Potassium

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Potassium is a soft, waxy, silvery reactive metal that is never found unbound in nature; an element (symbol K) with an atomic number of 19 and atomic weight of 39.0983. The symbol is derived from the Latin kalium.

 

General
Name, symbol, number potassium, K, 19
Chemical series alkali metals
Group, period, block 1, 4, s
Appearance silvery white
Standard atomic weight 39.0983(1)g·mol-1
Electron configuration [Ar] 4s1
Electrons per shell 2, 8, 8, 1
Physical properties
Phase solid
Density (near r.t.) 0.89 g·cm-3
Liquid density at m.p. 0.828 g·cm-3
Melting point 336.53 K
(63.38 °C, 146.08 °F)
Boiling point 1032 K
(759 °C, 1398 °F)
Triple point 336.35 K (63°C),  kPa
Atomic properties
Crystal structure cubic body centered
Oxidation states 1
(strongly basic oxide)
Electronegativity 0.82 (Pauling scale)
Ionization energies
(more)
1st: 418.8 kJ·mol-1
2nd: 3052 kJ·mol-1
3rd: 4420 kJ·mol-1
Atomic radius 220 pm
Atomic radius (calc.) 243 pm
Covalent radius 196 pm
Van der Waals radius 275 pm
Miscellaneous
Magnetic ordering paramagnetic
Thermal conductivity (300 K) 102.5 W·m-1·K-1
Thermal expansion (25 °C) 83.3 µm·m-1·K-1
Speed of sound (thin rod) (20 °C) 2000 m/s
Young's modulus 3.53 GPa
Shear modulus 1.3 GPa
Bulk modulus 3.1 GPa
Mohs hardness 0.4
Brinell hardness 0.363 MPa
CAS registry number 7440-09-7

 

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