Magnesium nitride, which possesses the
chemical formula Mg
3N
2, is an
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistr ...
of
magnesium and
nitrogen. At room temperature and pressure it is a greenish yellow powder.
Preparation
* By passing dry nitrogen over heated magnesium:
::
* or ammonia:
::
History
When isolating
argon
Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...
,
William Ramsay
Sir William Ramsay (; 2 October 1852 – 23 July 1916) was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous elements ...
passed dry air over
copper to remove
oxygen and over
magnesium to remove the
nitrogen, forming magnesium nitride.
Chemistry
Magnesium nitride reacts with water to produce
magnesium hydroxide and
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
gas, as do many metal
nitrides.
:Mg
3N
2(s) + 6 H
2O
(l) → 3 Mg(OH)
2(aq) + 2 NH
3(g)
In fact, when magnesium is burned in air, some magnesium nitride is formed in addition to the principal product,
magnesium oxide
Magnesium oxide ( Mg O), or magnesia, is a white hygroscopic solid mineral that occurs naturally as periclase and is a source of magnesium (see also oxide). It has an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions ...
.
Thermal decomposition of magnesium nitride gives magnesium and nitrogen gas (at 700-1500 °C).
At high pressures, the stability and formation of new nitrogen-rich nitrides (N/Mg ratio equal or greater to one) were suggested and later discovered. These include the Mg
2N
4 and MgN
4 solids which both become thermodynamically stable near 50 GPa. The Mg
2N
4 is composed of exotic ''cis''-tetranitrogen N
44− species with N-N bond orders close to one. This Mg
2N
4 compound was recovered to ambient conditions, along with the N
44− units, marking only the fourth polynitrogen entity bulk stabilized at ambient conditions.
Uses
Magnesium nitride was the
catalyst
Catalysis () is the process of increasing the reaction rate, rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the ...
in the first practical synthesis of
borazon
Borazon is a brand name of a cubic form of boron nitride (cBN). Its color ranges from black to brown and gold, depending on the chemical bond. It is one of the hardest known materials, along with various forms of diamond and kinds of boron nitride ...
(cubic
boron nitride
Boron nitride is a thermally and chemically resistant refractory compound of boron and nitrogen with the chemical formula BN. It exists in various crystalline forms that are isoelectronic to a similarly structured carbon lattice. The hexagon ...
).
Robert H. Wentorf, Jr. was trying to convert the hexagonal form of boron nitride into the cubic form by a combination of heat, pressure, and a catalyst. He had already tried all the logical catalysts (for instance, those that catalyze the synthesis of
diamond), but with no success.
Out of desperation and curiosity (he called it the "make the maximum number of mistakes" approach
), he added some magnesium wire to the hexagonal boron nitride and gave it the same pressure and heat treatment. When he examined the wire under a microscope, he found tiny dark lumps clinging to it. These lumps could scratch a polished block of
boron carbide
Boron carbide (chemical formula approximately B4C) is an extremely hard boron– carbon ceramic, a covalent material used in tank armor, bulletproof vests, engine sabotage powders,
as well as numerous industrial applications. With a Vickers ...
, something only diamond was known to do.
From the smell of ammonia, caused by the reaction of magnesium nitride with the moisture in the air, he deduced that the magnesium metal had reacted with the boron nitride to form magnesium nitride, which was the true catalyst.
References
Further reading
*
{{DEFAULTSORT:Magnesium Nitride
Nitrides
Magnesium compounds