Iron

Iron (symbol Fe, atomic number 26) is a metal in Group 8 and part of the first transition series in the periodic table. It is a lustrous, ductile, and malleable metal with a silver-grey colour. Iron ranks as the tenth most abundant element in the universe, and it exists in significant quantities in the Earth's core, where it remains molten due to extreme heat and pressure.

1.0Introduction   

In the universe, iron ranks as the tenth most abundant element, and it exists in significant quantities in the Earth's core, where it remains in a molten state due to the extreme heat and pressure. Iron is crucial in forming much of the Earth's inner and outer core and ranks as the fourth most common element in the Earth's crust.

In its pure form, iron is a silvery-white metal known for its ability to retain a magnetic field and dissolve small amounts of carbon when molten, producing steel. Commercial refining of iron involves heating iron oxides like Fe₂O₃ or Fe₃O₄ (magnetite) with other substances in a high-temperature blast furnace, where the oxides are reduced to pure iron. Small amounts of carbon and other metals are added to molten iron to harden it, and iron castings or forgings can be heat-treated to optimise various physical properties depending on the solid phases of iron.

On the other hand, pure iron easily combines with moisture and oxygen to cause harmful corrosion. Steel and other iron alloys need to be protected from structural degradation with coatings or paints.

2.0Physical Properties of Iron

Iron is a silvery-white or grey metal that is both malleable, meaning it can be drawn into thin wires, and malleable, meaning it can be hammered into thin sheets.

3.0Chemical Properties of Iron

1. Oxidation States:

• Iron commonly exhibits +2 (ferrous) and +3 (ferric) oxidation states. Iron(II) compounds are pale green, while iron(III) compounds are orange/brown.
• Iron can also exist in higher oxidation states, such as +6 in potassium ferrate (K₂FeO₄).

2. Reaction with Oxygen: Iron reacts with oxygen and moisture in the air to form rust (Fe₂O₃): 4Fe(s)+3O₂(g)→2Fe₂O₃(s)
3. Reaction with Water: Iron doesn’t react with cold or hot water but reacts with steam to form iron oxide and hydrogen: 3Fe(s)+4H₂O(g)→Fe₃O₄(s)+4H₂(g)
4. Reaction with Halogens: Iron reacts with halogens to form iron halides:

• With chlorine: 3C_l2(g)+2Fe(s)→2FeCl₃(s) (dark brown)
• With bromine: 3Br₂(l)+2Fe(s)→2FeBr₃(s) (reddish brown)

5. Reaction with Acids: Iron reacts with acids, displacing hydrogen to form salts: Fe(s)+H₂SO₄(aq)→FeSO₄(aq)+H₂(g)
6. Reaction with Hydroxide Ions: Iron(II) ions form a white precipitate with hydroxide ions: Fe²⁺(aq)+2OH⁻(aq)→Fe(OH)₂(s)
7. Reaction with Phosphate Ions: Phosphate ions do not precipitate Fe(II) but precipitate Fe(III) in acetic acid: Fe³⁺(aq)+H₂PO₄⁻ → FePO₄(s) + 2H⁺(aq)
8. Iron as a Catalyst: Iron catalyzes critical chemical reactions because of its ability to alternate between oxidation states.

• The Haber Process: Iron speeds up the industrial synthesis of ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂), facilitating the breaking of nitrogen’s strong triple bond: 

    N₂(g)+3H₂(g)⇌2NH₃(g)

• Persulfate-Iodide Reaction: Iron(II) or iron(III) ions catalyse the reaction between persulfate (S₂O₈²⁻) and iodide (I⁻), alternating between oxidation states. Iron is a silvery-white or grey metal that is malleable, meaning it can be drawn into thin wires and hammered into thin sheets.

S₂O₈²⁻+2I⁻→2SO₄²⁻+I₂

4.0Corrosion of Iron

Rusting is a process that causes iron things to degrade over time and sustain major damage. Since iron is frequently used to build automobiles, trucks, ships, bridges, and other structures, rusting results in significant financial losses. Rust production is accelerated in the presence of high air moisture content. The following equation can be used to illustrate the rusting process: 

                4Fe + 3O₂​ + xH₂​O → 2Fe₂​O_3​⋅xH_2​O

Prevention of  Rusting

Iron should not be exposed to water, air, or both in order to prevent rust. These are a few ways to keep iron from rusting. These techniques extend the preservation times of iron items.

Painting or Greasing:

• Putting on a coating of paint or grease creates a barrier between the surroundings and the iron.
• Constant protection from these coatings requires routine maintenance.

Galvanization:

• To do this, apply a layer of zinc on the iron, providing a shield that stops rust.
• Galvanised iron pipes, frequently used in homes to transmit water, feature effective corrosion resistance.
• This technique gives iron objects a thin layer of metal, improving their look and preventing corrosion.

Chromium Coating:

• Chromium coating is another way to prevent corrosion and give iron a glossy appearance.

Electroplating:

• This process applies a thin metal coating on iron objects, enhancing their appearance and shielding them from corrosion.

5.0Uses of Iron

1. Construction: Because of their strength and accessibility, iron rods are used in the construction of infrastructure and structures worldwide.
2. Home Appliances: Due to its durability and accessibility, iron is used in the construction of numerous household appliances, including cooking stoves, dishwashers, pans, plates, and cutlery.
3. Function in Biology: Iron is an essential part of hemoglobin, which helps oxygen get throughout the body.
4. Magnets: Iron is a component of many magnets, including magnetite, a naturally occurring permanent magnet.
5. Tools & Equipment: Hammers, knives, and swords were among the earliest tools made of iron in the past. These days, it's used to make powerful cutting tools and other machinery.
6. Iron Compounds: 

• Iron(III) Oxide (Fe₂O₃): Also known as ferric oxide or hematite, this is used to produce iron in blast furnaces.
• Iron(III) Oxide-Hydroxide (FeO(OH)): This material, which ranges in colour from yellow to black, binds phosphates in aquarium water treatment.
• Iron(II) Sulfate (FeSO₄): Commonly used to treat iron-deficiency anaemia and as an additive in various foods.

7. Steel Manufacturing: Iron is primarily used in steel production and has a wide range of applications due to its strength and versatility.
8. Cast Iron: Cast iron, which contains 3-5% carbon, manufactures items like pumps, pipes, and valves.
9. Civil Engineering and Construction: Iron and steel are essential in civil engineering, particularly construction and infrastructure projects.