Physics:Quantum atoms/hydrogen - Revision history

WikiHarold: Fix final Quantum red link source

2026-05-24T00:07:43Z

Fix final Quantum red link source

← Older revision		Revision as of 00:07, 24 May 2026
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	'''Hydrogen''' is a chemical element; it has the symbol{{nbsp}}'''H''' and atomic number{{nbsp}}1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatomic molecules with the formula{{nbsp}}{{chem2\|H2}}, called '''dihydrogen'''<!--dihydrogen is a redirect to hydrogen; also called '''diprotium'''-->, or sometimes '''hydrogen gas''', '''molecular hydrogen''', or simply hydrogen. Dihydrogen is colorless, odorless, non-toxic, and highly combustible. Stars, including the Sun, mainly consist of hydrogen in a plasma state, while on Earth, hydrogen is found as the gas{{nbsp}}{{chem2\|H2}} (dihydrogen) and in molecules, such as in water and organic compounds. The most common isotope of hydrogen, H, consists of one proton, one electron, and no neutrons.		'''Hydrogen''' is a chemical element; it has the symbol{{nbsp}}'''H''' and atomic number{{nbsp}}1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatomic molecules with the formula{{nbsp}}{{chem2\|H2}}, called '''dihydrogen'''<!--dihydrogen is a redirect to hydrogen; also called '''diprotium'''-->, or sometimes '''hydrogen gas''', '''molecular hydrogen''', or simply hydrogen. Dihydrogen is colorless, odorless, non-toxic, and highly combustible. Stars, including the Sun, mainly consist of hydrogen in a plasma state, while on Earth, hydrogen is found as the gas{{nbsp}}{{chem2\|H2}} (dihydrogen) and in molecules, such as in water and organic compounds. The most common isotope of hydrogen, H, consists of one proton, one electron, and no neutrons.

	Hydrogen gas was first produced artificially in the 17th{{nbsp}}century by the reaction of acids with metals. Henry Cavendish, in{{nbsp}}1766–1781, identified hydrogen gas as a distinct substance and discovered its property of producing water when burned: this is the origin of hydrogen's name, which means (from ~~{{langx\|grc\|ὕδωρ\|~~húdōr\|water}}, and ~~{{langx\|grc\|γεννάω\|~~gennáō\|I bring forth~~\|label=none}}~~). Understanding the colors of light absorbed and emitted by hydrogen was a crucial part of the development of [[Physics:Quantum mechanics\|quantum mechanics]].		Hydrogen gas was first produced artificially in the 17th{{nbsp}}century by the reaction of acids with metals. Henry Cavendish, in{{nbsp}}1766–1781, identified hydrogen gas as a distinct substance and discovered its property of producing water when burned: this is the origin of hydrogen's name, which means (from Ancient Greek ''húdōr'', "water", and ''gennáō'', "I bring forth"). Understanding the colors of light absorbed and emitted by hydrogen was a crucial part of the development of [[Physics:Quantum mechanics\|quantum mechanics]].

	Hydrogen, typically nonmetallic except under extreme pressure, readily forms covalent bonds with most nonmetals, contributing to the formation of compounds like water and various organic substances. Its role is crucial in acid–base reactions, which mainly involve proton exchange among soluble molecules. In ionic compounds, hydrogen can take the form of either a negatively-charged anion, where it is known as hydride, or as a positively charged cation, {{chem2\|H+}}, hydron. Although tightly bonded to water molecules, hydrons strongly affect the behavior of aqueous solutions, as reflected in the importance of pH. Hydride, on the other hand, is rarely observed because it tends to deprotonate solvents, yielding{{nbsp}}{{chem2\|H2}}.<ref>{{Cite web \|title=Element: Hydrogen \|url=https://pse-info.de/en/element/H \|access-date=2026-01-21 \|website=Periodic table \|language=en}}</ref>		Hydrogen, typically nonmetallic except under extreme pressure, readily forms covalent bonds with most nonmetals, contributing to the formation of compounds like water and various organic substances. Its role is crucial in acid–base reactions, which mainly involve proton exchange among soluble molecules. In ionic compounds, hydrogen can take the form of either a negatively-charged anion, where it is known as hydride, or as a positively charged cation, {{chem2\|H+}}, hydron. Although tightly bonded to water molecules, hydrons strongly affect the behavior of aqueous solutions, as reflected in the importance of pH. Hydride, on the other hand, is rarely observed because it tends to deprotonate solvents, yielding{{nbsp}}{{chem2\|H2}}.<ref>{{Cite web \|title=Element: Hydrogen \|url=https://pse-info.de/en/element/H \|access-date=2026-01-21 \|website=Periodic table \|language=en}}</ref>

