Nitride
Encyclopedia
In chemistry
, a nitride is a compound of nitrogen
where nitrogen has a formal oxidation state
of −3. Nitrides are a large class of compounds with a wide range of properties and applications.
The nitride ion, N3–, is never encountered in solution because it is so basic that it would be protonated. Its ionic radius is estimated to be 140 pm. Related to but distinct from nitride is pernitride, N22–.
and silicon nitride
are used as cutting materials and hard coatings. Hexagonal boron nitride
, which adopts a layered structure, is a useful high-temperature lubricant akin to molybdenum disulfide
. Nitride compounds often have large band gap
s, thus nitrides are usually insulators, examples include boron nitride
and silicon nitride. The wide band gap material gallium nitride is prized for emitting blue light in LED
s. Like some oxides, nitrides can absorb hydrogen and have been discussed in the context of hydrogen storage, e.g. lithium nitride
.
, nor are ammonia and its many organic derivatives.
(Li3N), which forms when lithium burns in an atmosphere of N2. Sodium nitride
and potassium nitride have been generated in the laboratory, however. The nitrides of the alkali earth metals have the formula M3N2 and are numerous. Examples include Mg3N2
, Be3N2
, Ca3N2
, Sr3N2
, and Ba3N2. The nitrides of electropositive metals (Li, alkali metals Zn) readily hydrolyze upon contact with air:
s). Nitrides of silicon and phosphorus are also known, but only the former is commercially important. The nitrides of aluminium
, gallium, and indium adopt diamond-like wurtzite structure in which each atom occupies tetrahedral sites. For example in aluminium nitride, each aluminium atom has four neighboring nitrogen atoms at the corners of a tetrahedron and similarly each nitrogen atom has four neighboring aluminium atoms at the corners of a tetrahedron. This structure is like hexagonal diamond (lonsdaleite
) where every carbon atom occupies a tetrahedral site (however wurtzite differs from sphalerite
and diamond
in the relative orientation of tetrahedra). Thallium(I) nitride, Tl3N is known, but thallium(III) nitride, TlN, is not.
metals, scandium nitride (ScN) is known. group 4
, 5
, and 6
transition metals, that is the titanium, vanadium and chromium groups all form nitrides. They are refractory
, with high melting point and are chemically stable. Representative is titanium nitride
. Sometimes these materials are called "interstial
nitrides."
Nitrides of the Group 7
and 8
transition metals decompose readily. For example, iron nitride
, Fe2N decomposes at 200 °C. Platinum nitride and osmium nitride may contain N2 units, and as such should not be called nitrides.
The group 11
metals e.g. copper nitride, Cu3N and the group 12
metals e.g. Zn3N2
.
s also form some molecular nitrides. Cyanogen
((CN)2) and tetrasulfur tetranitride
(S4N4) are rare examples of a molecular binary (containing one element aside from N) nitrides. They dissolve in nonpolar solvents. Both undergo polymerization. S4N4 is also unstable with respect to the elements, but less so that the isostructural Se4N4. Heating S4N4 gives a polymer, and a variety of molecular sulfur nitride anions and cations are also known.
Chemistry
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds....
, a nitride is a compound of nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
where nitrogen has a formal oxidation state
Oxidation state
In chemistry, the oxidation state is an indicator of the degree of oxidation of an atom in a chemical compound. The formal oxidation state is the hypothetical charge that an atom would have if all bonds to atoms of different elements were 100% ionic. Oxidation states are typically represented by...
of −3. Nitrides are a large class of compounds with a wide range of properties and applications.
The nitride ion, N3–, is never encountered in solution because it is so basic that it would be protonated. Its ionic radius is estimated to be 140 pm. Related to but distinct from nitride is pernitride, N22–.
Uses of nitrides
Like carbides, nitrides are often refractory materials owing to their high lattice energy which reflects the strong attraction of "N3-" for the metal cation. Thus, titanium nitrideTitanium nitride
Titanium nitride is an extremely hard ceramic material, often used as a coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties....
and silicon nitride
Silicon nitride
Silicon nitride is a chemical compound of silicon and nitrogen. If powdered silicon is heated between 1300° and 1400°C in an atmosphere of nitrogen, trisilicon tetranitride, Si3N4, is formed. The silicon sample weight increases progressively due to the chemical combination of silicon and nitrogen...
are used as cutting materials and hard coatings. Hexagonal boron nitride
Boron nitride
Boron nitride is a chemical compound with chemical formula BN, consisting of equal numbers of boron and nitrogen atoms. BN is isoelectronic to a similarly structured carbon lattice and thus exists in various crystalline forms...
