Potassium pearls (in paraffin oil, ~5 mm each) |
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Appearance | silvery gray |
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| 39.0983(1)[1] |
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Group | group 1: hydrogen and alkali metals |
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Period | period 4 |
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Block | s-block |
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Electron configuration | [Ar] 4s1 |
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Electrons per shell | 2, 8, 8, 1 |
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Phase at STP | solid |
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Melting point | 336.7 K (63.5 °C, 146.3 °F) |
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Boiling point | 1032 K (759 °C, 1398 °F) |
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Density (near r.t.) | 0.862 g/cm3 |
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when liquid (at m.p.) | 0.828 g/cm3 |
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Critical point | 2223 K, 16 MPa[2] |
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Heat of fusion | 2.33 kJ/mol |
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Heat of vaporization | 76.9 kJ/mol |
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Molar heat capacity | 29.6 J/(mol·K) |
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Oxidation states | −1, +1 (a strongly basic oxide) |
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Electronegativity | Pauling scale: 0.82 |
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Ionization energies | - 1st: 418.8 kJ/mol
- 2nd: 3052 kJ/mol
- 3rd: 4420 kJ/mol
- (more)
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Atomic radius | empirical: 227 pm |
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Covalent radius | 203±12 pm |
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Van der Waals radius | 275 pm |
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Spectral lines of potassium |
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Natural occurrence | primordial |
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Crystal structure | body-centered cubic (bcc) |
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Speed of sound thin rod | 2000 m/s (at 20 °C) |
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Thermal expansion | 83.3 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 102.5 W/(m⋅K) |
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Electrical resistivity | 72 nΩ⋅m (at 20 °C) |
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Magnetic ordering | paramagnetic[3] |
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Molar magnetic susceptibility | +20.8·10−6 cm3/mol (298 K)[4] |
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Young's modulus | 3.53 GPa |
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Shear modulus | 1.3 GPa |
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Bulk modulus | 3.1 GPa |
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Mohs hardness | 0.4 |
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Brinell hardness | 0.363 MPa |
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CAS Number | 7440-09-7 |
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Discovery and first isolation | Humphry Davy (1807) |
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Symbol | "K": from New Latin kalium |
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Main isotopes |
Decay |
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abundance |
half-life (t1/2) |
mode |
product |
39K |
93.3% |
stable |
40K |
0.0120% |
1.248×109 y |
β− |
40Ca |
ε |
40Ar |
β+ |
40Ar |
41K |
6.73% |
stable |
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Category: Potassium | references |