A neutral atom of sodium has 11 protons, 11 electrons and 12 neutrons. Sodium has a melting point of about 208 degrees Fahrenheit, and a boiling point of about 1,620 degrees Fahrenheit. Sir Humphrey Davy isolated sodium and identified it as an element in 1807. Sodium is in group 1 of the periodic table, which means it is an alkali metal. Seventeen isotopes of sodium have been discovered (an isotope is a form of an element that has the same number of protons but a different number of neutrons).
As an alkali metal, sodium has certain properties that make it different from other metals. Most importantly, sodium is extremely reactive; sodium is never in its pure state in nature because it can easily react with any other element. In comparison to other alkali metals, sodium is one of the least chemically-active alkali metals. Reactions with water cause pure sodium to become flammable, and reactions with air also have the possibility of igniting.
Isolated, pure elemental sodium is extremely rare because of sodium's ease with which it combines with other elements, but pure sodium is soft and silvery. However, almost all naturally-occurring sodium is found in compounds, which is when atoms join together to form new substances. Sodium is also commonly found in the ocean as an ion, which is an atom that has lost or gained an electron and now has a charge, as opposed to being neutral. Ionic sodium is stable and not nearly as chemically reactive as neutral sodium.
Sodium compounds are both essential to living organisms and also used practically by humans. Sodium chlorde (NaCl), common table salt, is essential to cell function in living organisms as it helps produce electrolytes, which are essential for blood. Sodium also appears in several different industrial compounds, such as baking soda (NaHCO3) and bleach (NaOCl), as well as being used in alloys (metals mixed from different elements) because it is efficient at transferring heat.