, which adopts a layered structure, is a useful high-temperature lubricant akin to molybdenum disulfide
Molybdenum disulfide
Molybdenum disulfide is the inorganic compound with the formula MoS2. This black crystalline sulfide of molybdenum occurs as the mineral molybdenite. It is the principal ore from which molybdenum metal is extracted. The natural amorphous form is known as the rarer mineral jordisite. MoS2 is less...
. Nitride compounds often have large band gap
Band gap
In solid state physics, a band gap, also called an energy gap or bandgap, is an energy range in a solid where no electron states can exist. In graphs of the electronic band structure of solids, the band gap generally refers to the energy difference between the top of the valence band and the...
s, thus nitrides are usually insulators, examples include boron nitride
Boron nitride
Boron nitride is a chemical compound with chemical formula BN, consisting of equal numbers of boron and nitrogen atoms. BN is isoelectronic to a similarly structured carbon lattice and thus exists in various crystalline forms...
and silicon nitride. The wide band gap material gallium nitride is prized for emitting blue light in LED
LEd
LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....
s. Like some oxides, nitrides can absorb hydrogen and have been discussed in the context of hydrogen storage, e.g. lithium nitride
Lithium nitride
Lithium nitride is a compound of lithium and nitrogen with the formula Li3N. It is the only stable alkali metal nitride...
.
Examples
Classification of such a varied group of compounds is somewhat arbitrary. Compounds where nitrogen is not assigned 3- oxidation state are not included, e.g. nitrogen trichlorideNitrogen trichloride
Nitrogen trichloride, also known as trichloramine, is the chemical compound with the formula NCl3. This yellow, oily, pungent-smelling liquid is most commonly encountered as a byproduct of chemical reactions between ammonia-derivatives and chlorine .In pure form, NCl3 is highly reactive...
, nor are ammonia and its many organic derivatives.
Nitrides of the s-block elements
Only one alkali metal nitride is stable, the purple-reddish lithium nitrideLithium nitride
Lithium nitride is a compound of lithium and nitrogen with the formula Li3N. It is the only stable alkali metal nitride...
(Li3N), which forms when lithium burns in an atmosphere of N2. Sodium nitride
Sodium nitride
Sodium nitride is the inorganic compound with the formula Na3N. In contrast to lithium nitride and many other nitrides, sodium nitride is an extremely unstable alkali metal nitride...
and potassium nitride have been generated in the laboratory, however. The nitrides of the alkali earth metals have the formula M3N2 and are numerous. Examples include Mg3N2
Magnesium nitride
Magnesium nitride, which has the chemical formula Mg3N2, is an inorganic compound of magnesium and nitrogen. At room temperature and pressure it is a greenish yellow powder.-Chemistry:...
, Be3N2
Beryllium nitride
Beryllium nitride, Be3N2, is a nitride of beryllium. It can be prepared from the elements at high temperature , different Beryllium azide or BeN6,it decomposes in vacuum into beryllium and nitrogen. It is readily hydrolysed forming beryllium hydroxide and ammonia. It has two polymorphic forms cubic...
, Ca3N2
Calcium nitride
Calcium nitride is a red-brown, crystalline solid made up of calcium and nitrogen. Its chemical formula is Ca3N2.α-Calcium nitride is the commonly encountered form...
, Sr3N2
Strontium nitride
Strontium nitride, Sr3N2, is produced by burning strontium metal in air or in nitrogen. Like other metal nitrides, it reacts with water to give strontium hydroxide and ammonia:...
, and Ba3N2. The nitrides of electropositive metals (Li, alkali metals Zn) readily hydrolyze upon contact with air:
- 2 Mg4N3 + 9 H2O → 8 MgO + 6 NH3
Nitrides of the p-block elements
Boron nitride exists as several forms (polymorphPolymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
s). Nitrides of silicon and phosphorus are also known, but only the former is commercially important. The nitrides of aluminium
Aluminium nitride
Aluminium nitride is a nitride of aluminium. Its wurtzite phase is a wide band gap semiconductor material, giving it potential application for deep ultraviolet optoelectronics.-History:...
, gallium, and indium adopt diamond-like wurtzite structure in which each atom occupies tetrahedral sites. For example in aluminium nitride, each aluminium atom has four neighboring nitrogen atoms at the corners of a tetrahedron and similarly each nitrogen atom has four neighboring aluminium atoms at the corners of a tetrahedron. This structure is like hexagonal diamond (lonsdaleite
Lonsdaleite
Lonsdaleite , also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice. In nature, it forms when meteorites containing graphite strike the Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains...
) where every carbon atom occupies a tetrahedral site (however wurtzite differs from sphalerite
Sphalerite
Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...
and diamond
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
in the relative orientation of tetrahedra). Thallium(I) nitride, Tl3N is known, but thallium(III) nitride, TlN, is not.
