Periodic Table
26
Fe
55.845
Iron
Transition MetalMost used metal; Fe²⁺ green, Fe³⁺ yellow/brown; haemoglobin core.
Electronic Configuration
[Ar] 3d⁶ 4s²or1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²
Electron shells
2e⁻n=1
8e⁻n=2
14e⁻n=3
2e⁻n=4
Properties
Atomic number
26
Atomic mass
55.845 u
Category
Transition Metal
Block / Group / Period
d · 8 · 4
Valence electrons
2
Oxidation states
+2, +3
Electronegativity
1.83
Atomic radius
156 pm
Ionization energy
762 kJ/mol
Electron affinity
15 kJ/mol
Melting point
1811 K / 1538 °C
Boiling point
3134 K / 2861 °C
Density
7.874 g/cm³
State at 25 °C
solid
JEE / NEET notes
- Fe²⁺ (3d⁶) pale green; Fe³⁺ (3d⁵, half-filled) yellow/brown — more stable.
- Brown ring test for nitrate: [Fe(H₂O)₅NO]²⁺.
- Rusting = hydrated Fe₂O₃; electrochemical process.
- Fe³⁺ + SCN⁻ → blood-red [Fe(SCN)]²⁺.
Flame test
Gold/orange sparks
Ores & extraction
Ores: Haematite (Fe₂O₃), Magnetite (Fe₃O₄), Iron pyrites (FeS₂), Siderite
Extraction: Blast furnace — reduction of Fe₂O₃ by CO.
Uses
Steel (construction) · Catalyst (Haber) · Magnets
Important compounds
Fe₂O₃FeSO₄·7H₂O (green vitriol)FeCl₃K₄[Fe(CN)₆]
Personal Notes
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