Going down the group the number of binary silicon compounds ( silanes) is small (straight or branched but rarely cyclic) for example disilane and trisilane. Not much is known about the final group 13 hydride, thallium hydride.ĭue to the total number of possible binary saturated compounds with carbon of the type C nH 2n+2 being very large, there are many group 14 hydrides. Indium hydride is only stable below −90 ☌ (−130 ☏). In group 13 boron hydrides exist as a highly reactive monomer BH 3, as an adduct for example ammonia borane or as dimeric diborane and as a whole group of BH cluster compounds. In group 12 zinc hydride is a common chemical reagent but cadmium hydride and mercury hydride are very unstable and esoteric. Palladium can absorb up to 900 times its own volume of hydrogen and is therefore actively researched in the field hydrogen storage.Įlements in group 13 to 17 ( p-block) form covalent hydrides (or nonmetal hydrides). Therefore, elements in this block do not form hydrides (the hydride gap) under standard temperature and pressure with the notable exception of palladium. The affinity for hydrogen for most of the d-block elements are low. Bulk actinoid hydrides are only known in this form. 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. It is possible to produce a metallic hydride without requiring decomposition as a necessary step. Both the saline hydrides and the polymeric covalent hydrides typically react strongly with water and air. 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. Such a solid can be thought of as a solid solution and is alternately termed a metallic- or interstitial hydride. The results consist of metallic matrices with dissolved, often stoichiometric or near so, concentrations of hydrogen, ranging from negligible to substantial. Usually, these hydrides rapidly decompose into their component elements at ambient conditions.
However, they usually possess only weak degrees of ionic character. Hydrides in the transition metals and lanthanides are also typically polymeric covalent hydrides. The one exception is beryllium hydride, which has definitively covalent properties. 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. Hydrides in group 2 are polymeric covalent hydrides. Therefore, this category of hydrides contains only a few members. Because hydrogen is located somewhat centrally in an electronegative sense, it is necessary for the counterion to be exceptionally electropositive for the hydride to possibly be accurately described as truly behaving ionic. These hydrogen compounds can be grouped into several types.īinary hydrogen compounds in group 1 are the ionic hydrides (also called saline hydrides) wherein hydrogen is bound electrostatically.
By convention all binary hydrogen compounds are called hydrides even when the hydrogen atom in it is not an anion. Chemical compounds containing only hydrogen and one other chemical elementīinary compounds of hydrogen are binary chemical compounds containing just hydrogen and one other chemical element.
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