Titanium is a chemical element or light silvery metal of Group 4 (IVB) in the periodic table with the symbol Ti and atomic number 22. It has a high melting point, good tensile strength, and properties of thermal and electrical conductance. It forms a hexagonal close-packed crystal lattice like most of the other transition metals. It is a very useful metal uses widely in industry. Titanium alloy is mostly used in high-speed aircraft. The valence shell electronic configuration of metal is 3d2 4s2. Therefore, the highest and most stable oxidation number or state of titanium is +4.
Who discovered titanium?
In 1791, the English chemist and mineralogist William Gregor attempted to discover a new metal from titaniferous iron ore, ilmenite (FeTiO3) but actually isolated impure oxide. In 1794, German chemist Martin Heinrich Klaproth also prepared the same oxide from mineral rutile and named the element, titanium comes from Greek latter Titans.
Good qualities, corrosion resistance titanium has valence shell electron configuration [Ar] 3d2 4s2 and common oxidation number +4.
|Properties of titanium|
|Electronic configuration||[Ar] 3d2 4s2|
|Meting point||1668 °C|
|Boiling point||3287 °C|
|Molar heat capacity||25.06 J mol-1 K-1|
|Electronegativity||1.54 (Pauling scale)|
|Ionization energy||1st – 658.8 kJ/mol
2nd – 1309.8 kJ/mol
|Crystal structure||hexagonal close-packed (hcp)|
|Electrical resistivity||420 nΩ⋅m at 20 °C|
Where is titanium found?
Titanium is the ninth most abundant among all elements and second, among the transition metals, constitutes nearly 0.63 percent of the earth’s crust. The combined form of metal is found in most igneous rocks, sand, clay, and soils, in the living organisms (plant and animal), and natural bodies of water. The metal was isolated by metallurgist Berzelius in 1825 and the pure form by M. Hunter in 1910 by reducing titanium chloride (TiCl4) with an airtight steel cylinder.
Ilmenite (FeTiO3) and Rutile (TiO2) are two commercial ores of titanium, principally occur in western Australia, Canada, China, South India, Mozambique, Malaysia, New Zealand, Norway, Sierra Leone, South Africa, and Ukraine.
Natural titanium consists of five stable isotopes like 46Ti (8.0 percent), 47Ti (7.3 percent), 48Ti (73.8 percent), 49Ti (5.5 percent), and 50Ti (5.4 percent).
The preparation of pure titanium very difficult due to its reactivity at high temperatures. The extraction of metal by carbon reduction produces a number of difficulties. It is highly reactive at high temperatures and readily forms carbide, nitride, and oxide by the reaction with carbon, oxygen, and nitrogen respectively. The extraction of the metal was carried out by heating ilmenite or rutile with carbon and chlorine at 900 °C. Titanium tetrachloride (TiCl4), boiling point 137 °C, is separated from FeCl3 by fractional distillation. The TiCl4 is reduced by molten magnesium in an argon atmosphere to produce spongy titanium (TiCl4 + 2Mg → Ti + 2MgCl2).
Magnesium chloride and excess magnesium are removed by washing water and dilute hydrochloric acid. Pure titanium is obtained by heating the metal with iodine in an evacuated glass tube fitted with a tungsten filament at the center of the tube.
Facts about titanium
- Titanium is a high melting, good tensile strength, and corrosion resistance transition metal of Group 4 of the periodic table.
- The metal is unreactive at ordinary temperature but in a finely divided state, it catches fire in the air (pyrophoric).
- On heating, it combines with nonmetals like oxygen, nitrogen, boron, carbon, silicon, and hydrogen.
- The nitride (TiN), carbides (TiC), borides (TiB, TiB2) are very hard, a good conductor of electricity, and chemically very inert compounds.
- The metal decomposes by steam at 100 °C but not attacked by dilute mineral acids like sulfuric acid, hydrochloric acid, or nitric acid at ordinary temperature. It does not attack by hot aqueous alkali but fused alkali attacks it to give titanates.
In learning chemistry, the valence shell electron configuration, 3d2 4s2, therefore the highest and most stable oxidation state of Ti is +4. The compounds of a lower oxidation state (0, II, III) readily oxidized to form Ti(IV). The high ionization energy required to form Ti+4 ion that suggests the chemical compounds of +4 state are formed by covalent bonding.
The most important oxide, titanium oxide (TiO2) has three crystalline solid forms like rutile, anatase, brookite. From which rutile being the most common naturally occurring form uses in chemical industries as a pigment. In all the structures, Ti is coordinated to six oxygen atoms, octahedrally in rutile and destroyed octahedral environment in others. Ti2O3, violet color oxide of Ti(III) has a structural type similar to that of α-Al2O3. TiO may be made by heating TiO2 with metallic titanium from a cubic crystalline structure like sodium chloride but usually non-stoichiometric with one-sixth vacant sites for both ions. It is used as a metallic conductor.
All four halides of titanium (TiF4, TiCl4, TiBr4, and TiI4) are known. TiF4 may be obtained by reacting the metals with fluorine at 200 °C but other tetra-halides may be prepared by heating TiO2 with carbon and halogen. Ti(III) forms all the four halides molecules which are insoluble in water and stable in air. These disproportionate to form Ti(IV) halides.
Organometallic compounds of titanium were developed in 1960 by the discovery of the Ziegler Natta chemical catalyst. A large number of organometallic compounds obtain by chemical bonding like sigma and pi-bond. The most common organotitanium complex is titanocene dichloride [(C5H5)2TiCl2]. Tebbe’s reagent and Petasis reagent are the related compounds of titanocene dichloride.
Uses of Titanium
- Due to high efficiency and low biological toxicity, titanium(IV) complex are the first non-platinum compounds tested for the treatment of cancer in medicine.
- Titanium is an impotent alloying material due to its low density, high tensile strength, and excellent corrosion resistance. The addition of 0.1 percent of titanium to steel increases the mechanical strength and corrosion resistance of alloy. These alloy are used in many chemical and industrial fields like storing alkaline solution, chlorine compounds, moist and other aggressive chemicals, making rails, railway wheels, and excels.
- It alloys with manganese, chromium, iron, molybdenum, aluminum, vanadium and tin have advantages of lightness and good mechanical strength. It is used mainly in aeronautical and missile industries.
- Ferrotitanium is prepared by smelting ilmenite or rutile with iron and coke in an electric furnace, used as a scavenger in the steel industry to remove oxygen and nitrogen from steel.
- In chemistry, titanium oxide (TiO2) is extensively used as white pigment due to its excellent covering power, which is prepared along the same route of metal extraction.