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Oxidation & Electrons | Appearance & Characteristics Reactions | Compounds | Radius | Conductivity Abundance & Isotopes 
Scrap iron and steel - with surface iron oxide - for recycling. |
General:
| Name: Iron | Symbol: Fe |
| Type: Transition Metal | Atomic weight: 55.847 |
| Density @ 293 K: 7.87 g/cm3 | Atomic volume: 7.1 cm3/mol |
| Discovered: Iron has been known since ancient times. The origin of the chemical symbol Fe is from the Latin word 'ferrum', meaning iron. The first iron used by humans is likely to have been sourced from fallen meteorites. Most objects that fall to earth from space are stony, but a small proportion are "iron meteorites" with iron contents of over 90 percent. | |
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An Iron meteorite: Meteorites such as this one are believed to have been our ancestors' first source of iron. This is one fragment of the Sikhote-Alin meteorite. It is about 15 cm across and is composed of approximately 93 % iron, 6 % nickel and 1 % other elements. The photograph shows the original meteorite surface, melted into thumb-print shapes during its flight through our atmosphere. Photo by Carl Allen, NASA JSC photo S94-43472 |
States
| State (s, l, g): solid | |
| Melting point: 1808.2 K (1535.1 oC) | Boiling point: 3023 K (2750 oC) |
Energies
| Specific heat capacity: 0.44 J g-1 K-1 | Heat of atomization: 415 kJ mol-1 |
| Heat of fusion: 13.80 kJ mol-1 | Heat of vaporization (sublimation): 349.60 kJ mol-1 |
| 1st ionization energy: 759.3 kJ mol-1 | 2nd ionization energy: 1561.1 kJ mol-1 |
| 3rd ionization energy: 2957.3 kJ mol-1 | Electron affinity: 15.7 kJ mol-1 |
Oxidation & Electrons
| Shells: 2,8,14,2 | Electron configuration: [Ar] 3d6 4s2 |
| Minimum oxidation number: -2 | Maximum oxidation number: 6 |
| Min. common oxidation no.: 0 | Max. common oxidation no.: 3 |
| Electronegativity (Pauling Scale): 1.9 | Polarizability volume: 8.4 Å3 |
Appearance & Characteristics
| Structure: bcc: body-centered cubic | Color: gray |
| Harmful Effects: Iron is considered to be non-toxic. | Hardness: 4.0 mohs |
| Characteristics: Iron is a ductile, gray, relatively soft metal and is a moderately good conductor of heat and electricity. It is attracted by magnets and can be readily magnetized. The pure metal is chemically very reactive and rusts readily in moist air, forming red-brown oxides. There are three allotropic forms of iron, known as alpha, gamma, and delta. Alpha iron, also known as ferrite, is the stable form of iron at normal temperatures. | |
| Uses: Iron is the cheapest and most important of all metals - important in the sense that iron is overwhelmingly the most commonly used metal, accounting for 95 percent of worldwide metal production. Iron is used to manufacture steel and other alloys important in construction and manufacturing. Iron is also vital in the functioning of living organisms, transporting oxygen in blood via the hemoglobin molecule. | |
Reactions
| Reaction with air: mild, ⇒ Fe3O4 | Reaction with 6 M HCl: vigorous, ⇒ H2, FeCl2 |
| Reaction with 3 M HNO3: passivated | Reaction with 6 M NaOH: |
Compounds
| Oxide(s): FeO, Fe2O3 (hematite), Fe3O4 (magnetite), | Chloride(s): FeCl2, FeCl3 |
| Hydride(s): none |
Radius
| Atomic radius: 140 pm | Ionic radius (1+ ion): pm |
| Ionic radius (2+ ion): 77 pm | Ionic radius (3+ ion): 63 pm |
| Ionic radius (2- ion): pm | Ionic radius (1- ion): pm |
Conductivity
| Thermal conductivity: 80.4 W m-1 K-1 | Electrical conductivity: 0.112 x 106 S cm-1 |
Abundance & Isotopes
| Abundance earth's crust: 6.3 % weight, 2.3 % by moles | |
| Abundance solar system: 1000 ppm by weight, 30 ppm by moles | |
| Cost, pure: 6.7 $/100g | |
| Cost, bulk: 0.021 $/100g | |
| Source: Iron is not found free in nature but is found in iron ores such as hematite (Fe2O3), magnetite (Fe3O4) and taconite. Commercially, iron is produced in a furnace at temperatures of about 2,000 oC by the reduction of hematite or magnetite with carbon. | |
| Isotopes: Iron has 24 isotopes whose half-lives are known, with mass numbers 46 to 69. Of these, four are stable, 54Fe, 56Fe, 57Fe and 58Fe. Over 91.7% of of naturally occurring iron is in the form of 56Fe. | |
