Type: Lesser Element
Periodic Element: (Na)
RDA: Not established; probably about 2500 mg (Diet supplies substantial excess).
Importance- To Body:
As an ion (Na
Distribution- In Body:
0.2 Approx. % of Body Mass
Widely distributed; 50% found in extra-cellular fluid, 40% in bone salts, 10% within cells; absorption is rapid and almost complete; excretion, chiefly in urine, controlled by aldosterone
Excess Effects:
Edema, Hypertension
Deficiency Effects:
Dehydration, Kidney Failure- Rare but can occur with Excessive Vomiting, Diarrhea, Sweating, or Poor Dietary Intake, Nausea, Abdominal and Muscle Cramping, Convulsions
Sources Food:
Most foods, Table Salt (1 tsp= 2000 mg); Cured Meats (Ham, etc.), Sauerkraut, Cheese
Sources Environmental/Geographic:
None listed
Supplemental information:
General properties | |||||||||||||||||||||
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Appearance | silvery white metallic | ||||||||||||||||||||
Standard atomic weight (Ar, standard) | 76928(2) 22.989 | ||||||||||||||||||||
Sodium in the periodic table | |||||||||||||||||||||
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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
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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
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Atomic properties | |||||||||||||||||||||
Oxidation states | +1, −1 |
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Electronegativity | Pauling scale: 0.93 | ||||||||||||||||||||
Ionization energies |
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Atomic radius | empirical: 186 pm | ||||||||||||||||||||
Covalent radius | 166±9 pm | ||||||||||||||||||||
Van der Waals radius | 227 pm | ||||||||||||||||||||
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Miscellanea | |||||||||||||||||||||
Crystal structure | body-centered cubic (bcc) | ||||||||||||||||||||
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 | ||||||||||||||||||||
Magnetic susceptibility | +16.0·10−6 cm3/mol (298 K) | ||||||||||||||||||||
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 | |||||||||||||||||||||
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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.