Transition metal nitrides
For the group 3Group 3 element
The group 3 elements are a group of chemical elements in the periodic table. This group, like other d-block groups, should contain four elements, but it is not agreed what elements belong in the group...
metals, scandium nitride (ScN) is known. group 4
Group 4 element
The Group 4 elements are a group of chemical elements in the periodic table. In the modern IUPAC nomenclature, Group 4 of the periodic table contains titanium , zirconium , hafnium and rutherfordium . This group lies in the d-block of the periodic table...
, 5
Group 5 element
A Group 5 element is a chemical element in the fifth group in the periodic table. In the modern IUPAC nomenclature, Group 5 of the periodic table contains vanadium , niobium , tantalum and dubnium . This group lies in the d-block of the periodic table...
, and 6
Group 6 element
A Group 6 element is one in the series of elements in group 6 in the periodic table, which consists of the transition metals chromium , molybdenum , tungsten , and seaborgium ....
transition metals, that is the titanium, vanadium and chromium groups all form nitrides. They are refractory
Refractory
A refractory material is one that retains its strength at high temperatures. ASTM C71 defines refractories as "non-metallic materials having those chemical and physical properties that make them applicable for structures, or as components of systems, that are exposed to environments above...
, with high melting point and are chemically stable. Representative is titanium nitride
Titanium nitride
Titanium nitride is an extremely hard ceramic material, often used as a coating on titanium alloys, steel, carbide, and aluminium components to improve the substrate's surface properties....
. Sometimes these materials are called "interstial
Interstitial defect
Interstitials are a variety of crystallographic defects, i.e. atoms which occupy a site in the crystal structure at which there is usually not an atom, or two or more atoms sharing one or more lattice sites such that the number of atoms is larger than the number of lattice sites.They are generally...
nitrides."
Nitrides of the Group 7
Group 7 element
A Group 7 element is one in the series of elements in group 7 in the periodic table, which consists of manganese , technetium , rhenium , and bohrium...
and 8
Group 8 element
A Group 8 element is one in the series of elements in group 8 in the periodic table, which consists of the transition metals iron , ruthenium , osmium and hassium ....
transition metals decompose readily. For example, iron nitride
Iron nitride
- Chemical properties:Iron has four nitrides, Fe2N, Fe3N1+x, Fe4N, and Fe16N2. They are crystalline, metallic solids. Group VII and group VIII transition metals form nitrides that decompose at relatively low temperatures - iron nitride, Fe2N decomposes under loss of molecular nitrogen at about...
, Fe2N decomposes at 200 °C. Platinum nitride and osmium nitride may contain N2 units, and as such should not be called nitrides.
The group 11
Group 11 element
A Group 11 element is one in the series of elements in group 11 in the periodic table, consisting of transition metals which are the traditional coinage metals of copper , silver , and gold...
metals e.g. copper nitride, Cu3N and the group 12
Group 12 element
A group 12 element is one of the elements in group 12 in the periodic table. This includes zinc , cadmium and mercury . The further inclusion of copernicium in group 12 is supported by recent experiments on individual Cn atoms...
metals e.g. Zn3N2
Zinc nitride
Zinc nitride is an inorganic compound of zinc and nitrogen. In pure form, it is cubic in structure.-Chemical properties:Zinc nitride can be obtained by thermally decomposing zincamide...
.
Molecular nitrides
Many metals form molecular nitrido complexes, as discussed in the specialized article. The main group elementMain group element
In chemistry and atomic physics, main group elements are elements in groups whose lightest members are represented by helium, lithium,...
s also form some molecular nitrides. Cyanogen
Cyanogen
Cyanogen is the chemical compound with the formula 2. It is a colorless, toxic gas with a pungent odor.The molecule is a pseudohalogen. Cyanogen molecules consist of two CN groups — analogous to diatomic halogen molecules, such as Cl2, but far less oxidizing...
((CN)2) and tetrasulfur tetranitride
Tetrasulfur tetranitride
Tetrasulfur tetranitride is an inorganic compound with the formula S4N4. This gold-poppy coloured solid is the most important binary sulfur nitride, which are compounds that contain only the elements sulfur and nitrogen. It is a precursor to many S-N compounds and has attracted wide interest for...
(S4N4) are rare examples of a molecular binary (containing one element aside from N) nitrides. They dissolve in nonpolar solvents. Both undergo polymerization. S4N4 is also unstable with respect to the elements, but less so that the isostructural Se4N4. Heating S4N4 gives a polymer, and a variety of molecular sulfur nitride anions and cations are also known.