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Potassium 19K39.102
Isolated in 1807 by Sir Humphry Davy at London, England.
[English: potash; Latin: kalium]
French: potassium
German: Kalium
Italian: potassio
Spanish: potasio
Description: Potassium
is a soft white metal which is very silvery when first cut but oxidizes rapidly
in air. It reacts violently with water. Potassium is obtained from the reaction
of sodium metal with potassium chloride. The metal itself is little used, but
potassium compounds are important in fertilizers, chemicals and glass.
Materials properties
| Density: |
862 kg/m-3 [293 K]; 828 [liquid at m.p.] |
| Melting point: |
336.80 °K |
| Boiling point: |
1047 °K |
| Molar volume: |
45.36 cm3 |
| Thermal conductivity: |
102.4 [300 K] Wm-1K-1 |
| Coefficient of linear thermal expansion: |
83 x 10-6 K-1 |
| Electrical resistivity: |
6.15 x 10-8 [273 K] Wm |
| Mass magnetic susceptibility: |
+6.7 x 10-9(s) kg-1m3 |
| Young's modulus: |
3.53 GPa [83 K] |
| Rigidity modulus: |
1.30 GPa |
| Bulk modulus: |
n.a. |
| Poisson's ratio: |
0.34 GPa [83 K] |
| Radii: |
K+ 133; atomic 227; covalent 203; van der Waals 231 |
| Electronegativity: |
0.82 (Pauling); 0.91 (Allred); 2.42 eV (absolute) |
| Effective nuclear charge: |
2.20 (Slater); 3.50 (Clementi); 4.58 (Froese-Fischer) |
| Number of Isotopes (incl. nuclear isomers): |
18 |
| Issotope mass range: |
35 -> 51 |
Biological data
| Biological role: |
Essential to all living things. |
| Toxicity |
|
| Toxic intake: |
KCl = c. 4 g |
| Lethal intake: |
LD50(chloride, oral, rat) = 2600 mg kg-1 |
| Hazards: |
The toxicity of potassium compounds is almost always that of the anion, not of the K+. However although, KCl is often used as a nutrient or dietary supplement, there are rare cases of excess ingestion by humans proving fatal.
|
| Level in humans |
|
| Blood: |
1620 mg dm-3 |
| Bone: |
2100 p.p.m. |
| Liver: |
16 000 p.p.m. |
| Muscle: |
16 000 p.p.m. |
| Daily dietary intake : |
1400 - 7400 mg |
| Total mass of element in average [70 kg] person: |
140 g |
Crystal data
| Crystal structure, (cell dimentions / pm), space group |
b.c.c. (a=533.4) Im3m |
| X-ray diffraction: mass absorption coefficients (µ/ρ)/cm2g-1 : |
CuKα 143 MoKα 15.8 |
| Neutron scattering length, b/10-12cm: |
0.367 |
| Thermal neutron capture cross-section, σa/barns : |
2.1 |
Geological data
| Minerals: |
Potassium occurs in many minerals. |
| Mineral |
Formula |
Density |
Hardness |
Crystal apperance |
| Alunite |
KAL3(SO4)2(OH)6 |
2.69 |
3.5 - 4 |
rhom., vit. white/grey |
| Carnallite |
KCl.MgCl2.6H2O |
1.602 |
2.5 |
orth., greasy colorless-red |
| Orthoclase* |
KAlSi3O8 |
2.563 |
6 - 6.5 |
mon., vit. colorless/white |
| Sylvite |
KCl |
1.993 |
2 |
cub., vit. colorless/white |
*Mined on large scale for porcelain, ceramics and glass.
| Chief ore: |
sylvite, carnalite, alunite |
| World production: |
200 tonnes/year (potassium metal); 51 x 106 (potassium salts) tonnes/year |
| Main mining areas: |
Germany, Spain, Canada, USA, Italy |
| Reserves: |
vast, > 1 x 1010 tonnes |
| Specimen: |
available as chunks (in mineral oil) or ingots (in ampoules). Warning! |
| Abundances |
|
| Sun: |
1.45 x 105 (relative to H = 1 x 1023) |
| Earth's crust: |
21000 p.p.m. |
| Residence time: |
5 x 106 years |
| Classification: |
accumulating |
| Oxidation state: |
I |
Other sizes and specifications on request
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