Atomic Number: 11
Atomic Mass: 22.98977 amu (atomic mass units)
Melting Point: 97.72 C (370.87 K, 207.9 F)
Boiling Point: 883 C (1156 K, 1621 F)
Number of Protons: 11
Number of Electrons: 11
Number of Neutrons: 12
Group Name: Alkali Metal
Crystal Structure: Cubic
Density @ 293 K: 0.971 grams per cubic centimeter
The British scientist Sir Humphrey Davy discovered this very reactive alkali metal in 1807. The name of the element comes from soda (Na2CO3), as well as from the Medieval Latin word “sodanum” which meant headache remedy. The symbol Na comes from the Latin for the compound sodium carbonate “natrium”.
Sodium metal is an extremely soft metal, which is easily cut with a knife. The sodium atom has only one electron in its outer shell, which it will easily give up to an atom of another element to form an ionic bond. When brought into contact with water sodium metal will react violently, producing hydrogen, which can ignite. To prevent it reacting with water vapor in the air the pure metal is normally stored under a mineral oil. It is not the most reactive of the alkali metals as potassium, rubidium and cesium are all more reactive than sodium.
Because it is so reactive, sodium cannot exist in nature in its metallic state. It forms a number of important rock forming minerals such as plagioclase and oligoclase. It is the sixth most abundant element found on earth making up 2.6% of the earth’s crust with an estimated crustal abundance of 2.36 grams per kilogram. Within the earth’s oceans, it has an estimated abundance of 1.08 grams per liter.
The element has only one naturally occurring isotope, which is sodium-23. Sodium-23 is a stable isotope. A number of unstable isotopes of sodium have been produced with mass numbers that range from 18 to 35. Sodium-19 has the shortest half-life at less than 40 nanoseconds it decays by proton emission. The isotope with the longest half-life is sodium-22 at 2.6019 years it decays by electron capture.
Sodium is an essential element for life. It is the most common extra-cellular cation within the human body. This ion has a number of biological functions including assisting in the transmission of nerve impulses.
Sodium forms a number of common useful compounds such as salt (NaCl), caustic soda (NaOH), baking soda (NaHCO3) and borax (Na2B4O7.10H2O).
Industry uses sodium in the production of sodium peroxide, sodium hydride, sodamide, sodium cyanide and titanium. The yellow color seen in many street lamps is due to the presence of sodium vapor within the bulbs. The nuclear power industry uses liquid sodium as a coolant for reactors.
Los Alamos National Laboratory Chemistry Division
Jefferson Laboratories Science Education