In
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, a nitride is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
of
nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
. Nitrides can be
inorganic
An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bondsthat is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemistry''.
Inor ...
or
organic,
ionic or
covalent
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...
. The nitride
anion
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
, N
3−, is very elusive but compounds of nitride are numerous, although rarely naturally occurring. Some nitrides have a found applications, such as
wear
Wear is the damaging, gradual removal or deformation of material at solid surfaces. Causes of wear can be mechanical (e.g., erosion) or chemical (e.g., corrosion). The study of wear and related processes is referred to as tribology.
Wear in ...
-resistant
coating
A coating is a covering that is applied to the surface of an object, or substrate. The purpose of applying the coating may be decorative, functional, or both. Coatings may be applied as liquids, gases or solids e.g. powder coatings.
Paints ...
s (e.g.,
titanium nitride, TiN), hard
ceramic materials (e.g.,
silicon nitride, Si
3N
4), and
semiconductor
A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...
s (e.g.,
gallium nitride, GaN). The development of GaN-based
light emitting diodes was recognized by the 2014
Nobel Prize in Physics
The Nobel Prize in Physics () is an annual award given by the Royal Swedish Academy of Sciences for those who have made the most outstanding contributions to mankind in the field of physics. It is one of the five Nobel Prizes established by the ...
.
Metal nitrido complexes are also common.
Synthesis of inorganic metal nitrides is challenging because nitrogen gas (N
2) is not very reactive at low temperatures, but it becomes more reactive at higher temperatures. Therefore, a balance must be achieved between the low reactivity of nitrogen gas at low temperatures and the
entropy
Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the micros ...
driven formation of N
2 at high temperatures. However, synthetic methods for nitrides are growing more sophisticated and the materials are of increasing technological relevance.
Uses of nitrides
Like
carbide
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
Interstitial / Metallic carbides
The carbides of th ...
s, nitrides are often
refractory materials owing to their high
lattice energy
In chemistry, the lattice energy is the energy change (released) upon formation of one mole of a crystalline compound from its infinitely separated constituents, which are assumed to initially be in the gaseous state at 0 K. It is a measure of ...
, which reflects the strong bonding of "N
3−" to metal cation(s). Thus,
cubic boron nitride,
titanium nitride, 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
In solid-state physics and solid-state chemistry, a band gap, also called a bandgap or energy gap, is an energy range in a solid where no electronic states exist. In graphs of the electronic band structure of solids, the band gap refers to t ...
s, thus nitrides are usually
insulators or
wide-bandgap semiconductors; examples include
boron nitride and silicon nitride. The wide-band gap material
gallium nitride is prized for emitting blue light in
LEDs. Like some oxides, nitrides can absorb hydrogen and have been discussed in the context of
hydrogen storage, e.g.
lithium nitride
Lithium nitride is an inorganic compound with the chemical formula . It is the only stable alkali metal nitride. It is a reddish-pink solid with a high melting point.
Preparation and handling
Lithium nitride is prepared by direct reaction of ele ...
.
Examples
Classification of such a varied group of compounds is somewhat arbitrary. Compounds where nitrogen is not assigned −3 oxidation state are not included, such as
nitrogen trichloride where the oxidation state is +3; nor are
ammonia
Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...
and its many organic derivatives.
Nitrides of the s-block elements
Only one
alkali metal
The alkali metals consist of the chemical elements lithium (Li), sodium (Na), potassium (K),The symbols Na and K for sodium and potassium are derived from their Latin names, ''natrium'' and ''kalium''; these are still the origins of the names ...
nitride is stable, the purple-reddish
lithium nitride
Lithium nitride is an inorganic compound with the chemical formula . It is the only stable alkali metal nitride. It is a reddish-pink solid with a high melting point.
Preparation and handling
Lithium nitride is prepared by direct reaction of ele ...
(), which forms when lithium burns in an atmosphere of . Both
Sodium nitride and
potassium nitride have been synthesized, but remain a laboratory curiosity. The nitrides of the
alkaline earth metal
The alkaline earth metals are six chemical elements in group (periodic table), group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar p ...
s that have the formula are however numerous. Examples include
beryllium nitride (),
magnesium nitride (),
calcium nitride (), and
strontium nitride (). The nitrides of electropositive metals (including Li, Zn, and the alkaline earth metals) readily hydrolyze upon contact with water, including the moisture in the air:
:
Nitrides of the p-block elements
Boron nitride exists as several forms (
polymorphs). Nitrides of
silicon
Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...
and phosphorus are also known, but only the former is commercially important. The nitrides of
aluminium
Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...
,
gallium
Gallium is a chemical element; it has Chemical symbol, symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875,
elemental gallium is a soft, silvery metal at standard temperature and pressure. ...
