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Lithium

Element 3 · Alkali metal

Specimen

Atomic number
3
Atomic mass
6.94
State at room temperature
Solid
Melting point
180.5 °C
Boiling point
1,342 °C
Density
0.534 g/cm³
Discovered
1817

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

Can I eat it?

In food and water
Harmful. Lithium is in drinking water and some foods. The US EPA uses a health reference level of 10 µg per liter of water. It based this level on harm in patients who take lithium as a medicine. 3

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The atom

Li
ShellElectrons
1 (K) 2
2 (L) outermost 1
Total3

Configuration [He] 2s¹

2s ↑
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 3 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 1
H Hydrogen Na Sodium K Potassium Rb Rubidium Cs Caesium Fr Francium

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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

    U.S. Environmental Protection Agency, Office of Water, 2023. Technical Fact Sheet: Lithium in Drinking Water (UCMR 5) , Pages 1 and 2.

    • Lithium is likely present in a variety of foods ... Health Reference Level (HRL) of 10 µg/L is based on the p-RfD
    • The provisional value for lithium is based on adverse effects observed in patients administered lithium therapeutically
  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.