"Natrium" redirects here. For other uses, see Natrium (disambiguation).
Sodium, 11Na
Na (Sodium)
General properties
Appearance silvery white metallic
Standard atomic weight (Ar, standard) 22.98976928(2)[1]
neon ← sodium → magnesium
Atomic number (Z) 11
Group group 1 (alkali metals)
Period period 3
Element category alkali metal
Block s-block
Electron configuration [Ne] 3s1
Electrons per shell
2, 8, 1
Physical properties
Phase at STP solid
Melting point 370.944 K (97.794 °C, 208.029 °F)
Boiling point 1156.090 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 point 2573 K, 35 MPa (extrapolated)
Heat of fusion 2.60 kJ/mol
Heat of vaporization 97.42 kJ/mol
Molar heat capacity 28.230 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)
Electronegativity Pauling scale: 0.93
Ionization energies
1st: 495.8 kJ/mol
2nd: 4562 kJ/mol
3rd: 6910.3 kJ/mol
(more)
Atomic radius empirical: 186 pm
Covalent radius 166±9 pm
Van der Waals radius 227 pm
Color lines in a spectral range
Spectral lines
Miscellanea
Crystal structure body-centered cubic (bcc) Body-centered cubic crystal structure for sodium
Speed of sound thin rod 3200 m/s (at 20 °C)
Thermal expansion 71 µm/(m·K) (at 25 °C)
Thermal conductivity 142 W/(m·K)
Electrical resistivity 47.7 nΩ·m (at 20 °C)
Magnetic ordering paramagnetic[2]
Magnetic susceptibility +16.0·10−6 cm3/mol (298 K)[3]
Young's modulus 10 GPa
Shear modulus 3.3 GPa
Bulk modulus 6.3 GPa
Mohs hardness 0.5
Brinell hardness 0.69 MPa
CAS Number 7440-23-5
History
Discovery and first isolation Humphry Davy (1807)
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
Sodium is a chemical element with symbol Na (from Latin natrium) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table, because it has a single electron in its outer shell that it readily donates, creating a positively charged ion—the Na+ cation. Its only stable isotope is 23Na. The free metal does not occur in nature, but must be prepared from compounds. Sodium is the sixth most abundant element in the Earth's crust, and exists in numerous minerals such as feldspars, sodalite, and rock salt (NaCl). Many salts of sodium are highly water-soluble: sodium ions have been leached by the action of water from the Earth's minerals over eons, and thus sodium and chlorine are the most common dissolved elements by weight in the oceans.
Sodium was first isolated by Humphry Davy in 1807 by the electrolysis of sodium hydroxide. Among many other useful sodium compounds, sodium hydroxide (lye) is used in soap manufacture, and sodium chloride (edible salt) is a de-icing agent and a nutrient for animals including humans.
Sodium is an essential element for all animals and some plants. Sodium ions are the major cation in the extracellular fluid (ECF) and as such are the major contributor to the ECF osmotic pressure and ECF compartment volume. Loss of water from the ECF compartment increases the sodium concentration, a condition called hypernatremia. Isotonic loss of water and sodium from the ECF compartment decreases the size of that compartment in a condition called ECF hypovolemia.
By means of the sodium-potassium pump, living human cells pump three sodium ions out of the cell in exchange for two potassium ions pumped in; comparing ion concentrations across the cell membrane, inside to outside, potassium measures about 40:1, and sodium, about 1:10. In nerve cells, the electrical charge across the cell membrane enables transmission of the nerve impulse—an action potential—when the charge is dissipated; sodium plays a key role in that activity.
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