Titanium

Titanium, ₂₂Ti
General properties
Pronunciation	/tɪˈteɪniəm, taɪ-/(tih-TAY-nee-əm, ty-)
Appearance	silvery grey-white metallic
Standard atomic weight (Ar, standard)	47.867(1)
Titanium in the periodic table
	scandium ← titanium → vanadium
Atomic number (Z)	22
Group	group 4
Period	period 4
Element category	transition metal
Block	d-block
Electron configuration	[Ar] 3d2 4s2
Electrons per shell	2, 8, 10, 2
Physical properties
Phase at STP	solid
Melting point	1941 K (1668 °C, 3034 °F)
Boiling point	3560 K (3287 °C, 5949 °F)
Density (near r.t.)	4.506 g/cm3
when liquid (at m.p.)	4.11 g/cm3
Heat of fusion	14.15 kJ/mol
Heat of vaporization	425 kJ/mol
Molar heat capacity	25.060 J/(mol·K)
Atomic properties
Oxidation states	4, 3, 2, 1, −1, −2(an amphoteric oxide)
Electronegativity	Pauling scale: 1.54
Ionization energies	1st: 658.8 kJ/mol; 2nd: 1309.8 kJ/mol; 3rd: 2652.5 kJ/mol; (more);
Atomic radius	empirical: 147 pm
Covalent radius	160±8 pm
	Spectral lines
	Spectral lines
Miscellanea
Crystal structure	hexagonal close-packed (hcp)
Speed of sound thin rod	5090 m/s (at r.t.)
Thermal expansion	8.6 µm/(m·K) (at 25 °C)
Thermal conductivity	21.9 W/(m·K)
Electrical resistivity	420 nΩ·m (at 20 °C)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+153.0·10−6 cm3/mol (293 K)
Young's modulus	116 GPa
Shear modulus	44 GPa
Bulk modulus	110 GPa
Poisson ratio	0.32
Mohs hardness	6.0
Vickers hardness	830–3420 MPa
Brinell hardness	716–2770 MPa
CAS Number	7440-32-6
History
Discovery	William Gregor (1791)
First isolation	Jöns Jakob Berzelius (1825)
Named by	Martin Heinrich Klaproth (1795)
Main isotopes of titanium
γ	–
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Titanium is a chemical element with symbol Ti and atomic number 22. It is a lustrous transition metal with a silver color, low density, and high strength. Titanium is resistant to corrosion in sea water, aqua regia, and chlorine.

Titanium was discovered in Cornwall, Great Britain, by William Gregor in 1791, and was named by Martin Heinrich Klaproth after the Titans of Greek mythology. The element occurs within a number of mineral deposits, principally rutile and ilmenite, which are widely distributed in the Earth's crust and lithosphere, and it is found in almost all living things, water bodies, rocks, and soils. The metal is extracted from its principal mineral ores by the Kroll and Hunter processes. The most common compound, titanium dioxide, is a popular photocatalyst and is used in the manufacture of white pigments. Other compounds include titanium tetrachloride (TiCl₄), a component of smoke screens and catalysts; and titanium trichloride (TiCl₃), which is used as a catalyst in the production of polypropylene.

Titanium can be alloyed with iron, aluminium, vanadium, and molybdenum, among other elements, to produce strong, lightweight alloys for aerospace (jet engines, missiles, and spacecraft), military, industrial processes (chemicals and petrochemicals, desalination plants, pulp, and paper), automotive, agri-food, medical prostheses, orthopedic implants, dental and endodontic instruments and files, dental implants, sporting goods, jewelry, mobile phones, and other applications.

The two most useful properties of the metal are corrosion resistance and strength-to-density ratio, the highest of any metallic element. In its unalloyed condition, titanium is as strong as some steels, but less dense. There are two allotropic forms and five naturally occurring isotopes of this element, ⁴⁶Ti through ⁵⁰Ti, with ⁴⁸Ti being the most abundant (73.8%). Although they have the same number of valence electrons and are in the same group in the periodic table, titanium and zirconium differ in many chemical and physical properties.