Binary compounds of hydrogen
Binary compounds of hydrogen are binary chemical compounds containing just hydrogen and one other chemical element. By convention all binary hydrogen compounds are called hydrides even when the hydrogen atom in it is not an anion.[1][2][3][4] These hydrogen compounds can be grouped into several types.
Binary hydrogen compounds in group 1 are the ionic hydrides (also called saline hydrides) wherein hydrogen is bound electrostatically. Because hydrogen is located somewhat centrally in a electronegative sense, it is necessary for the counterion to be exceptionally electropositive for the hydride to possibly be accurately described as truly behaving ionic. Therefore, this category of hydrides contains only a few members.
Hydrides in group 2 are polymeric covalent hydrides. In these, hydrogen forms bridging covalent bonds, usually possessing mediocre degrees of ionic character, which make them difficult to be accurately described as either covalent or ionic. The one exception is beryllium hydride, which has definitively covalent properties.
Hydrides in the transition metals and Lanthanoids are also typically polymeric covalent hydrides. However, they usually possess only weak degrees of ionic character. Usually, these hydrides rapidly decompose into their component elements at ambient conditions. The results consist of metallic matrices with dissolved, often stoichiometric or near so, concentrations of hydrogen, ranging from negligible to substantial. Such a solid can be thought of as a solid solution and is alternately termed a metallic- or interstitial hydride. These decomposed solids are identifiable by their ability to conduct electricity and their magnetic properties (the presence of hydrogen is coupled with the delocalisation of the valence electrons of the metal), and their lowered density compared to the metal. Both the saline hydrides and the polymeric covalent hydrides typically react strongly with water and air.
It is possible to produce a metallic hydride without requiring decomposition as a necessary step. If a sample of bulk metal is subjected to any one of numerous hydrogen absorption techniques, the characteristics, such as luster and hardness of the metal is often retained to a large degree. Bulk actinoid hydrides are only known in this form. The affinity for hydrogen for most of the d-block elements are low. Therefore elements in this block do not form hydrides (the hydride gap) under standard temperature and pressure with the notable exception of palladium.[5] Palladium can absorb up to 900 times its own volume of hydrogen and is therefore actively researched in the field hydrogen storage.
Elements in group 13 to 17 (p-block) form covalent hydrides (or nonmetal hydrides). In group 12 zinc hydride is a common chemical reagent but cadmium hydride and mercury hydride are very unstable and esoteric. In group 13 boron hydrides exist as a highly reactive monomer BH3, as an adduct for example ammonia borane or as dimeric diborane and as a whole group of BH cluster compounds. Alane (AlH3) is a polymer. Gallium exists as the dimer digallane. Indium hydride is only stable below −90 °C (−130 °F).
In group 14 the total number of possible binary saturated compounds with carbon of the type CnH2n+2 is very large. Going down the group the number of binary silicon compounds (silanes) is small (straight or branched but rarely cyclic) for example disilane and trisilane. For germanium only 5 linear chain binary compounds are known as gases or volatile liquids. Examples are n-pentagermane, isopentagermane and neopentagermane. Of tin only the distannane is known. Plumbane is an unstable gas.
Non-classical hydrides are those in which extra hydrogen molecules are coordinated as a ligand on the central atoms. These are very unstable but some have been shown to exist.
