Titanium

Symbol: Ti

Atomic Number: 22

Atomic mass: 47.867 amu (atomic mass units)

Melting Point: 1668 C (1941 K, 3034 F)

Boiling Point: 3287.0 C (3560.15 K, 5948.6 F)

Number of Electrons: 22
Number of Protons: 22

Number of Neutrons: 26

Classification: Transition Metal

Crystal Structure: Hexagonal

Density @293 K: 4.54 grams per cubic centimeter

Color: Silver

Titanium, the ninth most abundant element on earth, was discovered, in 1791 by the English pastor Reverend William Gregor. The Reverend Gregor had an interest in minerals and recognized a new element in the mineral menachanite. L. F. Nilson and O. Pettersson first prepared an impure sample of titanium metal. The pure element was not isolated until 1910 when the American metallurgist Mathew A. Hunter produced titanium metal by heating titanium tetrachloride (TiCl4) with sodium. This was carried out in a steel bomb at temperatures between 700 C (973K, 1292 F) and 800 C (1073K, 1472 F). The element was named by Martin Heinrich Klaproth in 1795 after the Titans who, in Greek mythology, were the sons of the earth goddess.

Titanium comprises 0.57% of the earth's crust. The gemstones star rubies and star sapphires owe their asterism to a small amount of titanium in their crystalline structure. High proportions of titanium oxide were found in some of the moon rocks obtained by the Apollo Lunar landing missions. Light from M-type stars shows intense spectral bands attributed to titanium oxide.

Titanium metal is as strong as steel but 45% lighter. Pure titanium that is free of oxygen is ductile. The metal is extremely resistant to corrosion and cannot be corroded by dilute hydrochloric or sulfuric acids, organic acids or chloride solutions. Titanium can burn in air and is the only element that can burn in a nitrogen atmosphere. The metal is dimorphic with the hexagonal alpha form changing slowly to the cubic beta form at 880 C (1153K, 1616F).

Although titanium has no biological role, it is hypoallergenic (does not provoke an allergic response). As it also resists corrosion by bodily fluids, it is used to make replacement joints and pins to hold together broken bones

Natural titanium is comprised of five stable isotopes. In order of abundance, these isotopes are titanium-48 (73.72%), titanium-46 (8.25%), titanium-47 (7.44%), titanium-49 (5.41%) and titanium-50 (5.18%). There are a number of unstable isotopes of titanium with mass numbers ranging from 38 to 61.

Titanium only became widely available for industrial use after William J. Kroll developed the Kroll process in 1940. Commercial quantities of titanium occur in the minerals rutile, ilmenite and sphene.

In addition to its medical uses, titanium's corrosion resistance makes it useful for ships propellers and rigging. It may also be of use in desalination plants. Titanium and titanium alloys are used in missiles and rockets where a lightweight heat resistant metal is required.

Titanium oxide (TiO2) is used as a pigment in white paint. This is the largest industrial application of titanium. Pure titanium oxide can be used to make artificial gemstones. As paint containing titanium reflects infra red, this type of paint is used on solar observatories.

Another titanium compound, titanium tetrachloride (TiCl4), is used to make smoke screens as it fumes in air. This compound is also used to iridize glass.

Reference Sources:

Los Alamos National Laboratory's Chemistry Division

Jefferson Lab Science Education

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