Sodium is a highly reactive chemical element categorized under the alkali metals group in the periodic table. Represented by the symbol ‘Na’, it is the sixth most common element on Earth. Sodium plays a vital role in human health, regulating blood pressure and volume, and aiding in muscle and nerve function. It is most commonly recognized in its compound form – sodium chloride, which is common table salt. However, it is also found in many other substances like baking soda (sodium bicarbonate) and soda ash (sodium carbonate). Despite its crucial roles, excessive sodium intake can lead to health issues like hypertension.
Sodium is a chemical element with the 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. Its only stable isotope is 23Na. The free metal does not occur in nature and 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 halite (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 | ||||||||||||||||||||||||||
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Appearance | silvery white metallic | |||||||||||||||||||||||||
Standard atomic weight Ar°(Na) | ||||||||||||||||||||||||||
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Sodium in the periodic table | ||||||||||||||||||||||||||
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Atomic number (Z) | 11 | |||||||||||||||||||||||||
Group | group 1: hydrogen and alkali metals | |||||||||||||||||||||||||
Period | period 3 | |||||||||||||||||||||||||
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
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Atomic properties | ||||||||||||||||||||||||||
Oxidation states | −1, 0, +1 (a strongly basic oxide) | |||||||||||||||||||||||||
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 | |||||||||||||||||||||||||
Spectral lines of sodium | ||||||||||||||||||||||||||
Other properties | ||||||||||||||||||||||||||
Natural occurrence | primordial | |||||||||||||||||||||||||
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 | |||||||||||||||||||||||||
Molar 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) | |||||||||||||||||||||||||
Symbol | "Na": from New Latin natrium, coined from German Natron, 'natron' | |||||||||||||||||||||||||
Isotopes of sodium | ||||||||||||||||||||||||||
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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.[citation needed] 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.