The periodic table of the stable binary hydrides
The relative stability of binary hydrogen compounds and alloys at standard temperature and pressure can be inferred from their standard enthalpy of formation values.[6]
H2 0 | He | ||||||||||||||||
LiH -91 | BeH2 125 | BH3 91 | CH4 -74.8 | NH3 -46.8 | H2O -243 | HF -272 | Ne | ||||||||||
NaH -57 | MgH2 -75 | AlH3 | SiH4 -31 | PH3 5.4 | H2S -207 | HCl -93 | Ar | ||||||||||
KH -58 | CaH2 -174 | ScH3 | TiH1.7 | VH | CrH | Mn | Fe | Co | Ni | CuH | ZnH2 | GaH3 | GeH4 92 | AsH3 67 | H2Se 30 | HBr -36.5 | Kr |
RbH -47 | SrH2 -177 | YH3 | ZrH2 | NbHx | Mo | Tc | Ru | Rh | PdH | Ag | CdH2 | InH3 | SnH4 163 | SbH3 146 | H2Te 100 | HI 26.6 | Xe |
CsH -50 | BaH2 -172 | HfH2 | TaH | W | Re | Os | Ir | Pt | Au | HgH | Tl | PbH4 252 | BiH3 277 | H2Po | At | Rn | |
Fr | Ra | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Uut | Uuq | Uup | Uuh | Uus | Uuo | |
↓ | |||||||||||||||||
LaH2 | CeH2 | PrH2 | NdH2 | PmH2 | SmH2 | EuH2 | GdH2 | TbH2 | DyH2 | HoH2 | ErH2 | TmH2 | YbH2 | LuH2 | |||
Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |
Covalent hydrides | metallic hydrides. |
Ionic hydrides | Intermediate hydrides. |
Do not exist | Not assessed |
Molecular hydrides
Most monomeric hydrides are isolable only under extreme conditions (i.e. at cryogenic temperatures, and often embedded in a rare gas matrix). This is generally attributable to poor contribution of the atomic orbitals of the respective atoms with the s-orbital of hydrogen; and to the low activation enthalpies of autopolymerisation reactions, which electron-deficient monomers are prone to undergo. The table below shows the monomeric hydride for each element, which is closest to, but not surpassing its heuristic valence. A heuristic valence is the valence of an element that strictly obeys the octet, duodectet, and other valence rules. Where available, both the enthalpy of formation for each monomer and the enthalpy of formation for the hydride in its standard state is shown (in brackets) to give a rough indication of which monomers tend to undergo aggregation to lower enthalpic states. For example, monomeric lithium hydride has an enthalpy of formation of 139 kJ mol−1, whereas solid lithium hydride has an enthalpy of −91 kJ mol−1. This means that it is energetically favourable for a mole of monomeric LiH to aggregate into the ionic solid, losing 230 kJ as a consequence. Aggregation can occur as a chemical association, such as polymerisation, or it can occur as an electrostatic association, such as the formation of hydrogen-bonding in water.
Classical hydrides
1 | 2 | 3 | 4 | 5 | 6 | 5 | 4 | 3 | 2 | 1 | 2 | 3 | 4 | 3 | 2 | 1 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
H 2 0 | |||||||||||||||||
LiH[7] 139 (−91) |
BeH 2[8] 123 |
BH 3[9] 107 (41) |
CH 4 −75 |
NH 3 −46 |
H 2O −242 (−286) |
HF −273 | |||||||||||
NaH[10] 140 (−56) |
MgH 2 142 (−76) |
AlH 3[11] 123 (−46) |
SiH 4 34 |
PH 3 5 |
H 2S −21 |
HCl −92 | |||||||||||
KH 132 (−58) |
CaH 2 192 (−174) |
ScH 3 |
TiH 4 |
VH 2[12] |
CrH 2[13] |
MnH 2[14] |
FeH 2[15] 324 |
CoH 2[16] |
NiH 2[17] |
CuH[18] 278 (28) |
ZnH 2[19] 162 |
GaH 3[20] 151 |
GeH 4 92 |
AsH 3 67 |
H 2Se 30 |
HBr −36 | |
RbH 132 (−47) |
SrH 2 201 (−177) |
YH 3 |
ZrH 4 |
NbH 4[12] |
MoH 6[21] |
Tc | RuH 2[15] |
RhH 2[22] |
PdH[23] 361 | AgH[18] 288 | CdH 2[19] 183 |
InH 3[24] 222 |
SnH 4 163 |
SbH 3 146 |
H 2Te 100 |
HI 27 | |
CsH 119 (−50) |
BaH 2 213 (−177) |
HfH 4 |
TaH 4[12] |
WH 6[25] 586 |
ReH 4[14] |
Os | Ir | PtH 2[26] |
AuH[18] 295 | HgH 2[27] 101 |
TlH 3[28] 293 |
PbH 4 252 |
BiH 3 247 |
H 2Po 167 |
HAt 88 | ||
Fr | Ra | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Uut | Fl | Uup | Lv | Uus | ||
↓ | |||||||||||||||||
3 | 4 | 5 | 6 | 7 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 2 | 3 | |||
LaH 3 |
CeH 4 |
PrH 3 |
NdH 4 |
Pm | SmH 4 |
EuH 2[29] |
GdH 3 |
TbH 3 |
DyH 4 |
HoH 3 |
ErH 2 |
TmH | YbH 2 |
LuH 3 | |||
Ac | ThH 4[30] |
Pa | UH 4[31] |
Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |
Monomeric covalent hydride | Oligomeric covalent hydride | ||
Polymeric covalent hydride | Ionic hydride | ||
Unknown solid structure | Not assessed |
This table includes the thermally unstable dihydrogen complexes for the sake of completeness. As with the above table, only the complexes with the most complete valence is shown, to the negligence of the most stable complex.
