Sodium
Appearancesilvery white metallic
Standard atomic weight Ar, std(Na)22.98976928(2)
Atomic number (Z)11
Groupgroup 1: H and alkali metals
Periodperiod 3
Blocks-block
Element category  Alkali metal
Electron configuration[Ne] 3s1
Electrons per shell
2, 8, 1
Phase at STPsolid
Melting point370.944 K ​(97.794 °C, ​208.029 °F)
Boiling point1156.090 K ​(882.940 °C, ​1621.292 °F)
Density (near r.t.)0.968 g/cm3
when liquid (at m.p.)0.927 g/cm3
Critical point2573 K, 35 MPa (extrapolated)
Heat of fusion2.60 kJ/mol
Heat of vaporization97.42 kJ/mol
Molar heat capacity28.230 J/(mol·K)
Oxidation states−1, +1 (a strongly basic oxide)
ElectronegativityPauling scale: 0.93
Ionization energies
  • 1st: 495.8 kJ/mol
  • 2nd: 4562 kJ/mol
  • 3rd: 6910.3 kJ/mol
  • (more)
Atomic radiusempirical: 186 pm
Covalent radius166±9 pm
Van der Waals radius227 pm
Natural occurrenceprimordial
Speed of sound thin rod3200 m/s (at 20 °C)
Thermal expansion71 µm/(m·K) (at 25 °C)
Thermal conductivity142 W/(m·K)
Electrical resistivity47.7 nΩ·m (at 20 °C)
Magnetic orderingparamagnetic
Magnetic susceptibility+16.0·10−6 cm3/mol (298 K)
Young's modulus10 GPa
Shear modulus3.3 GPa
Bulk modulus6.3 GPa
Mohs hardness0.5
Brinell hardness0.69 MPa
CAS Number7440-23-5
Discovery and first isolationHumphry Davy (1807)