Titanium (Ti)

Introduction: Why Titanium Matters

Titanium (Ti) is a chemical element renowned for its exceptional strength-to-weight ratio and remarkable corrosion resistance. These properties make it indispensable in demanding applications where both lightness and durability are crucial. Its real-life significance spans from advanced aerospace components and high-performance sports equipment to biocompatible medical implants and durable industrial applications.

CBSE/JEE Quick Revision Notes

Symbol: Ti
Atomic Number (Z): 22
Atomic Mass: 47.867 u (or approximately 48 g/mol)
Group: 4
Period: 4
Block: d-block (Transition Metal)
Nature: Lustrous, silvery-white metal.
Density: Relatively low (4.506 g/cm³ at 25 °C), making it light for its strength.
Melting Point: 1668 °C (high)
Boiling Point: 3287 °C (very high)
Common Oxidation States: +2, +3, +4 (Most stable and common is +4).
Physical State at STP: Solid.
Key Property: Excellent corrosion resistance due to the formation of a stable, adherent, and protective oxide layer on its surface (passivation).

Electron Configuration & Bonding Behavior

Ground State Electron Configuration: [Ar] 3d² 4s²
Valency and Oxidation States:
- Titanium exhibits variable oxidation states characteristic of transition metals.
- The 4s electrons are lost first, followed by 3d electrons.
- +4 Oxidation State: Most stable and prevalent. Formed by the loss of both 4s electrons and both 3d electrons. Compounds like TiO₂ and TiCl₄ are common and stable in this state.
- +3 Oxidation State: Less stable than +4. Ti³⁺ compounds (e.g., TiCl₃) are often colored and paramagnetic (due to one unpaired 3d electron).
- +2 Oxidation State: Least stable of the common states. Ti²⁺ compounds (e.g., TiO, TiCl₂) are strong reducing agents.
Bonding: Forms primarily ionic compounds in its higher oxidation states (e.g., TiO₂). However, some compounds, especially TiCl₄, exhibit significant covalent character due to the high charge density of the Ti⁴⁺ ion and polarizing power.

Crucial Chemical Reactions

1. Reaction with Oxygen

Titanium reacts with oxygen to form a very stable titanium dioxide layer, which provides corrosion resistance. Ti(s) + O₂(g) → TiO₂(s) (at high temperatures, or slowly at room temperature forming a protective layer)

2. Reaction with Halogens

Titanium reacts vigorously with halogens, particularly chlorine, to form titanium tetrahalides. This reaction is crucial in the industrial extraction process (Kroll process). Ti(s) + 2Cl₂(g) → TiCl₄(l) (Titanium tetrachloride, a volatile liquid)

3. Reaction with Acids

Titanium is generally resistant to dilute mineral acids (like dilute HCl, H₂SO₄) at room temperature due to its passivating oxide layer.

With Hydrofluoric Acid (HF): It reacts readily due to the formation of stable fluoro-complexes. 2Ti(s) + 6HF(aq) → 2TiF₃(aq) + 3H₂(g) (or more complex reactions forming [TiF₆]³⁻)
With Hot Concentrated Sulfuric Acid: 2Ti(s) + 6H₂SO₄(conc, hot) → Ti₂(SO₄)₃(aq) + 3SO₂(g) + 6H₂O(l)

4. Kroll Process (Industrial Extraction of Titanium)

This is the primary method for producing titanium metal. Step 1: Chlorination of Titanium Dioxide (Rutile ore) TiO₂(s) + 2Cl₂(g) + 2C(s) → TiCl₄(g) + 2CO(g) (at ~900 °C) Step 2: Reduction of Titanium Tetrachloride TiCl₄(g) + 2Mg(l) → Ti(s) + 2MgCl₂(l) (at ~800-850 °C, using molten magnesium)

Industrial and Biological Importance

Industrial Importance

Titanium Dioxide (TiO₂):
- Pigment: The most significant use. TiO₂ is an exceptionally white, opaque, and non-toxic pigment used extensively in paints, coatings, plastics, paper, and textiles.
- UV Absorber: Used in sunscreens and cosmetics to block harmful UV radiation.
- Photocatalyst: Used in self-cleaning surfaces and air/water purification due to its photocatalytic properties.
Titanium Metal and Alloys:
- Aerospace Industry: High strength-to-weight ratio and corrosion resistance make it ideal for aircraft frames, jet engine components, and spacecraft.
- Biomedical Implants: Biocompatibility and inertness lead to widespread use in surgical implants (e.g., hip and knee replacements, dental implants, bone plates). It is not rejected by the human body.
- Marine Applications: Excellent corrosion resistance to seawater makes it suitable for marine equipment, submarine components, and offshore oil rigs.
- Chemical Processing: Used in chemical plants for tanks, heat exchangers, and pipes where highly corrosive chemicals are handled.
- Sports Equipment: Used in high-performance items like golf clubs, bicycle frames, and tennis rackets.

Biological Importance

Biocompatibility: Titanium is highly biocompatible, meaning it is non-toxic and not harmful to living tissues. This property is crucial for its extensive use in medical and dental implants.
No Essential Biological Role: Unlike some other trace elements, titanium is not known to be an essential element for human or animal nutrition or metabolism. Its presence in biological systems is generally incidental, though it is considered inert.

Titanium (Ti) - Comprehensive Study Guide