22 Ti 47.867

Titanium

Transition metal Titanium solid

[Ar] 3d² 4s² · 2 · 8 · 10 · 2

← Sc Scandium V Vanadium →

The structural metal with industry's best strength-to-weight ratio and complete immunity to seawater. Titanium is as strong as steel at nearly half the mass, and the body accepts it as its own.

3D model

Bohr model: nucleus and electron shells from the real configuration. Valence electrons are highlighted.

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Atomic properties

Atomic number: 22
Atomic mass: 47.867 а.е.м.
Electron configuration: [Ar] 3d² 4s²
Electrons per shell: 2 · 8 · 10 · 2
Block: d-block
Group: Titanium group
Period: 4
Electronegativity (Pauling): 1.54
Electronegativity (Allen): 1.38
Atomic radius: 176 pm
Covalent radius: 160 pm
Van der Waals radius: 187 pm
Ionisation energy 1: 658.8 kJ/mol
Ionisation energy 2: 1 309.8 kJ/mol
Ionisation energy 3: 2 652.5 kJ/mol
Ionisation energy 4: 4 174.6 kJ/mol
Ionisation energy 5: 9 581 kJ/mol
Electron affinity: 7.6 kJ/mol
Common oxidation states: +4
Oxidation states: -2, -1, +1, +2, +3, +4

Physical properties

State at 25 °C: solid
Density: 4.506 g/cm³
Melting point: 1 941 K · 1 667.9 °C
Boiling point: 3 560 K · 3 286.9 °C
Speed of sound: 4 140 m/s

Thermal properties

Heat of fusion: 14.15 kJ/mol
Heat of vaporisation: 425 kJ/mol
Specific heat capacity: 0.523 J/(g·K)
Thermal conductivity: 21.9 W/(m·K)

Mechanical properties

Young's modulus: 116 GPa
Shear modulus: 44 GPa
Bulk modulus: 110 GPa
Poisson ratio: 0.32
Mohs hardness: 6
Brinell hardness: 716 MPa

Electrical and magnetic properties

Electrical resistivity: 420 nΩ·m
Magnetic ordering: paramagnetic
Curie point: no data
Néel point: no data
Superconducting point: 0.4 K

Crystal structure

Crystal structure: hexagonal close-packed (hcp)
Lattice constants: a = 295.08 pm · c = 468.55 pm

Abundance

In the crust: 5 650 mg/kg
In the ocean: 0.001 mg/L
In the universe: 3 000 mg/kg
In the human body: no data

Isotopes

Isotope	Abundance	Half-life	Decay mode
⁴⁶Ti	8.25 %	stable	—
⁴⁷Ti	7.44 %	stable	—
⁴⁸Ti	73.72 %	stable	—
⁴⁹Ti	5.41 %	stable	—
⁵⁰Ti	5.18 %	stable	—

Five stable isotopes; titanium-44, half-life 60 years, is observed in supernova remnants as direct evidence of recent nucleosynthesis.

Discovery

Year of discovery: 1791
Discovered by: William Gregor
Where: England
Origin of the name: named after the Titans, children of Gaia in Greek myth

History

William Gregor found a new oxide in Cornish black sand in 1791. Klaproth rediscovered it and named it after the Titans. Pure ductile metal was not made until 1910, and the industrial Kroll process arrived in 1940.

Where it occurs

The ninth most abundant element in the crust at 5650 mg/kg. The main minerals are ilmenite and rutile, mined from coastal sands in Australia, South Africa and China.

How it is produced

The Kroll process: chlorinate the ore to TiCl₄ and reduce it with magnesium under argon. It is expensive and batch-wise, which is exactly why titanium costs so much more than steel.

Role in living things

No biological role, but exceptionally biocompatible: the body does not read it as foreign and does not reject it.

Safety

The metal is safe. The carcinogenicity of inhaled titanium dioxide nanoparticles is debated, and the EU banned it as the food additive E171 in 2022.

Uses

Aerospace: up to a third of a modern airframe's mass
Medical implants from dental posts to joint replacements — titanium fuses with bone
Chemical plant and desalination gear that must survive chlorides
Titanium dioxide as a white pigment — the element's largest use by tonnage
Hulls and fittings for marine equipment

Curiosities

95 % of titanium mined becomes white pigment for paint, paper and toothpaste, not metal.
Titanium does not corrode in seawater: parts recovered after decades look new.
The SR-71 was 85 % titanium, bought through front companies from the USSR.
Heated in air, titanium grows an oxide film that produces iridescent colour with no dye at all.