Supplier Data - Potassium (K) (Goodfellow)

Background

Potassium (K) was discovered in 1807 by Sir Humphrey Davy in London.

Abundance and Extraction

Potassium is a soft, silvery coloured metal, which like other members of the alkali group of metals, is extremely reactive.

As with other members of the group, Potassium can be prepared by electrolysis of the fused halide.

Potassium is one of the more common alkali metals, there being 26000 ppm in the earth's crust, the main source being potassium chloride.

Occurrence

Potassium does not occur naturally.

Applications

Potassium has limited use as the pure metal, although it can be used with sodium as a coolant in liquid metal reactors.

It is more commonly used as a salt; for example potassium bromide (KBr), which is used in photography, and potassium carbonate (K2CO3) which has applications in the areas of fluxes, pharmaceuticals and soaps. One of the most important uses of potassium salts is as fertilisers.

Potassium salts are commonly used as fertilisers. Image credit: Jen Watson/Shutterstock

Potassium salts are commonly used as fertilisers. Image credit: Jen Watson/Shutterstock

Potassium and the Human Body

Potassium is an essential element for all living beings and, on average, a human being contains approximately 140 gm, the majority of which is present in muscle tissue.

Key Properties

The key properties of Potassium are tabulated below.

Table 1. Key properties

Atomic Properties
Atomic number 19
Atomic radius - Goldschmidt ( nm ) 0.238
Atomic weight ( amu ) 39.0983
Crystal structure Body centred cubic
Electronic structure Ar 4s1
Photo-electric work function ( eV ) 2.2
Thermal neutron absorption cross-section ( Barns ) 1.8
Valences shown 1
Ionisation potential No. eV
1 4.34
2 31.6
3 45.7
4 60.9
5 82.7
6 100
Natural Isotope Distribution Mass No. %
39 93.26
40 0.01
41 6.73
Electrical Properties
Electrical resistivity @ 20 °C ( µOhm.cm ) 6.8
Temperature coefficient @ 0-100 °C ( K-1 ) 0.0057
Mechanical Properties
Material condition Polycrystalline @ -190 °C
Bulk modulus ( GPa ) 3.1
Hardness – Mohs 0.5
Poisson’s ratio 0.35
Tensile modulus ( GPa ) 3.53
Physical Properties
Boiling point (°C ) 760
Density @ 20 °C ( g.cm-3 ) 0.86
Melting point (°C ) 63.25
Thermal Properties
Coefficient of thermal expansion @ 0-100 °C ( x10-6 K-1 ) 83
Latent heat of evaporation ( J.g-1 ) 2033
Latent heat of fusion ( J g-1 ) 61
Specific heat @ 25 °C ( J.K-1.kg-1 ) 753
Thermal conductivity @ 0-100 °C ( W.m-1.K-1 ) 102.5

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