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Pronunciation | |
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Allotropes | see Allotropes of iron |
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Appearance | lustrous metallic with a grayish tinge |
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Group | group 8 |
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Period | period 4 |
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Block | d-block |
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Electron configuration | [Ar] 3d6 4s2 |
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Electrons per shell | 2, 8, 14, 2 |
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Phase at STP | solid |
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Melting point | 1811 K (1538 °C, 2800 °F) |
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Boiling point | 3134 K (2862 °C, 5182 °F) |
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Density (near r.t.) | 7.874 g/cm3 |
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when liquid (at m.p.) | 6.98 g/cm3 |
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Heat of fusion | 13.81 kJ/mol |
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Heat of vaporization | 340 kJ/mol |
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Molar heat capacity | 25.10 J/(mol·K) |
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Vapor pressure
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
1728 |
1890 |
2091 |
2346 |
2679 |
3132 |
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Oxidation states | −4, −2, −1, 0, +1,[3] +2, +3, +4, +5,[4] +6, +7[5] (an amphoteric oxide) |
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Electronegativity | Pauling scale: 1.83 |
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Ionization energies | - 1st: 762.5 kJ/mol
- 2nd: 1561.9 kJ/mol
- 3rd: 2957 kJ/mol
- (more)
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Atomic radius | empirical: 126 pm |
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Covalent radius | Low spin: 132±3 pm High spin: 152±6 pm |
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Spectral lines of iron |
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Natural occurrence | primordial |
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Crystal structure | body-centered cubic (bcc) a=286.65 pm |
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Crystal structure | face-centered cubic (fcc) between 1185–1667 K |
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Speed of sound thin rod | 5120 m/s (at r.t.) (electrolytic) |
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Thermal expansion | 11.8 µm/(m⋅K) (at 25 °C) |
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Thermal conductivity | 80.4 W/(m⋅K) |
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Electrical resistivity | 96.1 nΩ⋅m (at 20 °C) |
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Curie point | 1043 K |
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Magnetic ordering | ferromagnetic |
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Young's modulus | 211 GPa |
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Shear modulus | 82 GPa |
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Bulk modulus | 170 GPa |
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Poisson ratio | 0.29 |
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Mohs hardness | 4 |
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Vickers hardness | 608 MPa |
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Brinell hardness | 490 MPa |
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CAS Number | 7439-89-6 |
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Discovery | before 5000 BC |
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Symbol | "Fe": from Latin ferrum |
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Category: Iron | references |