- For the software development tool targeting the Symbian OS, see Carbide.c++. A programming tool or software development tool is a program or application that Software developers use to create debug maintain or otherwise Symbian OS is an open Operating system, designed for Mobile devices with associated libraries, User interface frameworks and Carbidec++ is a software development tool for C++ development on Symbian OS.
In chemistry, a carbide is a compound of carbon with a less electronegative element. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 " Electronegativity " is the opposite of " Electropositivity," which describes an element's ability to donate electrons Carbides are important industrially: for example, calcium carbide is a feedstock for the chemical industry and iron carbide, Fe3C (cementite), is formed in steels to improve their properties. Calcium carbide is a Chemical compound with the Chemical formula of Ca[[Carbide C2]] Cementite or iron carbide is a Chemical compound with the formula Fe3C (or Fe2CFe and an Orthorhombic crystal structure
Many carbides can be generally classified by chemical bonding type as follows[1]:
- salt-like ionic compounds
- covalent compounds
- interstitial compounds
- "intermediate" transition metal carbides (a group of carbides that in bonding terms sit between the salt-like and interstitial carbides).
In addition to the carbides there are other groups of binary carbon compounds, i. e. [1]
- graphite intercalation compounds
- alkali metal fullerides
- endohedral fullerenes, where the metal atom is encapsulated inside a fullerene molecule
- metallacarbohedrenes(met-cars) which are cluster compounds containing C2 units. Potassium-graphite-xtal-3D-SF-Bpng|thumb|Space-filling model of potassium graphite (top view]] Graphite intercalation compounds are intercalation compounds with a Graphite
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Examples
Some examples are[1]:-
- Calcium carbide (CaC2) important industrially and an ionic salt
- Silicon carbide (SiC), carborundum, a covalent compound
- Tungsten carbide (often called simply carbide) widely used for cutting tools and an interstitial compound
- Cementite (iron carbide; Fe3C) an important constituent of steel
- Boron carbide
- Tantalum carbide
- Titanium carbide
See Category:Carbides for a bigger list. Calcium carbide is a Chemical compound with the Chemical formula of Ca[[Carbide C2]] Silicon carbide ( is a compound of Silicon and Carbon bonded together to form Ceramics but it also occurs in nature as the extremely rare mineral Tungsten carbide, WC, or tungsten semicarbide, W2C, is a chemical compound containing Tungsten and Carbon, similar Cementite or iron carbide is a Chemical compound with the formula Fe3C (or Fe2CFe and an Orthorhombic crystal structure Boron carbide (chemical formula B4C is an extremely hard Ceramic material used in Tank Armor, Bulletproof vests and numerous Tantalum carbide ( Ta[[Carbon C]] is an extremely hard ( Mohs hardess 9-10 refractory Ceramic material commercially used in Titanium carbide, Ti[[Carbon C]] is an extremely hard ( Mohs 9-9
Types of carbides
Ionic salts
Salt like carbides are formed by the metals of[1]
- group 1 (the alkali metals )
- group 2 (the alkaline earths )
- group 3 (scandium, yttrium and lanthanum)
- group 11(copper, silver and gold)
- group 12 (zinc ,cadmium and mercury)
- only aluminium from group 13, (gallium, indium and thallium do not appear to form carbides). Trends The alkali metals show a number of trends when moving down the group - for instance decreasing electronegativity increasing reactivity and decreasing melting and boiling Biological occurrences Beryllium's low aqueous solubility means it is rarely available to biological systems it has no known role in living organisms and when encountered Scandium (ˈskændiəm is a Chemical element that has the symbol Sc and Atomic number 21 Yttrium (ˈɪtriəm is a Chemical element with symbol Y and Atomic number 39 Lanthanum (ˈlænθənəm is a Chemical element with the symbol La and Atomic number 57 Copper(I acetylide, or cuprous acetylide, is an inorganic chemical compound with the formula Cu 2 C 2 Silver acetylide is an inorganic chemical compound with the formula Ag2C2 a Metal acetylide. Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 Cadmium (ˈkædmiəm is a Chemical element with the symbol Cd and Atomic number 48 Mercury (ˈmɜrkjʊri also called quicksilver or hydrargyrum, is a Chemical element with the symbol Hg ( Latinized hydrargyrum Aluminium carbide, chemical formula Al 4 C 3 is a Carbide of Aluminium. Gallium (ˈgæliəm is a Chemical element that has the symbol Ga and Atomic number 31 Indium (ˈɪndiəm is a Chemical element with chemical symbol In and Atomic number 49 Thallium (ˈθæliəm is a Chemical element with the symbol Tl and Atomic number 81
- lanthanides when forming MC2 and M2C3 carbides
- actinides when forming MC2 and M2C3 carbides
Most commonly they are salts of C22− and are called acetylides, ethynides, acetylenediides or very rarely, percarbides. Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally
Some compounds contain other anionic species:[1]
- C4−, sometimes called methanides (or methides) because they hydrolyse to give methane gas. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas.
