Iron Properties of a Transition Metal
Introduction
Iron (Fe), atomic number 26, is the most abundant transition metal in Earth’s crust and a cornerstone of metallurgy and biochemistry. Its versatile oxidation states and magnetic properties make it critical in industry, materials, and life processes.
Occurrence & Extraction
Iron is primarily found as hematite (Fe₂O₃) and magnetite (Fe₃O₄). Extraction involves reduction of these ores in a blast furnace using coke and limestone:
Fe₂O₃ + 3 CO → 2 Fe + 3 CO₂ Fe₃O₄ + 4 CO → 3 Fe + 4 CO₂
Physical Properties
- Silvery-gray metal with a slight reddish tinge
- Melting point: 1538 °C; boiling point: 2862 °C
- Density: 7.87 g cm⁻³
- Ferromagnetic below Curie point (770 °C)
- Malleable, ductile, and good conductor of heat and electricity
Chemical Properties
- Reactivity with oxygen: Forms rust (hydrated Fe₂O₃) in moist air; protective oxide layer forms at high temperatures.
- Reaction with acids:
Fe + 2 HCl → FeCl₂ + H₂↑
- Reaction with bases: Amphoteric behavior:
Fe + 2 NaOH + 2 H₂O → Na₂[Fe(OH)₄]
- Complex formation: Forms numerous coordination compounds (e.g., hexaquoiron(II), hexaquoiron(III)).
Oxidation States
Common oxidation states of iron are +2 and +3:
| Oxidation State | Species | Color |
|---|---|---|
| +2 | Fe²⁺ | Pale green |
| +3 | Fe³⁺ | Yellow/brown |
Important Reactions
Formation of Rust
4 Fe + 3 O₂ + x H₂O → 2 Fe₂O₃·xH₂O
Redox Between Fe²⁺ and Fe³⁺
Fe³⁺ + e⁻ → Fe²⁺ Fe²⁺ – e⁻ → Fe³⁺
Applications
- Steel production (alloys of Fe and C)—foundation of construction and machinery
- Cast iron and wrought iron for tools, pipes, and engines
- Hemoglobin contains Fe²⁺ for oxygen transport in blood
- Catalysts in Haber process (Fe) and Fischer–Tropsch synthesis
- Magnetic materials and data storage
Conclusion
Iron’s abundance, multiple oxidation states, and magnetic and mechanical properties make it indispensable in technology, construction, and biology. Mastering its chemistry is vital for understanding industrial processes and life’s molecular machinery.
