Sodium
Element 11 · Alkali Metal
Sodium is the archetypal alkali metal: silvery, soft enough to cut with a knife, and violently eager to lose its single outer electron. A pea-sized lump dropped in water fizzes, melts from its own reaction heat, and can ignite the hydrogen it releases, so chemists store it under oil. Tamed as the Na+ ion, sodium is everywhere and essential — table salt flavors food, nerve cells fire using sodium gradients, and the oceans hold billions of tons of it. Industry makes soap, glass, and paper chemicals from sodium compounds.
Key facts
| Atomic number | 11 |
|---|---|
| Atomic weight | 22.990 |
| Category | Alkali Metal |
| Group / Period | 1 / 3 |
| Block | s |
| Electron configuration | 1s2 2s2 2p6 3s1 |
| Common oxidation states | +1 |
| State at STP | Solid |
| Electronegativity | 0.93 |
| Atomic radius | 190 pm |
| Density | 0.968 g/cm³ |
| Melting point | 97.72 °C |
| Boiling point | 883 °C |
Occurrence
Sodium never occurs free; it sits in seawater at about 1 percent and in vast underground salt deposits left by ancient seas. The body of an adult human contains roughly 100 grams of sodium.
Applications
Table salt (NaCl)
Soap and detergent manufacture
Sodium-vapor street lighting
Glass and paper production
Baking soda (NaHCO3)
Common compounds
- Sodium chloride (NaCl)
- Sodium hydroxide (NaOH)
- Sodium bicarbonate (NaHCO3)
- Sodium carbonate (Na2CO3)
Your neurons fire using sodium: each thought and movement begins with a rush of Na+ ions across nerve cell membranes.
Data source: IUPAC standard atomic weights 2021