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CHEMICAL-PHYSICAL PROPERTIES
- Atomic number: 22
- Atomic weight: 47.90
- Electronic configuration: [Ar] 3d2 4s2
- Density (g/cc): 4.506
- Melting point (C): 1677
- Boiling point (C): 3277
- Presence in the lithosphere: 0.4%
- Electrode standard potential (V): -1.63 (Ti++/Ti)

PRESENCE IN NATURE AND PRODUCTION
This is thr 9th element for its abundance in the Earth crust, but often too dispersed to be extracted.

As pure metal, it's present in the meteorites, for the rest exist only combined, mainly as TiO2 (titanium dioxide, or RUTILE), but also as ILMENITE (FeTiO3), or TITANITE (CaTiO3).

Its extraction is rather complex because, at high temperature, it reacts with the normal reducing reagents used in metallurgy (C, Al) and also, with N2 of the air.
One of the main processes is the KROLL process; reduction with metallic Na, Mg or H2 of the chloride, TiCl4, obtained from TiO2 or FeTiO3.
To get a high purity, the Van Arkel and De Boer is the best; the impure Ti reacts with I2 to obtain TiI4, whose vapour is decomposed on a hot tungsten wire releasing pure Ti.

CHEMICAL PROPERTIES
As we can see from its properties, it's a very light metal, less than iron and steel. Then, it's harder than aluminium, with a resistance to corrosion nearly equal to that of Platinum, one of the most noble metals. Its appearance is silver-like and it's easy to be worked.

When in thin powder, it burns with the O2 of the air and, at higher temperature, it's the only element burning with N2.

Given its highly negative electrode potential, it can't be reduced by electrolysis in water solution

Its more stable oxidation number is +4, but there're also compounds with +3 and +2.
In aqueous solution Ti++++ doesn't exist, because of its excessive electric field, but only in the TiO++ (Titanyl ion) form, formed immediately by the hydrolysis of its salts:
Ti(SO4)2 + 3 H2O <===> TiO++ SO4- + 2H2O + SO4-
TiO++ + 3H2O -> TiO2 + 2 H2O

Metallic Ti absorbes H2 forming HYDRIDES (TiH, TiH2, maybe TiH4) that, about 1000 C, decompose releasing the metal.

TiO2 is white, highly inert, and only with H2SO4 it gives Ti(SO4)2

The salts of Ti IV, like TiCl4, are among the strongest Lewis acids known and it's liquid and colourless.

Its salts with oxidation number III, like TiCl3, are intensely coloured, less stable and strongly reducing.

USES
- Ti: the favorable properties mentioned above make the use of Ti and its alloys very frequent for engines, airplanes and ships production, for pipelines, valves, tools and electrodes to be used in extreme conditions.
Another recent use is that of the prosthesis for surgery, given its biological inertness.

- TiO2: it's very used as refractory and is chemically very inert.
One of its main uses is as a white pigment in food and pharmaceutical industry, just for its inertness.

- TiCl4: this compound is used as catalyst in polymerization reactions to produce polyethylene and polypropylene, toghether with aluminium-organic compounds.

- TiC (titanium carbide): (melting point = 3160C) very used in tools for the fast cut of metals.

Learn more about this author, Aldo Bonincontro.
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