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Beryllium

Element 4 · Alkaline earth metal

Specimen

Atomic number
4
Atomic mass
9.0122
State at room temperature
Solid
Melting point
1,287 °C
Boiling point
2,471 °C
Density
1.85 g/cm³
Discovered
1798

Atomic mass from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Harmful. Food contains small amounts of beryllium. Breathing beryllium dust can cause lung disease and lung cancer. In animal studies, researchers found that beryllium in food or water may cause stomach damage. IARC classes beryllium as a cause of cancer in humans. 3

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The atom

Be
ShellElectrons
1 (K) 2
2 (L) outermost 2
Total4

Configuration [He] 2s²

2s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 4 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the He core, with one arrow per electron.

Related elements

Group 2
Mg Magnesium Ca Calcium Sr Strontium Ba Barium Ra Radium

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Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Abridged Standard Atomic Weights 2024 .

    The atomic mass shown for the 84 elements that have a standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    Agency for Toxic Substances and Disease Registry (ATSDR), 2023. ToxFAQs for Beryllium .

    • There are small amounts of beryllium in food ... Breathing in beryllium can lead to lung disease and lung cancer ... Studies in animals have shown that eating or drinking beryllium may cause stomach damage
    • The International Agency for Research on Cancer (IARC) has classified beryllium as carcinogenic to humans
  4. 4

    National Institute of Standards and Technology (NIST), 2026. Atomic Weights and Isotopic Compositions for All Elements .

    Isotopic composition of each element; the most abundant isotope sets the neutron count in the nucleus view.