Lithium nitride
Encyclopedia
Lithium nitride is a compound
of lithium
and nitrogen
with the formula
Li3N. It is the only stable alkali metal
nitride. The solid is a red or purple color and has a high melting point.
Li3N has an unusual crystal structure that consists of two types of layers, one sheet has the composition Li2N− contains 6-coordinate Li centers and the other sheet consists only of lithium cations. Solid lithium nitride is a fast ion conductor
and has the highest conductivity of any inorganic lithium salt. It has been studied extensively as a solid electrolyte and an anode material for use in batteries. It can be formed by direct reaction of the elements, either by burning lithium metal in pure nitrogen gas or by reacting nitrogen gas with lithium dissolved in liquid sodium
metal. The second method gives a purer product. Lithium nitride reacts violently with water
to produce ammonia
:
Other alkali and alkaline earth nitrides also react in this manner, due to the high basicity of the nitride. The hypothetical nitride ion, N3−, would be an extremely strong Brønsted base
, easily qualifying as a superbase
. It is, in fact, a stronger base than the hydride
ion, and so deprotonates hydrogen
itself:
Lithium nitride is being investigated as a potential storage medium
for hydrogen
gas, as the reaction is reversible at 270 °C. Up to 11.5% by weight absorption of hydrogen has been achieved.
Lithium nitride reacts with air to make lithium oxide, lithium hydroxide, and lithium carbonate.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
of lithium
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
and 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...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
Li3N. It is the only stable alkali metal
Alkali metal
The alkali metals are a series of chemical elements in the periodic table. In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, along with hydrogen. The alkali metals are lithium , sodium , potassium , rubidium , caesium , and francium...
nitride. The solid is a red or purple color and has a high melting point.
Li3N has an unusual crystal structure that consists of two types of layers, one sheet has the composition Li2N− contains 6-coordinate Li centers and the other sheet consists only of lithium cations. Solid lithium nitride is a fast ion conductor
Fast ion conductor
In solid-state ionics, fast ion conductors, also known as solid electrolytes and superionic conductors, are materials that act as solid state ion conductors and are used primarily in solid oxide fuel cells. As solid electrolytes they conduct due to the movement of ions through voids, or empty...
and has the highest conductivity of any inorganic lithium salt. It has been studied extensively as a solid electrolyte and an anode material for use in batteries. It can be formed by direct reaction of the elements, either by burning lithium metal in pure nitrogen gas or by reacting nitrogen gas with lithium dissolved in liquid sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
metal. The second method gives a purer product. Lithium nitride reacts violently with water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
to produce ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
:
- Li3N (s) + 3 H2O (l) → 3 LiOH (aq) + NH3 (g)
Other alkali and alkaline earth nitrides also react in this manner, due to the high basicity of the nitride. The hypothetical nitride ion, N3−, would be an extremely strong Brønsted base
Base (chemistry)
For the term in genetics, see base A base in chemistry is a substance that can accept hydrogen ions or more generally, donate electron pairs. A soluble base is referred to as an alkali if it contains and releases hydroxide ions quantitatively...
, easily qualifying as a superbase
Superbase
In chemistry, a superbase is an extremely strong base, that is a compound that has a high affinity for protons. Hydroxide ion is the strongest base possible in aqueous solutions, but bases exist with pKb's well outside of the aqueous range. Such bases are valuable in organic synthesis and are...
. It is, in fact, a stronger base than the hydride
Hydride
In chemistry, a hydride is the anion of hydrogen, H−, or, more commonly, a compound in which one or more hydrogen centres have nucleophilic, reducing, or basic properties. In compounds that are regarded as hydrides, hydrogen is bonded to a more electropositive element or group...
ion, and so deprotonates hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
itself:
- Li3N (s) + 2 H2 (g) → LiNH2 (s) + 2 LiH (s)
Lithium nitride is being investigated as a potential storage medium
Hydrogen storage
Hydrogen storage describes the methods for storing H2 for subsequent use. The methods span many approaches, including high pressures, cryogenics, and chemical compounds that reversibly release H2 upon heating...
for hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
gas, as the reaction is reversible at 270 °C. Up to 11.5% by weight absorption of hydrogen has been achieved.
Lithium nitride reacts with air to make lithium oxide, lithium hydroxide, and lithium carbonate.