WikiHarold: Finish Quantum residual red link cleanup

2026-05-23T23:54:21Z

Finish Quantum residual red link cleanup

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2026-05-23T23:46:42Z

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← Older revision		Revision as of 23:46, 23 May 2026
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	==== Isotopes ====		==== Isotopes ====
	~~{{Main\|Physics:Quantum atoms/isotopes of hydrogen}}~~
	[[File:Blausen 0530 HydrogenIsotopes.png\|thumb\|The three naturally-occurring isotopes of hydrogen: hydrogen-1 (protium), hydrogen-2 (deuterium), and hydrogen-3 (tritium)\|alt=Diagram showing the structure of each of Hydrogen-1 (mass number 1, 1 electron, 1 proton), Hydrogen-2 or deuterium (mass number 2, 1 electron, 1 proton, 1 neutron), and Hydrogen-3 or tritium (mass number 3, 1 electron, 1 proton, 2 neutrons)]]		[[File:Blausen 0530 HydrogenIsotopes.png\|thumb\|The three naturally-occurring isotopes of hydrogen: hydrogen-1 (protium), hydrogen-2 (deuterium), and hydrogen-3 (tritium)\|alt=Diagram showing the structure of each of Hydrogen-1 (mass number 1, 1 electron, 1 proton), Hydrogen-2 or deuterium (mass number 2, 1 electron, 1 proton, 1 neutron), and Hydrogen-3 or tritium (mass number 3, 1 electron, 1 proton, 2 neutrons)]]
	Hydrogen has three naturally-occurring isotopes: protium (<math>^1\mathrm{H}</math>), deuterium (<math>^2\mathrm{H}</math> or D), and tritium (<math>^3\mathrm{H}</math> or T). Other highly unstable hydrogen nuclides have been synthesized in laboratories but not observed in nature.<ref name="Gurov">{{cite journal		Hydrogen has three naturally-occurring isotopes: protium (<math>^1\mathrm{H}</math>), deuterium (<math>^2\mathrm{H}</math> or D), and tritium (<math>^3\mathrm{H}</math> or T). Other highly unstable hydrogen nuclides have been synthesized in laboratories but not observed in nature.<ref name="Gurov">{{cite journal
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	==== Spin isomers ====		==== Spin isomers ====
	~~{{Main\|Physics:Quantum atoms/spin isomers of hydrogen}}~~
	Molecular {{chem2\|H2}} exists as two nuclear isomers that differ in the spin states of their nuclei.<ref name="uigi">{{cite web\|author=Staff\|date=2003\|url=http://www.uigi.com/hydrogen.html\|title=Hydrogen (H<sub>2</sub>) Properties, Uses, Applications: Hydrogen Gas and Liquid Hydrogen\|publisher=Universal Industrial Gases, Inc.\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080219073329/http://www.uigi.com/hydrogen.html\|archive-date=19 February 2008\|url-status=live}}</ref> In the '''''' form, the spins of the two nuclei are parallel, forming a spin triplet state having a total molecular spin <math>S = 1</math>; in the '''''' form the spins are and form a spin singlet state having spin <math>S = 0</math>. The equilibrium ratio of ortho- to para-hydrogen depends on temperature. At room temperature or warmer, equilibrium hydrogen gas contains about 25% of the para form and 75% of the ortho form.<ref name="Green2012">{{cite journal \|last1=Green \|first1=Richard A. \|display-authors=0 \|title=The theory and practice of hyperpolarization in magnetic resonance using ''para''hydrogen \|journal=Prog. Nucl. Magn. Reson. Spectrosc. \|date=2012 \|volume=67 \|pages=1–48 \|doi=10.1016/j.pnmrs.2012.03.001 \|pmid=23101588 \|bibcode=2012PNMRS..67....1G \|url=https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|access-date=28 August 2021 \|archive-date=28 August 2021 \|archive-url=https://web.archive.org/web/20210828222611/https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|url-status=live \|url-access=subscription }}</ref> The ortho form is an excited state, having higher energy than the para form by {{val\|1.455\|ul=kJ/mol}},<ref name="PlanckInstitut">{{cite web \|url=https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|language=de \|website=Max-Planck-Institut für Biophysikalische Chemie \|title=Die Entdeckung des para-Wasserstoffs (The discovery of para-hydrogen) \|access-date=9 November 2020 \|archive-date=16 November 2020 \|archive-url=https://web.archive.org/web/20201116064055/https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|url-status=live }}</ref> and it converts to the para form over the course of several minutes when cooled to low temperature.