- C34− ion, sometimes called sesquicarbides, they hydrolyse to give methylacetylene. Methylacetylene ( propyne) is an Alkyne with the Chemical formula H 3C≡CH
The naming of ionic carbides is not consistent and can be quite confusing.
Acetylides
The polyatomic ion C22− contains a triple bond between the two carbon atoms. A polyatomic ion is a charged species ( Ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered as acting Examples are the carbides of the alkali metals e. g. Na2C2, some alkaline earths, e. g. CaC2 and lanthanoids e. Calcium carbide is a Chemical compound with the Chemical formula of Ca[[Carbide C2]] g. LaC2. Lanthanum carbide ( La[[Carbon C2]] is a Chemical compound. It is manufactured through a process of diffusion and evaporation of Graphite [1] The C-C bond distance ranges from 109. 2pm in CaC2 (similar to ethyne), to 130. Calcium carbide is a Chemical compound with the Chemical formula of Ca[[Carbide C2]] 3 pm in LaC2 and 134pm in UC2. Lanthanum carbide ( La[[Carbon C2]] is a Chemical compound. It is manufactured through a process of diffusion and evaporation of Graphite Uranium carbide, a Carbide of Uranium, is a hard refractive Ceramic material [1] The bonding in LaC2 has been described in terms of LaIII with the extra electron delocalised into the antibonding orbital on C22−, explaining the metallic conduction. Lanthanum carbide ( La[[Carbon C2]] is a Chemical compound. It is manufactured through a process of diffusion and evaporation of Graphite [1]
Methanides
The monatomic ion C4− is a very strong base, and will combine with four protons to form methane. A monatomic ion is an Ion consisting of many ions of the same atoms The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Methanides commonly react with water to form methane, however reactions with other substances are common. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas.
C4− + 4H+ → CH4
Examples of compounds that contain C4− are Be2C and Al4C3. Aluminium carbide, chemical formula Al 4 C 3 is a Carbide of Aluminium. [1]
Sesquicarbides
The polyatomic ion C34− is found in e. A polyatomic ion is a charged species ( Ion) composed of two or more atoms covalently bonded or of a metal complex that can be considered as acting g. Li4C3, Mg2C3. Lithium carbide, Li2C2 often known as dilithium acetylide is a chemical compound of Lithium and Carbon. [1] The ion is linear and is isoelectronic with CO2. [1] The C-C distance in Mg2C3 is 133. 2 pm. [2] Mg2C3 yields methylacetylene, CH3CCH, on hydrolysis which was the first indication that it may contain C34−. Methylacetylene ( propyne) is an Alkyne with the Chemical formula H 3C≡CH
Covalent carbides
Silicon and boron form covalent carbides. [1] Silicon carbide has two similar crystalline forms, which are both related to the diamond structure. Silicon carbide ( is a compound of Silicon and Carbon bonded together to form Ceramics but it also occurs in nature as the extremely rare mineral [1] Boron carbide, B4C, on the other hand has an unusual structure which includes icosahedral boron units linked by carbon atoms. Boron carbide (chemical formula B4C is an extremely hard Ceramic material used in Tank Armor, Bulletproof vests and numerous In this respect boron carbide is similar to the boron rich borides. Boron carbide (chemical formula B4C is an extremely hard Ceramic material used in Tank Armor, Bulletproof vests and numerous In chemistry a boride is a chemical compound between boron and a less electronegative element Both silicon carbide, SiC, (carborundum) and boron carbide, B4C are very hard materials and refractory. Silicon carbide ( is a compound of Silicon and Carbon bonded together to form Ceramics but it also occurs in nature as the extremely rare mineral Boron carbide (chemical formula B4C is an extremely hard Ceramic material used in Tank Armor, Bulletproof vests and numerous A refractory is a material that retains its strength at high Temperatures ASTM C71 defines refractories as "non-metallic materials having those chemical and physical Both materials are important industrally. Boron also forms other covalent carbides, e. g. B25C.
Interstitial carbides
Properties
The carbides of the group 4, 5 and 6 transition metals (with the exception of chromium) are often described as interstitial compounds. The term interstitial compound, or interstitial alloy, is used to describe a compound that is formed when an atom of sufficiently small radius sits in an interstitial “hole” [1] These carbides are chemically quite inert, have metallic properties and are refractory. A refractory is a material that retains its strength at high Temperatures ASTM C71 defines refractories as "non-metallic materials having those chemical and physical Some exhibit a range of stoichiometries, e. g. titanium carbide, TiC. Titanium carbide, Ti[[Carbon C]] is an extremely hard ( Mohs 9-9 Titanium carbide and tungsten carbide are important industrially and are used to coat metals in cutting tools. Titanium carbide, Ti[[Carbon C]] is an extremely hard ( Mohs 9-9 Tungsten carbide, WC, or tungsten semicarbide, W2C, is a chemical compound containing Tungsten and Carbon, similar [3]
Structure
The longheld view is that the carbon atoms fit into octahedral interstices in a close packed metal lattice when the metal atom radius is greater than approximately 135 pm:[1]
- When the metal atoms are cubic close packed, (ccp), then filling all of the octahedral interstices with carbon achieves 1:1 stoichiometry with the rock salt structure, (note that in rock salt, NaCl, it is the chloride anions that are cubic close packed).