Non-classical covalent hydrides
8 | 18 | 8 | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
LiH(H 2) 2[7] |
Be | BH 3(H 2) | ||||||||||||
Na | MgH 2(H 2) n[32] |
AlH 3(H 2) | ||||||||||||
K | Ca[33] | ScH 3(H 2) 6[34][35] |
TiH 2(H 2)[36] |
VH 2(H 2)[12] |
CrH2(H2)2 | Mn | FeH 2(H 2) 3[37] |
CoH(H 2) |
Ni(H 2) 4 |
CuH(H2) | ZnH 2(H 2) |
GaH 3(H 2) | ||
Rb | Sr[33] | YH 2(H 2) 3 |
Zr | NbH 4(H 2) 4 |
Mo | Tc | RuH 2(H 2) 4[38] |
RhH3(H2) | Pd(H 2) 3 |
AgH(H2) | CdH(H 2) |
InH 3(H 2)[39] | ||
Cs | Ba[33] | Hf | TaH 4(H 2) 4 |
WH 4(H 2) 4 |
Re | Os | Ir | PtH(H 2) |
AuH 3(H 2) |
Hg | Tl | |||
Fr | Ra | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Uut | |||
↓ | ||||||||||||||
32 | 18 | |||||||||||||
LaH 2(H 2) 2 |
CeH 2(H 2) |
PrH 2(H 2) 2 |
Nd | Pm | Sm | Eu | GdH 2(H 2) |
Tb | Dy | Ho | Er | Tm | Yb | Lu |
Ac | ThH4(H2)4 | Pa | UH 4(H 2) 6[31] |
Np | Pu | Am | Cm | Bk | Cf | Es | Fm | Md | No | Lr |
Assessed | Not assessed |
Hydrogen solutions
Hydrogen has a highly variable solubility in the elements. When the continuous phase of the solution is a metal, it is called a metallic hydride or interstitial hydride, on account of the position of the hydrogen within the crystal structure of the metal. In solution, hydrogen can occur in either the atomic or molecular form. For some elements, when hydrogen content exceeds its solubility, the excess precipitates out as a stoichiometric compound. The table below shows the solubility of hydrogen in each element as a molar ratio at 25 °C (77 °F) and 100 kPa.
