chemical element with symbol Na and atomic number 11
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Sodium is a chemical element with an atomic number of 11. Its symbol is Na (from its Latin name natrium). It is an alkali metal. Although sodium has many isotopes, most decay in a short time. Because of this, all sodium in nature (mainly found in seawater) is of the isotope 11Na23. The atomic mass of sodium is 22.9898.

Sodium, 11Na
Na (Sodium).jpg
Appearancesilvery white metallic
Standard atomic weight Ar, std(Na)22.98976928(2)[1]
Sodium in the periodic table
Hydrogen Helium
Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon
Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon
Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton
Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon
Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon
Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson


Atomic number (Z)11
Groupgroup 1: hydrogen and alkali metals
Periodperiod 3
Block  s-block
Electron configuration[Ne] 3s1
Electrons per shell2, 8, 1
Physical properties
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)
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k
at T (K) 554 617 697 802 946 1153
Atomic properties
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
Color lines in a spectral range
Spectral lines of sodium
Other properties
Natural occurrenceprimordial
Crystal structurebody-centered cubic (bcc)
Body-centered cubic crystal structure for sodium
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[2]
Molar magnetic susceptibility+16.0·10−6 cm3/mol (298 K)[3]
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)
Symbol"Na": from New Latin natrium, coined from German Natron, 'natron'
Main isotopes of sodium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct
22Na trace 2.602 y β+ 22Ne
23Na 100% stable
24Na trace 14.96 h β 24Mg
 Category: Sodium
| references
Sodium pellets in a container


Sodium is a light-weight, silver-colored metal. Sodium is soft, and because of that, someone could easily cut it with a knife. When someone cuts it, the exposed part will become white over time. It reacts with air to form sodium hydroxide and sodium carbonate. Sodium is a little less dense than water; when someone puts it in water, it floats and reacts instantly, producing hydrogen and sodium hydroxide. This reaction has a lot of heat, usually causing the hydrogen to light on fire. When this happens, sodium melts because of its low melting point. Sodium is highly reactive because it has one valence electron, which is easily removed.

Compared with other alkali metals, sodium is less reactive than potassium and more reactive than lithium.[4]

Chemical compoundsEdit

These are chemical compounds that contain sodium ions. Sodium only exists in one oxidation state: +1.

Discovery and name originsEdit

Sodium was discovered by Sir Humphrey Davy, an English scientist, in 1807. He created it by electrolyzing sodium hydroxide. Davy named the element after soda, a name for sodium hydroxide or sodium carbonate.

Use as elementEdit

Scientists can use it in the creation of organic compounds. People also use it in orange streetlights and lamps that emit ultraviolet light.

Use in compoundsEdit

Sodium compounds are used in soaps, toothpaste, baking, and antacids.

Occurrence and productionEdit

Sodium does not occur as an element in nature, because it is not stable enough. It exists only in chemical compounds. Sodium ions are found in the ocean and in the Earth's crust.

Sodium is normally made by electrolysis of sodium chloride, which is mined from the Earth's crust.

Use in organismsEdit

The human body needs sodium ions, taken in the form of sodium chloride, to live, but too much of it can cause health problems. Many organisms in the ocean depend on the concentration of sodium ions in water to survive.

Related pagesEdit


  1. "Standard Atomic Weights: Sodium". CIAAW. 2005.
  2. Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
  3. Weast, Robert (1984). CRC, Handbook of Chemistry and Physics. Boca Raton, Florida: Chemical Rubber Company Publishing. pp. E110. ISBN 0-8493-0464-4.
  4. De Leon, N. "Reactivity of Alkali Metals". Indiana University Northwest. Archived from the original on 2018-10-16. Retrieved 2007-12-07.