An Overview about the Chemical Element Potassium


Symbol: K

Atomic Number: 19

Atomic Mass: 39.0983 amu (atomic mass units)

Melting Point: 63.65 C (336.8 K, 146.57 F)

Boiling Point: 774.0 C (1047.15 K, 1425.2 F)

Number of Protons: 19

Number of Electrons: 19

Number of Neutrons: 20

Classification: Metal

Group Name: Alkali Metal

Crystal Structure: Cubic

Density @ 293 K: 0.862 grams per cubic centimeter

Color: silver

The element potassium was discovered by Sir Humphry Davy in 1807 using electrolysis of molten caustic potash (KOH). The name is derived from the English word “potash”. The elements symbol K came from the Latin word for alkali “kalium”.

Potassium metal is very soft and can be cut easily with a knife. It is a highly reactive metal and will react violently with water producing hydrogen gas, potassium hydroxide (KOH) and heat. The heat produced in this reaction will ignite the hydrogen. It will also react with oxygen to producing potassium superoxide (KO2). To prevent any reactions with oxygen or water vapor in the atmosphere pure potassium metal is stored in mineral oil.

There are three naturally occurring isotopes of potassium. Two of these isotopes are stable while the third, potassium-40, has an extremely long half life. The isotopes are found in the following abundances: potassium-39 (93.2581%), potassium-41 (6.7302%) and potassium-40(0.0117%). Other unstable isotopes of potassium have mass numbers ranging from 32 to 64.

Potassium is the eighth most common element to be found in the earth’s crust. It is estimated that potassium accounts for 2.1% of the earth’s crust. It never found in its free state but can be found in a number of mineral ores such as sylvite, carnallite, langbeinite and polyhalite. The mineral ores containing potassium are often found in deposits which were laid down in ancient lakes or seas. Another source of potassium is caustic potash. There are caustic potash mines in Germany, New Mexico, California and Utah.

An alloy of sodium and potassium is used in the nuclear power industry as a heat transfer medium in some nuclear reactors. Most uses of potassium involve its compounds.

* Potassium chloride (KCl) is used to as a salt substitute. It is also used in fertilizers and to make other chemicals.

* Potassium carbonate (KHCO3) which is also known as pearl ash can be used to make soaps. It is also used in the manufacture of some kinds of glass.

* Potassium hydroxide (KOH) is also used to make soaps as well as detergents and drain cleaners.

* Potassium superoxide (KO2) is used in respiratory equipment as it can produce oxygen from carbon dioxide and water vapor.

* Potassium nitrate (KNO3) is also known as saltpetre. It is used in fertilizers as well as in match-heads and fireworks.