The element titanium is a silver colored metal found in group 4 and period 4 of the periodic table. The atomic number of titanium is 22 and it has an atomic mass of 47.867.
It is the ninth most common element on earth but it is not found as a free metal naturally. Instead, titanium occurs in a number of mineral ores, principally rutile, ilmenite and sphene. It is also present in titanates and iron ores. Naturally occurring titanium has five stable isotopes, with mass numbers ranging from 46 to 50.
By weight, crustal rocks contain 6,600,000 ppb of titanium. The overall abundance in the universe is 3,000 ppb and our sun contains 4,000 ppb of titanium. Some lunar rocks, brought back to earth by the Apollo lunar landing missions, are rich in titanium dioxide. Those brought back by the Apollo 17 mission contained 12.1% titanium; other rocks from previous missions had lower percentages of titanium. Other sources of extraterrestrial titanium include carbonaceous meteorites, which contain about 550,000 ppb by weight. The spectra produced by M-class stars (red stars) have prominent bands equating to the presence of titanium oxide.
The pastor Reverend William Gregor discovered titanium while studying a sample of the mineral menachanite in 1791. He did not name his newly found element and in 1795, Martin Heinrich Klaproth named it after the Titans of Greek mythology. It was not until 1910 that Mathew A. Hunter produced a pure sample of the element. Economic industrial usage of titanium started after William J. Kroll developed the Kroll process in 1940.
A pure sample of titanium, free of any oxygen, is extremely ductile. The metal is as strong as steel but far lighter. In addition to being strong, titanium is corrosion resistant making it useful for the production of marine equipment such as ship’s propellers. As it is physiologically inert (does not react to body fluids or act as an allergen) it is of use in the production of replacement joints and pins used in orthopedic surgery. Other uses for the pure metal include the production of missiles and rockets.
Many white paints contain titanium oxide as a pigment. Another compound of use is titanium tetrachloride, which fumes in air and so is used in the production of smoke screens.
The artificial gemstone, titania is formed from titanium oxide. The natural gemstones star rubies and star sapphires owe their asterism to a small amount of titanium in their crystalline structure.
Pure titanium has a dimorphic crystalline structure at temperatures below 880 C (1153K, 1616F) the hexagonal alpha form exists. When heated above 880 C this slowly changes into the cubic beta form.
Titanium has a unique property. In addition to burning in air, it is the only element that can burn in a nitrogen atmosphere.
Los Alamos National Laboratory’s Chemistry Division
Jefferson Lab Science Education