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Lithium (Li), element 3
Lithium (Li) is the chemical element with atomic number 3: an alkali metal in group 1, period 2. At 25 °C it is a solid, with an atomic mass of 7 u.
Physical and chemical data
| Atomic number | 3 |
|---|---|
| Symbol | Li |
| Atomic mass | 7 u |
| Density | 0.534 g/cm³ |
| Melting point | 180.5 °C (453.65 K) |
| Boiling point | 1,341.85 °C (1,615 K) |
| Electronegativity (Pauling) | 0.98 |
| Electron configuration | [He]2s1 |
| Atomic radius (van der Waals) | 182 pm |
| Oxidation states | +1 |
| Physical state at 25 °C | solid |
| Family | alkali metal |
| Group and period | 1 / 2 |
| Discoverer and year | Johan August Arfwedson (1817) |
The discovery record belongs to Johan August Arfwedson, in 1817.
Neighbours on the table
Horizontally, one proton less lands on Helium (Z=2); one more lands on Beryllium (Z=4). Vertically, group 1 gathers relatives with similar behaviour: Hydrogen, Sodium, Potassium, Rubidium.
The story behind the name
Lithos is Greek for stone, and the name was a deliberate jab: sodium and potassium had been discovered in plant ashes, but lithium turned up in 1817 inside a Swedish mineral, petalite, analysed by young Johan Arfwedson in Berzelius's laboratory. It is the lightest metal in existence: it floats on water (while reacting with it) and would float even on oil. Two centuries later, the stone became the heart of the batteries behind phones and electric cars.
Physical and chemical data: PubChem Periodic Table (NCBI, compiling NIST and IUPAC), public domain, snapshot of 2026-07-10. Temperatures converted from kelvin; historical notes cross checked against classic chemistry references.
Last updated: · Methodology and sources