Sodium nitride

Not to be confused with sodium nitrate, sodium nitrite, or sodium azide.

Sodium nitride

Names
IUPAC name Sodium nitride
Identifiers
CAS Number	12136-83-3  Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.032.017
EC Number	235-232-3
InChI InChI=1/3Na.N Key: ZOULLXMSYSKRPG-UHFFFAOYNA-N
SMILES [Na+].[Na+].[Na+].[N-3]
Properties
Chemical formula	Na3N
Molar mass	82.976 g/mol
Appearance	reddish brown or dark blue solid
Melting point	104 °C (219 °F; 377 K) [1] (decomposes)
Solubility in water	reacts
Structure
Crystal structure	Cubic, cP4 [2]
Space group	Pm3m [2]
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	-151 J/mol [2]
Related compounds
Other anions	Sodium amide Sodium imide
Other cations	Lithium nitride Potassium nitride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y  verify  (what is  YN ?) Infobox references

Sodium nitride is the inorganic compound with the chemical formula Na₃N. In contrast to lithium nitride and some other nitrides, sodium nitride is unstable. It readily decomposes into its elements: ^[3]

2 Na₃N → 6 Na + N₂

It can be generated by various methods. The instability of sodium nitride is relevant to the mechanism of action of sodium azide in airbags:

2 NaN₃N → 2 Na + 3 N₂

Synthesis

It can be generated by combining atomic beams of sodium and nitrogen deposited onto a low-temperature sapphire substrate ^[3] or a metal surface. This synthesis can be further facilitated by introducing liquid Na-K alloy to the compound with the excess liquid removed and washed with fresh alloy. The solid is then separated from the liquid using a centrifuge. However Vajenine’s method is very air-sensitive and can decompose and combust rapidly, so an argon environment is used. ^[1]

Sodium nitride can be generated also by the thermal decomposition of NaNH₂. ^[2]

Characteristics

Sodium nitride can be of reddish brown or dark blue color depending on the synthetic method. ^{[3] [1]} It shows no signs of decomposition after several weeks when at room temperature. ^[1] The compound does not have a melting point as it decomposes back into its elemental forms as demonstrated using mass spectrometry around 360 K. ^{[3] [2]} The estimated enthalpy of formation for the compound is +64 kJ/mol. ^[1]

Structure

Sodium nitride seems to be about 90% ionic at room temperature, but has the band gap typical for a semiconductor. ^{[2] [1]} It adopts the anti-ReO₃ structure with a simple lattice made up of NNa₆ octahedra. ^{[3] [2] [1] [4]} The compound has N−Na bond lengths of 236.6 pm. ^{[3] [1]} This structure has been confirmed through X-ray diffraction and more recently neutron diffraction on powder and single crystals. ^{[3] [2] [1] [4]}

References

1. Vajenine, G.V. (2007). "Plasma-Assisted Synthesis and Properties of Na₃N". Inorganic Chemistry. 46 (13): 5146–5148. doi:10.1021/ic700406q. PMID   17530752.
2. Sangster, J. (2004). "N-Na(Nitrogen-Sodium) System". Journal of Phase Equilibria and Diffusion. 25 (6): 560–563. Bibcode:2004JPED...25..560S. doi:10.1007/s11669-004-0082-0. S2CID   97905377.
3. Fischer, D., Jansen, M. (2002). "Synthesis and structure of Na₃N". Angew Chem. 41 (10): 1755–1756. doi:10.1002/1521-3773(20020517)41:10<1755::AID-ANIE1755>3.0.CO;2-C. PMID   19750706.Fischer, D.; Cancarevic, Z.; Schön, J. C.; Jansen, M. Z. (2004). "Synthesis and structure of K₃N". Z. Anorg. Allg. Chem. 630 (1): 156. doi:10.1002/zaac.200300280.. 'Elusive Binary Compound Prepared' Chemical & Engineering News80 No. 20 (20 May 2002)
4. Vajenine, G. V., Hoch, C., Dinnebier, R. E., Senyshyn, A., Niewa, R. (2009). "A Temperature-dependent Structural Study of anti-ReO₃-type Na₃N: to Distort or not to Distort?". Zeitschrift für Anorganische und Allgemeine Chemie. 636 (1): 94–99. doi:10.1002/zaac.200900488.