Potassium

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Animated Potassium

History

From the English word, potash - pot ashes; Latin kalium, Arab qali, alkali. Discovered in 1807 by Davy, who obtained it from caustic potash (KOH); this was the first metal isolated by electrolysis.

Sources

The metal is the seventh most abundant and makes up about 2.4% by weight of the earth's crust. Most potassium minerals are insoluble and the metal is obtained from them only with great difficulty.

Certain minerals, however, such as sylvite, carnallite, langbeinite, and polyhalite are found in ancient lake and sea beds and form rather extensive deposits from which potassium and its salts can readily be obtained. Potash is mined in Germany, New Mexico, California, Utah, and elsewhere. Large deposits of potash, found at a depth of some 3000 ft in Saskatchewan, promise to be important in coming years.

Potassium is also found in the ocean, but is present only in relatively small amounts, compared to sodium.

Uses

The greatest demand for potash has been in its use for fertilizers. Potassium is an essential constituent for plant growth and is found in most soils.

An alloy of sodium and potassium (NaK) is used as a heat-transfer medium. Many potassium salts are of utmost importance, including the hydroxide, nitrate, carbonate, chloride, chlorate, bromide, iodide, cyanide, sulfate, chromate, and dichromate.

Isotopes

Seventeen isotopes of potassium are known. Ordinary potassium is composed of three isotopes, one of which is 40°K (0.0118%), a radioactive isotope with a half-life of 1.28 x 109 years.

General Info

AtomicNumber
19
Symbol
K
Name
Potassium

Atomic Info

Appearance
AtomicWeight
39.0983(1)
Color
8F40D4
ElectronicConfiguration
[Ar] 4s1
ElectronegativityInPauling
0.82
AtomicRadiusInPM
196
IonRadiusInPM
138 (+1)
VanDerWaalsRadiusInPM
275
IEinKJmol
419
EAinKJmol
-48
OxidationStates
1
StandardState
solid
BondingType
metallic
MeltingPoint
337
BoilingPoint
1032
Density
0.86
State
Alkali metal
DiscoveredYear
1807