FACOLTÀ CHIMICA DI TECNOLOGIA IN SPLIT
TAVOLA PERIODICA DEGLI ELEMENTI versione 1.7
K
Inglesi: Potassium
Francesi: Potassium
Croato: Kalij
Tedesco: Kalium
Italiano: Potassio
Numero atomico: 19
Gruppo: 1
Periodo: 4
Stato di aggregazione (20 °C): solido
Potassium was discovered by Sir Humphry Davy (England) 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 soft, waxy, silver-white metal. Fresh surface has silvery sheen. Quickly forms dull oxide coating on exposure to air. Reacts strongly with water. Reacts with water to give off flammable gas. Reacts violently with oxidants. Occurs only in compounds.
Configurazione elettronica: [Ar] 4s1
Massa atomica relativa: 39.0983(1)
Numeri di ossidazione: +1
Elettronegatività: 0.82
Conducibilità termica: 102 W/(m K)
Resistività Elettrica (20 °C): 6.15 μΩcm
Raggio atomico: 227.2 pm
Densità (g/dm3): 862 (293 K)
828 (m.p.)
Volume atomico (cm3/mol): 45.36 (293 K)
47.22 (m.p.)
Temperatura di fusione: 63.38 °C
Temperatura di ebollizione: 759 °C
Critica temperatura: 1950 °C
Calore di fusione: 2.4 kJ/mol
Calore di vaporizzazione: 79.1 kJ/mol
Calore di atomizzazione: 90.14 kJ/mol
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. Used as potash in making glass and soap. Also as saltpetre, potassium nitrate (KNO3) to make explosives and to colour fireworks in mauve. Vital to function of nerve and muscle tissues. The price of 90.2 % pure potassium metal is 90.20 € for 5 g.
18Ar <= 19K => 20Ca
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Last modified:
29.03.2003
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