Iron
transition metalProperties
| Property | Value |
|---|---|
| Atomic Mass | 55.845 amu |
| Category | transition metal |
| Group | 8 |
| Period | 4 |
| Electron Configuration | 1s2 2s2 2p6 3s2 3p6 3d6 4s2 |
| Electronegativity | 1.83 (Pauling) |
| Oxidation States | 3, 2 |
| Melting Point | 1811 K (1537.8 °C) |
| Boiling Point | 3134 K (2860.8 °C) |
| Density | 7.874 g/cm³ |
About Iron
Iron is where stellar nucleosynthesis hits its energetic dead end — fusion past Fe-56 costs energy instead of releasing it, which is why iron piles up in supernova remnants and why every planet with a core has one made mostly of iron. Down here, the chemistry that matters all comes from one fact: Fe(II) and Fe(III) sit close enough in potential (E° = +0.77 V) that the Fe²⁺/Fe³⁺ couple can be cycled by mild reductants and oxidants. Hemoglobin uses it to grab and release O₂ four billion times in a red cell's lifetime. Cytochromes use it to shuttle electrons down the mitochondrial chain. Fenton chemistry uses it to generate hydroxyl radicals from H₂O₂. Industrially, the BOF and EAF routes pour about 1.9 billion tonnes of steel a year, and the rust that eats it back — hydrated Fe(III) oxyhydroxides — is the price of using a metal whose oxidation isn't quite passive enough to protect itself.
Fun Fact
Iron is the endpoint of stellar nucleosynthesis — the heaviest element a star can produce through fusion while still releasing energy. Anything heavier requires the energy of a supernova, which is why iron piles up at the top of the cosmic abundance curve for metals.
Common Uses
- Carbon-steel and stainless-steel production for construction and tooling
- Hemoglobin and cytochrome iron-porphyrin centers in respiration
- Magnetite-based promoted catalyst for the Haber-Bosch process
- Soft-iron cores in transformers and electric motor laminations
- Fenton-reagent (Fe²⁺/H₂O₂) treatment of organic-loaded wastewater