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Sodium - Na

CAS:  7440-23-5
Description: Soft, silvery-white metal
Classification:Alkali Metal
Date of Discovery: 1807
Discoverer: Sir Humphrey Davy
Name Origin: English, soda; Medieval Latin, sodanum, "headache remedy"
Symbol Origin: Latin natrium, "sodium"

Atomic Number: 11
Number of Neutrons: 12
Atomic Mass: 22.9897768(6) amu
Melting Point: 97.72 ± 0.03 °C
Boiling Point: 883 °C
Density (293 K): 0.971 g/cm3
Atomic volume: 23.7 cm3/mol
Electrical resistivity: 0.139 10-6/cm Ohm Symbol
Thermal conductivity: 1.41 W/cmK
Enthalpy of atomization: 108.37 kJ/mol
Enthalpy of vaporization: 96.960 kJ/mol
Enthalpy of fusion: 2.598 kJ/mol
Specific heat capacity: 1.23 J/gK
Energy levels: 2-8-1
Electron configuration: [Ne]3s1
Crystal Structure: Cubic body centered
Atomic radius: 2.23 Å
Covalent radius: 1.54 Å
Oxidation States: +1
Electronegativity, Pauling: 0.93
Electron affinity: 0.547926 eV
First ionization energy: 5.139 eV
2nd ionization energy: 47.286 eV
3rd ionization energy: 71.641 eV
Polarizability: 24.08 10-24cm3
Isotope Natural Abundance Atomic Mass Half-life Decay Mode Spin
19Na 19.01388 0.03 s Beta Symbol+, p
20Na 20.00735 0.446 s Beta Symbol+; alpha symbol 2+
21Na 20.997655 22.48 s Beta Symbol+ 3/2+
22Na 21.994437 2.605 y Beta Symbol+; EC 3+
23Na 100. 22.9897697 Stable 3/2+
24mNa 20.2 ms IT, Beta Symbol- 1+
24Na 23.9909633 14.96 h Beta Symbol- 4+
25Na 24.989954 59.3 s Beta Symbol- 5/2+
26Na 25.99259 1.07 s Beta Symbol- 3+
27Na 26.99401 0.290 s Beta Symbol-, n 5/2+
28Na 27.9989 31 ms Beta Symbol-; Beta Symbol-, n 1+
29Na 29.0028 44 ms Beta Symbol-, n 3/2+
30Na 30.0092 50 ms Beta Symbol- 2
31Na 31.0136 7.2 ms Beta Symbol-, n (3/2-)
32Na 32.0197 13.5 ms Beta Symbol-
33Na 33.027 8.1 ms Beta Symbol-
34Na 34.035 5 ms Beta Symbol-
35Na 35.044 1.5 ms Beta Symbol-
Long recognized in compounds, sodium was first isolated by Davy in 1807 by electrolysis of caustic soda. Sodium is present in fair abundance in the sun and stars. The D lines of sodium are among the most prominent in the solar spectrum. Sodium is the sixth most abundant element on earth, comprising about 2.6% of the earth's crust; it is the most abundant of the alkali group of metals of which it is a member. The most common compound is sodium chloride, but it occurs in many other minerals, such as soda niter NaNO3, cryolite (Na3AlF6), amphibole, zeolite, sodalite [Na4Al3(SiO4)3Cl], etc. It is a very reactive element and is never found free in nature. It is now obtained commercially by the electrolysis of absolutely dry fused sodium chloride. This method is much cheaper than that of electrolyzing sodium hydroxide, as was used several years ago. Sodium is a soft, bright, silvery metal which floats on water, decomposing it with the evolution of hydrogen and the formation of the hydroxide. It may or may not ignite spontaneously on water, depending on the amount of oxide and metal exposed to the water. It normally does not ignite in air at temperatures below 115 °C. Sodium should be handled with respect, as it can be dangerous when improperly handled. Metallic sodium is vital in the manufacture of sodamide and esters, and in the preparation of organic compounds. The metal may be used to improve the structure of certain alloys, to descale metal, to purify molten metals, and as a heat transfer agent. An alloy of sodium with potassium, NaK, is also an important heat transfer agent. Sodium compounds are important to the paper, glass, soap, textile, petroleum, chemical, and metal industries. Soap is generally a sodium salt of certain fatty acids. The importance of common salt to animal nutrition has been recognized since prehistoric times. Among the many compounds that are of the greatest industrial importance are common salt (NaCl), soda ash (Na2CO3), baking soda (NaHCO3), caustic soda (NaOH), Chile saltpeter (NaNO3), di- and tri-sodium phosphates, sodium thiosulfate (Na2S2O3 · 5H2O), sodium hypochlorite (bleach, NaOCl), and borax (Na2B4O7 · 10H2O). Seventeen isotopes of sodium are recognized. Metallic sodium is priced at about $250/kg (99.95%). On a volume basis, it is the cheapest of all metals. Sodium metal should be handled with great care. It should be kept in an inert atmosphere and contact with water and other substances with which sodium reacts should be avoided.

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Sources for the information on this website include:
Lide, David R., ed. CRC Handbook of Chemistry and Physics, 78th Ed., 1997-1998.