He | |||||||||||||||||
LiH <1×10−4 [nb 1][40] |
Be | B | C | N | O | F | Ne | ||||||||||
NaH <8×10−7 [nb 2][41] |
MgH <0.010 [nb 3][42] |
AlH <2.5×10−8 [nb 4][43] |
Si | P | S | Cl | Ar | ||||||||||
KH <<0.01 [nb 5][44] |
CaH <<0.01 [nb 6][45] |
ScH ≥1.86 [nb 7][46] |
TiH 2.00 [nb 8][47] |
VH 1.00 [nb 9][48] |
Cr | MnH <5×10−6 [nb 10][49] |
FeH 3×10−8 [50] |
Co | NiH 3×10−5 [51] |
CuH <1×10−7 [nb 11][52] |
ZnH <3×10−7 [nb 12][53] |
Ga | Ge | As | Se | Br | Kr |
RbH <<0.01 [nb 13][54] |
Sr | YH ≥2.85 [nb 14][55] |
ZrH ≥1.70 [nb 15][56] |
NbH 1.1 [nb 16][57] |
Mo | Tc | Ru | Rh | PdH 0.724 [58] |
AgH 3.84×10−14 [59] |
Cd | In | Sn | Sb | Te | I | Xe |
CsH <<0.01 [nb 17][60] |
Ba | Hf | TaH 0.79 [nb 18][61] |
W | Re | Os | Ir | Pt | AuH 3.06×10−9 [58] |
HgH 5×10−7 [62] |
Tl | Pb | Bi | Po | At | Rn | |
Fr | Ra | Rf | Db | Sg | Bh | Hs | Mt | Ds | Rg | Cn | Uut | Fl | Uup | Lv | Uus | Uuo | |
↓ | |||||||||||||||||
LaH ≥2.03 [nb 19][63] |
CeH ≥2.5 [nb 20][64] |
Pr | Nd | Pm | SmH 3.00 [65] |
Eu | Gd | Tb | Dy | Ho | Er | Tm | Yb | Lu | |||
Ac | Th | Pa | UH ≥3.00 [nb 21][66] |
Np | Pu | Am | Cm | Bk | Cf | Es | FM | Md | No | Lr |
Miscible | Undetermined |
Notes
- ↑ Upper limit imposed by phase diagram, taken at 454 K.
- ↑ Upper limit imposed by phase diagram, taken at 383 K.
- ↑ Upper limit imposed by phase diagram, taken at 650 K and 25 MPa.
- ↑ Upper limit imposed by phase diagram, taken at 556 K.
- ↑ Upper limit imposed by phase diagram.
- ↑ Upper limit imposed by phase diagram, taken at 500 K.
- ↑ Lower limit imposed by phase diagram.
- ↑ Limit imposed by phase diagram.
- ↑ Limit imposed by phase diagram.
- ↑ Upper limit imposed by phase diagram, taken at 500 K.
- ↑ Upper limit imposed by phase diagram, taken at 1000 K.
- ↑ Upper limit at 500 K.
- ↑ Upper limit imposed by phase diagram.
- ↑ Lower limit imposed by phase diagram.
- ↑ Lower limit imposed by phase diagram.
- ↑ Limit imposed by phase diagram.
- ↑ Upper limit imposed by phase diagram.
- ↑ Limit imposed by phase diagram.
- ↑ Lower limit imposed by phase diagram.
- ↑ Lower limit imposed by phase diagram.
- ↑ Lower limit imposed by phase diagram.
References
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- ↑ Main Group Chemistry, 2nd Edition A.G. Massey
- ↑ Advanced Inorganic Chemistry F. Albert Cotton, Geoffrey Wilkinson
- ↑ Inorganic chemistry, Catherine E. Housecroft,A. G. Sharpe
- ↑ Inorganic Chemistry Gary Wulfsberg 2000
- ↑ Data in KJ/mole gas-phase source: Modern Inorganic Chemistry W.L. Jolly
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- 1 2 3 Wang, Xuefeng; Andrews, Lester (December 2004). "Metal Dihydride (MH 2 ) and Dimer (M H2 ) Structures in Solid Argon, Neon, and Hydrogen (M = Ca, Sr, and Ba): Infrared Spectra and Theoretical Calculations". The Journal of Physical Chemistry A 108 (52): 11500–11510. doi:10.1021/jp046046m.
- ↑ Zhao, Yufeng; Kim, Yong-Hyun; Dillon, Anne C.; Heben, Michael J.; Zhang, Shengbai (4 August 2014). "Towards High wt%, Room Temperature Reversible, Carbon-Based Hydrogen Adsorbents". ResearchGate. Retrieved 30 November 2015. Scandium has many empty orbitals to accommodate dihydrogen
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- ↑ Ma, Buyong; Collins, Charlene L.; Schaefer, Henry F. (January 1996). "Periodic Trends for Transition Metal Dihydrides MH , Dihydride Dihydrogen Complexes MH 2 ·H2 , and Tetrahydrides MH4 (M = Ti, V, and Cr)". Journal of the American Chemical Society 118 (4): 870–879. doi:10.1021/ja951376t.
