≈ 1.39 million years), geochemical and atmospheric tracer.

Physical Properties

• Steel-gray metal, rigid, brittle at room temperature.
• Molar mass: 9.012 g/mol
• Melting point: 1560 K (1287 °C)
• Boiling point: 2744 K (2471 °C)
• Density: 1.848 g/cm³ (very low for a metal).
• Crystal structure: hexagonal close-packed (hcp).
• Low X-ray absorption, high thermal conductivity.

Chemical Reactivity

• Resistant to oxidation at room temperature, forms a thin passivating oxide layer (BeO).
• Slowly reacts with hot water, faster with acids (HCl, H₂SO₄).
• Forms ionic and covalent compounds: beryllates, organoberyllium, etc.
• Amphoteric: exhibits both acidic and basic properties.

Industrial and Technological Applications

• Component in high-performance alloys (beryllium-copper): springs, electrical contacts, non-sparking tools.
• Structural material in aeronautics, space, and defense due to its lightness and rigidity.
• X-ray tube windows, components transparent to X-rays and neutrons.
• Moderator and reflector in nuclear reactors (high neutron scattering power).
• Used in precision optics (telescopes, satellites) due to its dimensional stability.

Astrophysical Role and Nucleosynthesis

• Produced by cosmic spallation of carbon and oxygen nuclei in the atmosphere or interstellar medium.
• Absent from stellar fusion products due to its nuclear instability in the triple-alpha cycle.
• Detected in certain stars as a tracer of past cosmic activity (isotope ¹⁰Be).

Fundamental Physical Issues

• Composed of light and rigid nuclei, used to study strong nuclear interactions.
• Its stable isotope ⁹Be allows scattering experiments and nuclear model tests.
• Low alpha particle absorption, useful in detector physics.
• Used as a target in neutron generators (Be + α → C + n).