<ref>{{cite journal\|last1=Milenko\|first1=Yu. Ya.\|last2=Sibileva\|first2=R. M.\|last3=Strzhemechny\|first3=M. A.\|title=Natural ortho-para conversion rate in liquid and gaseous hydrogen\|journal=Journal of Low Temperature Physics\|date=1997\|volume=107\|issue=1–2\|pages=77–92		Molecular {{chem2\|H2}} exists as two nuclear isomers that differ in the spin states of their nuclei.<ref name="uigi">{{cite web\|author=Staff\|date=2003\|url=http://www.uigi.com/hydrogen.html\|title=Hydrogen (H<sub>2</sub>) Properties, Uses, Applications: Hydrogen Gas and Liquid Hydrogen\|publisher=Universal Industrial Gases, Inc.\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080219073329/http://www.uigi.com/hydrogen.html\|archive-date=19 February 2008\|url-status=live}}</ref> In the '''''' form, the spins of the two nuclei are parallel, forming a spin triplet state having a total molecular spin <math>S = 1</math>; in the '''''' form the spins are and form a spin singlet state having spin <math>S = 0</math>. The equilibrium ratio of ortho- to para-hydrogen depends on temperature. At room temperature or warmer, equilibrium hydrogen gas contains about 25% of the para form and 75% of the ortho form.<ref name="Green2012">{{cite journal \|last1=Green \|first1=Richard A. \|display-authors=0 \|title=The theory and practice of hyperpolarization in magnetic resonance using ''para''hydrogen \|journal=Prog. Nucl. Magn. Reson. Spectrosc. \|date=2012 \|volume=67 \|pages=1–48 \|doi=10.1016/j.pnmrs.2012.03.001 \|pmid=23101588 \|bibcode=2012PNMRS..67....1G \|url=https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|access-date=28 August 2021 \|archive-date=28 August 2021 \|archive-url=https://web.archive.org/web/20210828222611/https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|url-status=live \|url-access=subscription }}</ref> The ortho form is an excited state, having higher energy than the para form by {{val\|1.455\|ul=kJ/mol}},<ref name="PlanckInstitut">{{cite web \|url=https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|language=de \|website=Max-Planck-Institut für Biophysikalische Chemie \|title=Die Entdeckung des para-Wasserstoffs (The discovery of para-hydrogen) \|access-date=9 November 2020 \|archive-date=16 November 2020 \|archive-url=https://web.archive.org/web/20201116064055/https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|url-status=live }}</ref> and it converts to the para form over the course of several minutes when cooled to low temperature.<ref>{{cite journal\|last1=Milenko\|first1=Yu. Ya.\|last2=Sibileva\|first2=R. M.\|last3=Strzhemechny\|first3=M. A.\|title=Natural ortho-para conversion rate in liquid and gaseous hydrogen\|journal=Journal of Low Temperature Physics\|date=1997\|volume=107\|issue=1–2\|pages=77–92
	\|doi=10.1007/BF02396837\|bibcode = 1997JLTP..107...77M \|s2cid=120832814}}</ref> The thermal properties of these isomers differ because each has distinct rotational quantum states.<!-- This link is less direct than Rotational spectroscopy but presently the subject better (June 2021).--><ref name="NASA">{{cite web\|last=Hritz\|first=J.\|date=March 2006\|url=http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|title=CH. 6 – Hydrogen\|work=NASA Glenn Research Center Glenn Safety Manual, Document GRC-MQSA.001\|publisher=NASA\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080216050326/http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|archive-date=16 February 2008}}</ref>		\|doi=10.1007/BF02396837\|bibcode = 1997JLTP..107...77M \|s2cid=120832814}}</ref> The thermal properties of these isomers differ because each has distinct rotational quantum states.<!-- This link is less direct than Rotational spectroscopy but presently the subject better (June 2021).--><ref name="NASA">{{cite web\|last=Hritz\|first=J.\|date=March 2006\|url=http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|title=CH. 6 – Hydrogen\|work=NASA Glenn Research Center Glenn Safety Manual, Document GRC-MQSA.001\|publisher=NASA\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080216050326/http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|archive-date=16 February 2008}}</ref>
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	== History ==		== History ==
	~~{{Main\|Physics:Timeline of hydrogen technologies}}~~

