Potassium
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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