Potassium, K

Potassium is a chemical element. It has the symbol K (Arabic: al qalja‎ → Latin: kalium) and atomic number 19. The name "potassium" comes from the word "potash", as potassium was first isolated from potash. Potassium is a soft silvery-white metallic alkali metal that occurs naturally bound to other elements in seawater and many minerals. It oxidizes rapidly in air and is very reactive, especially towards water. In many respects, potassium and sodium are chemically similar, although organisms in general, and animal cells in particular, treat them very differently.

Technical Data
Symbol K Melting point /°C 63.2
Atomic number 19 Boiling point /°C 765.5
No. of naturally occurring isotopes 2+1* ΔHfus/kJmol-1 2.39
Atomic weight 39.0983 ΔHvap/kJmol-1 79
Electronic configuration [Ar]4s1 ΔHf(monoatomic gas)/kJmol-1 90
Metal radius/pm 227 ΔH(dissoc)/kJmol-1 49.9
Ionic radius(6-coordinate)/pm 138 Ionization energy/kJmol-1 418.6
Eo(M+(aq)+e- →M(S))/V -2.925 *(radioactive 4°K t1/2 1.27 x 109 y)  
Density (20°C)/gcm3 0.856    
Evaporation Techniques
Temperature (oC) @Vap. Pressure Techniques Remarks
10-8 Torr 10-6 Torr 10-4 Torr Electron Beam Crucible Coil Boat
842 992 1192 Excellent Al2O3 Tungsten Tungsten Alloys with refractory metals; rapid Evaporation suggested. Spits in EB.

Evaporation Materials
P4-5000-M small pieces