, and
indium
Indium is a chemical element; it has Symbol (chemistry), symbol In and atomic number 49. It is a silvery-white post-transition metal and one of the softest elements. Chemically, indium is similar to gallium and thallium, and its properties are la ...
adopt the hexagonal
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 (named in honour of Kathleen Lonsdale), also called hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice, as opposed to the cubical lattice of conventional diamond. It is found ...
) where every carbon atom occupies a tetrahedral site (however wurtzite differs from
sphalerite
Sphalerite is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimentary exhalative, Carbonate-hoste ...
and
diamond
Diamond is a Allotropes of carbon, solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Diamond is tasteless, odourless, strong, brittle solid, colourless in pure form, a poor conductor of e ...
in the relative orientation of tetrahedra).
Thallium(I) nitride () is known, but thallium(III) nitride (TlN) is not.
Transition metal nitrides
Most metal-rich transition metal nitrides adopt a relatively ordered
face-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties o ...
or
hexagonal close-packed crystal structure, with octahedral coordination. Sometimes these materials are called "
interstitial nitrides". They are essential for industrial
metallurgy
Metallurgy is a domain of materials science and engineering that studies the physical and chemical behavior of metallic elements, their inter-metallic compounds, and their mixtures, which are known as alloys.
Metallurgy encompasses both the ...
, because they are typically much
harder and less
ductile
Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...
than their parent metal, and resist air-oxidation. For the
group 3 Group 3 may refer to:
* Group 3 element, chemical element classification
* Group 3 (motorsport), FIA classification of cars used in auto racing and rallying
* Group 3, the third tier of races in worldwide Thoroughbred horse racing
* Group 3 image ...
metals, ScN and
YN are both known.
Group 4 Group 4 may refer to:
*Group 4 element
Group 4 is the second group of transition metals in the periodic table. It contains only the four elements titanium (Ti), zirconium (Zr), hafnium (Hf), and rutherfordium (Rf). The group is also called the t ...
,
5, and
6 transition metals (the titanium, vanadium and chromium groups) all form chemically stable,
refractory
In materials science, a refractory (or refractory material) is a material that is resistant to decomposition by heat or chemical attack and that retains its strength and rigidity at high temperatures. They are inorganic, non-metallic compound ...
nitrides with high melting point.
Thin film
A thin film is a layer of materials ranging from fractions of a nanometer ( monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many ...
s of
titanium nitride,
zirconium nitride, and
tantalum nitride protect many industrial surfaces.
Nitrides of the
group 7 Group 7 may refer to:
* G7, an international group of finance minister
*Group 7 element, chemical element classification
*Halogens
The halogens () are a group (periodic table), group in the periodic table consisting of six chemically related c ...
and
8 transition metals tend to be nitrogen-poor, and decompose readily at elevated temperatures. For example,
iron nitride, decomposes at 200 °C. Platinum nitride and osmium nitride may contain units, and as such should not be called nitrides.
Nitrides of heavier members from group
11 and
12 are less stable than
copper nitride () and
zinc nitride (): dry
silver nitride () is a
contact explosive which may detonate from the slightest touch, even a falling water droplet.
Nitrides of the lanthanides and actinides
Nitride containing species of the lanthanides and actinides are of scientific interest as they can provide a useful handle for determining covalency of bonding. Nuclear magnetic resonance (NMR) spectroscopy along with quantum chemical analysis has often been used to determine the degree to which metal nitride bonds are ionic or covalent in character. One example, a uranium nitride, has the highest known nitrogen-15 chemical shift.
Molecular nitrides
Many metals form molecular nitrido complexes, as discussed in the specialized article. The
main group element
In chemistry and atomic physics, the main group is the group (periodic table), group of chemical element, elements (sometimes called the representative elements) whose lightest members are represented by helium, lithium, beryllium, boron, carbon ...
s also form some molecular nitrides.
Cyanogen
Cyanogen is the chemical compound with the chemical formula, formula . Its structure is . The simplest stable carbon nitride, it is a Transparency and translucency, colorless and highly toxic gas with a pungency, pungent odor. The molecule is a ...
() and
tetrasulfur tetranitride () are rare examples of a molecular binary (containing one element aside from nitrogen) nitrides. They dissolve in nonpolar solvents. Both undergo polymerization. is also unstable with respect to the elements, but less so that the isostructural . Heating gives a polymer, and a variety of molecular sulfur nitride anions and cations are also known.
Related to but distinct from nitride is
pernitride diatomic anion () and the
azide
In chemistry, azide (, ) is a linear, polyatomic anion with the formula and structure . It is the conjugate base of hydrazoic acid . Organic azides are organic compounds with the formula , containing the azide functional group. The dominant ...
triatomic anion (N
3−).
References
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it is Nitride
Anions
Nitrides