Atomic number:19

Group numbers:1

Period:4

Electronic configuration:[Ar] 4s¹

Formal oxidation number:+1

Electronegativities:0.82

Atomic radius / pm:227.2

Relative atomic mass:39.0983 ± 0.0001

 

Potassium was discovered by Sir Humphry Davy (GB) in 1807. The origin of the name comes from the Arabic word qali meaning alkali (the origin of the symbol K comes from the Latin word kalium). It is a soft, waxy, silver-white metal. Fresh surfaces have a silvery sheen. Potassium quickly forms dull oxide coating on exposure to air. It reacts strongly with water and gives off a flammable gas. It also reacts violently with oxidants. Potasium occurs only in compounds. Potassium is found in minerals like carnallite [(KMgCl3).6H2O] and sylvite (KCl). Pure metal is produced by the reaction of hot potassium chloride and sodium vapours in a special retort. Pottasium is used as potash in making glass and soap and as saltpetre, potassium nitrate (KNO3) to make explosives and to colour fireworks in mauve. Potassium ions are vital to function of nerve and muscle tissues.

Density / g dm^-3:862 (293 K)

 828 (m.p.)

Molar volume / cm³mol^-1:45.36 (293 K)

 47.22 (m.p.)

Electrical resistivity / μΩcm:6.15 (20 °C)

Thermal conductivity / W m^-1K^-1:102

Melting point / °C:63.28

Boiling point / °C:759

Heat of fusion / kJ mol^-1:2.4

Heat of vaporization / kJ mol^-1:79.1

Heat of atomization / kJ mol^-1:90.14

1st ionization energy / kJ mol^-1:418.81

2nd ionization energy / kJ mol^-1:3051.85

3rd ionization energy / kJ mol^-1:4419.64

in the atmosphere / ppm:-

in the Earth's crust / ppm:9100

in the oceans / ppm:380