- ↑ Wang, Xuefeng; Andrews, Lester (18 December 2008). "Infrared spectra and theoretical calculations for Fe, Ru, and Os metal hydrides and dihydrogen complexes". The Journal of Physical Chemistry A (American Chemical Society) 113 (3): 551–563. doi:10.1021/jp806845h. Retrieved 24 September 2013.
- ↑ Wang, Xuefeng; Andrews, Lester (13 August 2008). "Infrared spectrum of the RuH
2(H
2)
4 complex in solid hydrogen". Organometallics (American Chemical Society) 27 (17): 4273–4276. doi:10.1021/om800507u. - ↑ Wang, Xuefeng; Andrews, Lester (May 2004). "Infrared Spectra of Indium Hydrides in Solid Hydrogen and Neon". The Journal of Physical Chemistry A 108 (20): 4440–4448. doi:10.1021/jp037942l.
- ↑ Songster, J.; Pélton, A. D. (1 June 1993). "The H-Li (Hydrogen-Lithium) System". Journal of Phase Equilibria (Springer-Verlag) 14 (3): 373–381. doi:10.1007/BF02668238.
- ↑ San-Martin, A.; Manchester, F. D. (1 June 1990). "The H-Na (Hydrogen-Sodium) System". Bulletin of Alloy Phase Diagrams (Springer US) 11 (3): 287–294. doi:10.1007/BF03029300.
- ↑ San-Martin, A.; Manchester, F. D. (1 October 1987). "The H−Mg (Hydrogen-Magnesium) System". Journal of Phase Equilibria (Springer-Verlag) 8 (5): 431–437. doi:10.1007/BF02893152.
- ↑ Qiu, Caian; Olson, Gregory B.; Opalka, Susanne M.; Anton, Donald L. (1 November 2004). "Thermodynamic evaluation of the Al-H system". Journal of Phase Equilibria and Diffusion (Springer-Verlag) 25 (6): 520–527. doi:10.1007/s11669-004-0065-1. ISSN 1863-7345.
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- ↑ Predel, B. (1993). "Ca-H (Calcium-Hydrogen)". In Madelung, O. Ca-Cd – Co-Zr. Springer Berlin Heidelberg. pp. 1–3. ISBN 978-3-540-47411-1.
- ↑ Manchester, F. D.; Pitre, J. M. (1 April 1997). "The H-Sc (Hydrogen-Scandium) System". Journal of Phase Equilibria (Springer-Verlag) 18 (2): 194–205. doi:10.1007/BF02665706.
- ↑ San-Martin, A.; Manchester, F. D. (1 February 1987). "The H−Ti (Hydrogen-Titanium) System". Bulletin of Alloy Phase Diagrams (Springer US) 8 (1): 30–42. doi:10.1007/BF02868888.
- ↑ Predel, B. (1996). "H-V (Hydrogen-Vanadium)". In Madelung, O. Ga-Gd – Hf-Zr. Springer Berlin Heidelberg. pp. 1–5. ISBN 978-3-540-44996-6.
- ↑ San-Martin, A.; Manchester, F. D. (1 June 1995). "The H-Mn (Hydrogen-Manganese) System". Journal of Phase Equilibria (Springer-Verlag) 16 (3): 255–262. doi:10.1007/BF02667311.
- ↑ San-Martin, A.; Manchester, F. D. (1 April 1990). "The Fe-H (Iron-Hydrogen) System". Bulletin of Alloy Phase Diagrams (Springer-Verlag) 11 (2): 173–184. doi:10.1007/BF02841704.
- ↑ Wayman, M. L.; Weatherly, G. C. (1 October 1989). "The H−Ni (Hydrogen-Nickel) System". Bulletin of Alloy Phase Diagrams (Springer US) 10 (5): 569–580. doi:10.1007/BF02882416.
