Titanium

Titanium,  ₂₂Ti

Titanium shavings.
General properties
Name, symbol	Titanium, Ti
Pronunciation	/tɪˈteɪniəm/
Appearance	Silvery white
Titanium in the periodic table
- ↑ Ti ↓ Zr Scandium ← Titanium → Vanadium
Atomic number	22
Standard atomic weight (Ar)	47.87
Group, block	4; d-block
Period	period 4
Electron configuration	[Ar] 3d2 4s2
per shell	2, 8, 10, 2
Physical properties
silvery,metalic
Phase	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	4.11 g/cm3
Heat of fusion	14.15 kJ/mol
Heat of	425 kJ/mol
Molar heat capacity	25.060 J/(mol·K)
pressure
Atomic properties
Oxidation states	4, 3, 2, 1, −1, −2 ​(an amphoteric oxide)
Electronegativity	Pauling scale: 1.54
energies	1st: 658.8 kJ/mol 2nd: 1309.8 kJ/mol 3rd: 2652.5 kJ/mol
Atomic radius	empirical: 147 pm
Covalent radius	160±8 pm
Miscellanea
Crystal structure	​ hexagonal close-packed (hcp)
Speed of sound thin rod	5090 m/s (at )
Thermal expansion	8.6 µm/(m·K) (at 25 °C)
Thermal conductivity	21.9 W/(m·K)
Electrical resistivity	420 Ω·m (at 20 °C)
Magnetic ordering	Paramagnetic
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 Registry Number	7440-32-6
History
Discovery	William Gregor (1791)
First isolation	Jöns Jakob Berzelius (1825)
Named by	Martin Heinrich Klaproth (1795)

Titanium is a transition metal with the symbol Ti and the atomic number 22. It is a grayish, light metal that has high corrosion resistance, but can be converted to multiple oxidation states, most commonly +4 and +3.

Properties

Physical properties

Titanium is a gray metal of low density, only 60% more than that of aluminium, but is twice as strong. It is a common refractory material, and prized for its mechanical properties. It is slightly paramagnetic and exists in three allotropes. Its electrical conductivity is relatively poor for a metal.

Chemical properties

Although titanium does not appear to be reactive, as it does not corrode and generally resists attack by concentrated acids or bases, it has a very strong affinity to oxygen. Its reactivity is masked by the formation of a passivating oxide layer of titanium dioxide on the surface. Titanium will ignite at temperatures exceeding 1,200 °C to form the oxide and nitride in air. Therefore, melting titanium must be done in an inert atmosphere. The flame is white, but slightly yellowish compared to a magnesium flame.

Titanium(IV) is the most common oxidation state of the element. Compounds of titanium(IV) are extremely difficult to dissolve in aqueous solution as the TiO²⁺ (titanyl) ion only exists in highly acidic conditions. However, it can be produced very easily. The most common titanium(IV) compound is the oxide. Titanium(IV) chloride is a powerful Lewis acid that hydrolyzes to hydrogen chloride and titanium dioxide in the presence of water. Titanium(IV) also forms stable peroxo complexes, which are quite colorful.

Titanium(III) compounds are also accessible to the amateur. When added to hot concentrated hydrochloric acid, titanium dissolves to form titanium(III) chloride, which exists as a purple solution. Most titanium(III) compounds are bluish-purple due to the lone d electron, however, this purple color is not very strong due to the low probability of the transition. This is a good starting point for the production of many titanium compounds, such as titanium(III) oxide. Mixed titanium(III,IV) fluoro complexes can be produced, though they have not been studied well.

The metal also dissolves quite easily in hot, 50 w% sulphuric acid, forming purple Ti(III) sulphate. Stable solutions up to about 30 w% of Ti₂(SO₄)₃ can be obtained this way. When CsCl solution is added to these solutions CsTi(III) alum precipitates.

Titanium(II) compounds also exist, but these are very difficult to produce, as they reduce many materials, including water.

Isolation

Titanium can be prepared by reducing titanium tetrachloride with magnesium, though this reaction is difficult for the amateur chemist as both titanium and its chloride are sensitive to water and air. Industrially, this reaction is performed in vacuum (Kroll process).

An easier route to preparing titanium metal is through a thermite reaction between titanium dioxide and aluminium. The reaction doesn't proceed smoothly on its own, however, and instead must be boosted with a side reaction between aluminium and calcium sulfate, or some other booster. If large nodules of the metal are desired, about one part calcium fluoride per every two parts titanium dioxide can be used to help the mixture melt together. The resulting titanium contains about 10 % of Al, some as alloyed metal, some as alumina slag inclusions. The obtained Ti is also non-ductile, as ductile Ti can only be obtained by the anaerobic Kroll process.

Availability

Anodized titanium earrings

Titanium is available in over 50 grades. Grades 1 through 4 are pure titanium, with the largest impurity being oxygen atom replacements in the crystal lattice. The other grades are titanium alloys.

Projects

• Titanium salutes, sparklers, and other pyrotechnics
• Thermite boosed with calcium sulfate
• Titanium tetrachloride synthesis
• Titanium electrodes
• Titanium halogen salts
• Anodizing titanium metal produces a wide range of colors:

Handling

Safety

Titanium powder and turnings can be flammable. Finely dispersed titanium dust can ignite spontaneously with electrical sparks or open flames, causing a flashover. Bulk titanium, however, is extremely difficult to ignite.

Storage

No special storage is required for titanium. Powdered titanium however should be stored in a low oxygen container.

Disposal

Titanium and titanium compounds are non-toxic and do not require special disposal.

References

Relevant Sciencemadness threads

• titanium chemistry