Editing Hydrogen (section)

===Hydrogen-containing compounds===
{{Main|Hydrogen compounds}}
Hydrogen can exist in both +1 and −1 [[oxidation states]], forming compounds through [[ionic bonding|ionic]] and [[covalent bonding]]. It is a part of a wide range of substances, including water, [[hydrocarbons]], and numerous other [[organic compounds]].<ref name="hydrocarbon">{{cite web| title=Structure and Nomenclature of Hydrocarbons| publisher=Purdue University| url=http://chemed.chem.purdue.edu/genchem/topicreview/bp/1organic/organic.html| access-date=23 March 2008| archive-url=https://web.archive.org/web/20120611084045/http://chemed.chem.purdue.edu/genchem/topicreview/bp/1organic/organic.html| archive-date=11 June 2012}}</ref> The H<sup>+</sup> ion—commonly referred to as a proton due to its single proton and absence of electrons—is central to [[Acid–base reaction|acid–base chemistry]], although the proton does not move freely. In the [[Brønsted–Lowry acids|Brønsted–Lowry]] framework, acids are defined by their ability to donate H<sup>+</sup> ions to bases.<ref>{{Cite book |last=Laurence |first=Christian |title=Lewis basicity and affinity scales: data and measurement |date=2010 |publisher=Wiley |isbn=978-0-470-68189-3 |location=Chichester}}</ref>

Hydrogen forms a vast variety of compounds with [[carbon]] known as hydrocarbons, and an even greater diversity with other elements ([[heteroatoms]]), giving rise to the broad class of organic compounds often associated with living organisms.<ref name="hydrocarbon">{{cite web| title=Structure and Nomenclature of Hydrocarbons| publisher=Purdue University| url=http://chemed.chem.purdue.edu/genchem/topicreview/bp/1organic/organic.html| access-date=23 March 2008| archive-url=https://web.archive.org/web/20120611084045/http://chemed.chem.purdue.edu/genchem/topicreview/bp/1organic/organic.html| archive-date=11 June 2012}}</ref>

[[File:NaH.jpg|thumb|A sample of [[sodium hydride]]]]
Hydrogen compounds with hydrogen in the oxidation state −1 are known as hydrides, which are usually formed between hydrogen and metals. The hydrides can be ionic (aka saline), covalent, nor metallic. With heating, H<sub>2</sub> reacts efficiently with the alkali and alkaline earth metals to give the [[Hydride#Ionic_hydrides|ionic hydrides]] of the formula MH and MH<sub>2</sub>, respectively. These salt-like crystalline compounds have high melting points and all react with water to liberate hydrogen. Covalent hydrides are include [[boranes]] and polymeric [[aluminium hydride]]. [[Transition metals]] form [[metal hydrides]] via continuous dissolution of hydrogen into the metal.<ref name=UllmannH2/> A well known hydride is [[lithium aluminium hydride]], the {{chem2|[AlH4]-}} anion carries hydridic centers firmly attached to the Al(III).<ref>{{Greenwood&Earnshaw2nd|page=228}}</ref>  Perhaps the most extensive series of hydrides are the [[boranes]], compounds consisting only of boron and hydrogen.<ref name="Downs">{{cite journal
|last1=Downs|first1=A. J.
|last2=Pulham|first2=C. R.
|title=The hydrides of aluminium, gallium, indium, and thallium: a re-evaluation
|journal=Chemical Society Reviews
|date=1994|volume=23|pages=175–184
|doi=10.1039/CS9942300175
|issue=3
}}</ref>

Hydrides can bond to these electropositive elements not only as a terminal [[ligand]] but also as [[bridging ligand]]s.  In diborane ({{chem2|B2H6}}), four H's are terminal and two bridge between the two B atoms.<ref name="Miessler" />