- ↑ Predel, B. (1994). "Cu-H (Copper-Hydrogen)". In Madelung, O. Cr-Cs – Cu-Zr. Springer Berlin Heidelberg. pp. 1–3. ISBN 978-3-540-47417-3.
- ↑ San-Martin, A.; Manchester, F. D. (1 December 1989). "The H-Zn (Hydrogen-Zinc) System". Bulletin of Alloy Phase Diagrams (Springer US) 10 (6): 664–666. doi:10.1007/BF02877640.
- ↑ Sangster, J.; Pelton, A. D. (1 February 1994). "The H-Rb (Hydrogen-Rubidium) System". Journal of Phase Equilibria (Springer-Verlag) 15 (1): 87–89. doi:10.1007/BF02667687.
- ↑ Khatamian, D.; Manchester, F. D. (1 June 1988). "The H−Y (Hydrogen-Yttrium) System". Bulletin of Alloy Phase Diagrams (Springer US) 9 (3): 252–260. doi:10.1007/BF02881276.
- ↑ Zuzek, E.; Abriata, J. P.; San-Martin, A.; Manchester, F. D. (1 August 1990). "The H-Zr (Hydrogen-Zirconium) System". Bulletin of Alloy Phase Diagrams (Springer-Verlag) 11 (4): 385–395. doi:10.1007/BF02843318.
- ↑ Okamoto, H. (1 April 2013). "H-Nb (Hydrogen-Niobium)". Journal of Phase Equilibria and Diffusion (Springer US) 34 (2): 163–164. doi:10.1007/s11669-012-0165-2.
- 1 2 Materials Science International Team (2006). "Au-H-Pd (Gold - Hydrogen - Palladium)". In Effenberg, G.; Ilyenko, S. Noble Metal Systems. Selected Systems from Ag-Al-Zn to Rh-Ru-Sc. Berlin: Springer Berlin Heidelberg. pp. 1–8. ISBN 978-3-540-46994-0.
- ↑ Subramanian, P.R (1 December 1991). "The Ag-H (Silver-Hydrogen) System". Journal of Phase Equilibria (Springer-Verlag) 12 (6): 649–651. doi:10.1007/BF02645164.
- ↑ Songster, J.; Pelton, A. D. (1 February 1994). "The H-Cs (Hydrogen-Cesium) System". Journal of Phase Equilibria (Springer-Verlag) 15 (1): 84–86. doi:10.1007/BF02667686.
- ↑ San-Martin, A.; Manchester, F. D. (1 June 1991). "The H-Ta (Hydrogen-Tantalum) System". Journal of Phase Equilibria (Springer-Verlag) 12 (3): 332–343. doi:10.1007/BF02649922.
- ↑ Guminski, C. (1 October 2002). "The H-Hg (Hydrogen-Mercury) System". Journal of Phase Equilibria (Springer-Verlag) 23 (5): 448–450. doi:10.1361/105497102770331460.
- ↑ Khatamian, D.; Manchester, F. D. (1 February 1990). "The H-La (Hydrogen-Lanthanum) System". Bulletin of Alloy Phase Diagrams (Springer-Verlag) 11 (1): 90–99. doi:10.1007/BF02841589.
- ↑ Manchester, F. D.; Pitre, J. M. (1 February 1997). "The Ce-H (Cerium-Hydrogen) system". Journal of Phase Equilibria (Springer-Verlag) 18 (1): 63–77. doi:10.1007/BF02646759.
- ↑ Zinkevich, M.; Mattern, N.; Handstein, A.; Gutfleisch, O. (13 June 2002). "Thermodynamics of Fe–Sm, Fe–H, and H–Sm Systems and its Application to the Hydrogen–Disproportionation–Desorption–Recombination (HDDR) Process for the System Fe
17Sm
2–H
2". Journal of Alloys and Compounds (Elsevier) 339 (1-2): 118–139. doi:10.1016/S0925-8388(01)01990-9. - ↑ Manchester, F. D.; San-Martin, A. (1 June 1995). "The H-U (Hydrogen-Uranium) System". Journal of Phase Equilibria (Springer-Verlag) 16 (3): 263–275. doi:10.1007/BF02667312.