- When the metal atoms are hexagonal close packed, (hcp), as the octahedral interstices lie directly opposite each other on either side of the layer of metal atoms, filling only only one of these with carbon achieves 2:1 stoichiometry with the CdI2 structure.
The following table [1][3]shows actual structures of the metals and their carbides. (N. B. the body centred cubic structure adopted by vanadium, niobium, tantalum, chromium, molybdenum and tungsten is not a close packed lattice. ) The notation "h/2" refers to the M2C type structure described above, which is only an approximate description of the actual structures. The simple view that the lattice of the pure metal "absorbs" carbon atoms can be seen to be untrue as the packing of the metal atom lattice in the carbides is different from the packing in the pure metal.
| Metal | Structure of pure metal | Metallic radius (pm) |
MC - metal atom packing |
MC structure | M2C - metal atom packing |
M2C structure | Other carbides |
|---|---|---|---|---|---|---|---|
| titanium | hcp | 147 | ccp | rock salt | |||
| zirconium | hcp | 160 | ccp | rock salt | |||
| hafnium | hcp | 159 | ccp | rock salt | |||
| vanadium | cubic body centered | 134 | ccp | rock salt | hcp | h/2 | V4C3 |
| niobium | cubic body centered | 146 | ccp | rock salt | hcp | h/2 | Nb4C3 |
| tantalum | cubic body centered | 146 | ccp | rock salt | hcp | h/2 | Ta4C3 |
| chromium | cubic body centered | 128 | Cr23C6, Cr3C, Cr7C3, Cr3C2 |
||||
| molybdenum | cubic body centered | 139 | hexagonal | hcp | h/2 | Mo3C2 | |
| tungsten | cubic body centered | 139 | hexagonal | hcp | h/2 |
For a long time the non stoichiometric phases were believed to be disordered with a random filling of the interstices, however short and longer range ordering has been detected[4]. Titanium (taɪˈteɪniəm is a Chemical element with the symbol Ti and Atomic number 22 Zirconium (zɚˈkoʊniəm /ˌzɝˈkoʊniəm/ is a Chemical element with the symbol Zr and Atomic number 40 Hafnium (ˈhæfniəm is a Chemical element that has the symbol Hf and Atomic number 72 Vanadium (vəˈneɪdiəm is a Chemical element that has the symbol V and Atomic number 23 Niobium (naɪˈoʊbiəm or columbium (/kəˈlʌmbiəm/ is a Chemical element that has the symbol Nb and Atomic number 41 Tantalum (ˈtæntələm (formerly tantalium /tænˈtæliəm/ is a Chemical element with the symbol Ta and Atomic number 73 Chromium (ˈkroʊmiəm is a Chemical element which has the symbol Cr and Atomic number 24 Molybdenum (məˈlɪbdənəm from the Greek word for the metal " Lead " is a Group 6 Chemical element with the symbol Mo Tungsten (ˈtʌŋstən also known as wolfram (/ˈwʊlfrəm/ is a Chemical element that has the symbol W and Atomic number 74
Intermediate transition metal carbides
In these the transition metal ion is smaller than the critical 135 pm and the structures are not interstitial but are more complex. [1] Multiple stoichiometries are common, for example iron forms a number of carbides, Fe3C, Fe7C3 and Fe2C. [1] The best known is cementite, Fe3C, which is present in steels. Cementite or iron carbide is a Chemical compound with the formula Fe3C (or Fe2CFe and an Orthorhombic crystal structure [1] These carbides are more reactive than the interstitial carbides, for example the carbides of Cr, Mn, Fe, Co and Ni all are hydrolysed by dilute acids and sometimes by water, to give a mixture of hydrogen and hydrocarbons. [1] These compounds share features with both the inert interstitals and the more reactive salt-like carbides. [1]
References
- ^ a b c d e f g h i j k l m n o p q r s t u Greenwood, N. N. ; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.
- ^ Crystal Structure of Magnesium Sesquicarbide Fjellvag H. and Pavel K. Inorg. Chem. 1992, 31, 3260
- ^ a b Carbides: transition metal solid state chemistry Peter Ettmayer & Walter Lengauer, Encyclopedia of Inorganic Chemistry Editor in chief R. Bruce King Pub 1994 John Wiley & Sons ISBN 0-471-93620-0
- ^ Order and disorder in transition metal carbides and nitrides: experimental and theoretical aspects C. H. de Novion and J. P. Landesman Pure & Appl. Chem. , 57, 10,(1985)1391
Dictionary
carbide
-noun
- (chemistry) Any binary compound of carbon and a more electropositive element
- (chemistry) The polyatomic ion C22−, or any of its salts.
- (chemistry) The monatomic ion C4−, or any of its salts.
- (chemistry) A carbon-containing alloy or doping of a metal or semiconductor, such as steel.
- (chemistry) Tungsten carbide.
- (cycling) trivial name for calcium carbide (CaC2), used to produce acetylene in bicycle lamps in the early 1900s.
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