Atomic number 4

Beryllium

Be
+ phase
− phase

Shells Orbitals 2s

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4 electrons in 2 shells: 2, 2.

Shells are a teaching model: an electron does not travel on a ring at a fixed distance.

Category: Alkaline earth metal
Period: 2
Group: 2
Block: s
Standard atomic weight: 9.0122(1) Da
Electron configuration: [He] 2s²
Phase at 25 °C: solid
Melting point: 1287 °C
Boiling point: 2469 °C
Density: 1.85 g/cm³
Electronegativity (Pauling): 1.57
Discovered: 1798, Louis Nicolas Vauquelin

Neighbours in the table

Li B

With its fourth electron, beryllium closes the 2s orbital: [He] 2s², with the 2p subshell still empty. That arrangement accounts for an odd step in period 2. Boron, one place to the right, has the larger nuclear charge yet the lower first ionisation energy, the energy needed to pull one electron off an atom. OpenStax traces the difference to which electron leaves: boron gives up a 2p electron, beryllium a 2s electron, and an s electron is the harder to remove.

OpenStax also notes that beryllium and magnesium, the group 2 metals with the highest ionisation energies, form compounds with some covalent character. In BeF₂ the two bonds sit on opposite sides of the beryllium atom, 180° apart, because two bonds and no lone pairs spread as far apart as they can. Gaseous BeCl₂ is described with two sp hybrid orbitals, each a mixture of one s and one p orbital. In BeH₂ the central atom falls short of an octet.

The metal is grey-white, hard and brittle, and resists oxidation in air at ordinary temperatures, partly, OpenStax says, because of a protective surface coating. Water leaves it unreacted too. Friedrich Wöhler and Antoine Bussy, working independently, first separated the metal in 1828.

Where it is found

Jefferson Lab, in PubChem’s element record, puts beryllium at 2.8 milligrams per kilogram of the crust and 5.6 × 10⁻⁶ milligrams per litre of seawater. Los Alamos counts some 30 minerals that contain it, of which bertrandite, beryl, chrysoberyl and phenacite matter most. Beryl, Be₃Al₂Si₆O₁₈, becomes emerald or aquamarine when certain impurities are present. Unlike the other alkaline earth metals, beryllium forms no carbonate or sulfate minerals.

Those gemstones led to the element. Jefferson Lab records that the Abbé Haüy recognised emerald and beryl as one mineral in 1798, and that Louis-Nicolas Vauquelin found an unknown element in them later that year. Los Alamos also dates the discovery to 1798; the CIAAW text in the same PubChem record gives 1797. The name comes from beryllos, Greek for beryl.

Utah bertrandite from Spor Mountain, with imported beryl, becomes beryllium hydroxide, which a plant in Ohio turns into metal, oxide and a beryllium-copper master alloy. Los Alamos says most metal comes from reducing beryllium fluoride with magnesium. Jefferson Lab names electrolysis of molten beryllium chloride mixed with sodium chloride.

Why it matters

Los Alamos calls beryllium one of the lightest of all metals, with one of the highest melting points among the light metals, 1287 °C. Its elastic modulus, the stiffness a material shows under load, is about a third greater than that of steel. Aircraft, missiles, spacecraft and satellites use it as a structural material. The US Geological Survey (USGS) supplies the limit: because beryllium costs more than competing materials, it goes only where its properties are needed.

Jefferson Lab lists windows for X-ray tubes among its uses. Los Alamos adds that ultra-thin foil copies integrated circuits by X-ray lithography, because the metal is relatively transparent to X-rays. Cosmic rays striking nitrogen and oxygen in the air also make beryllium: ⁷Be, with a half-life of 53.22 days, and ¹⁰Be, with 1.387 million years. These isotopes help measure rates of erosion, sedimentation and snow accumulation.

Los Alamos credits beryllium copper with springs, electrical contacts, non-sparking tools and spot-welding electrodes. Jefferson Lab assigns springs, electrodes and tools to a nickel alloy with 2 per cent beryllium, and calls the 2 per cent copper alloy beryllium bronze, used in gyroscopes.

Properties

Properties of beryllium Standard atomic weights from IUPAC/CIAAW (abridged, 2024); other values from PubChem's periodic table, kelvin converted to °C.
Property	Value	Unit	Source
Atomic number	4
Standard atomic weight	9.0122(1) Da	Da	IUPAC/CIAAW 2024
Melting point	1287 °C	°C	Los Alamos: 1287 °C
Boiling point	2469 °C	°C	Los Alamos: 2469 °C
Density	1.85 g/cm³	g/cm³
Electronegativity (Pauling)	1.57
Electron configuration	1s² 2s²
Phase at 25 °C	solid

Safety

Beryllium’s hazard lies mainly in dust, fume or mist breathed in at work. PubChem’s hazard classification gives the element the signal word Danger: fatal if inhaled, toxic if swallowed, and able to cause cancer by inhalation and allergic skin reactions. Sensitisation, the body turning allergic to beryllium, can bring on chronic beryllium disease of the lungs. The PubChem Laboratory Chemical Safety Summary and the NIOSH Pocket Guide card, from the US federal workplace-health institute, both cover the metal.

Questions

Why was beryllium once called glucinium?

Its salts taste sweet, and the old name came from glykys, the Greek word for sweet, as the CIAAW text in PubChem's element record explains. Glucinium, also spelled glucinum, stayed in use until IUPAC chose the name beryllium in 1949. Early experimenters really did taste the salts. Los Alamos and Jefferson Lab both warn that nobody should, because the element and many of its compounds are poisonous.

Is beryllium toxic?

Yes, above all as dust or fume. PubChem's hazard classification for the metal carries the signal word Danger: fatal if inhaled, toxic if swallowed, and able to cause cancer by inhalation. Breathing the dust or fume of the metal, its salts, oxides or alloys can lead to chronic beryllium disease, and alloys holding 1 to 4 per cent beryllium can cause it. The ores are not known to, although no epidemiological study of miners has been done.

Why is beryllium used in nuclear reactors?

Los Alamos lists it as a reflector or moderator in reactors, because its nuclei rarely capture thermal, or slow, neutrons: its absorption cross section for them, a measure of how likely capture is, is low. The oxide, which melts at a very high temperature, also goes into nuclear work. Beryllium struck by alpha particles gives off neutrons of its own, about 30 for every million alpha particles.

Which country produces the most beryllium?

The United States, on the US Geological Survey's estimate for 2024: 180 of the world's 360 metric tons of mined beryllium content, half the total. Brazil followed with 80, China with 77 and Mozambique with 24, while Madagascar, Rwanda and Uganda each supplied about 1. The American ore is bertrandite from Spor Mountain, Utah, where proven and probable reserves hold about 19,000 tons of beryllium.