	=== 18th century ===		=== 18th century ===
	[[File:Portret van Robert Boyle, RP-P-OB-4578 (cropped).jpg\|thumb\|Robert Boyle, who discovered the reaction between iron filings and dilute acids]]		[[File:Portret van Robert Boyle, RP-P-OB-4578 (cropped).jpg\|thumb\|Robert Boyle, who discovered the reaction between iron filings and dilute acids]]
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	===Hydrogen-containing compounds===		===Hydrogen-containing compounds===
	~~{{Main\|Chemistry:Hydrogen compounds}}~~
	Hydrogen can exist in both +1 and −1{{nbsp}}oxidation states, forming compounds through ionic and covalent bonding. The element is 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=https://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>{{nbsp}}ion—commonly referred to as a proton due to its single proton and absence of electrons—is central to acid–base chemistry, although the proton does not move freely. In the –Lowry framework, acids are defined by their ability to donate H<sup>+</sup>{{nbsp}}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 can exist in both +1 and −1{{nbsp}}oxidation states, forming compounds through ionic and covalent bonding. The element is 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=https://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>{{nbsp}}ion—commonly referred to as a proton due to its single proton and absence of electrons—is central to acid–base chemistry, although the proton does not move freely. In the –Lowry framework, acids are defined by their ability to donate H<sup>+</sup>{{nbsp}}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>

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	=== Hydrogen bonding ===		=== Hydrogen bonding ===
	~~{{Main\|Chemistry:Hydrogen bond}}~~
	When bonded to a more electronegative element, particularly fluorine, oxygen, or nitrogen, hydrogen can participate in a form of medium-strength noncovalent bonding with another electronegative element with a lone pair like oxygen or nitrogen. This phenomenon, called hydrogen bonding, is critical to the stability of many biological molecules.<ref>{{Cite journal \|last1=Pimentel \|first1=G C \|last2=McClellan \|first2=A L \|date=October 1971 \|title=Hydrogen Bonding \|url=https://www.annualreviews.org/doi/10.1146/annurev.pc.22.100171.002023 \|journal=Annual Review of Physical Chemistry \|language=en \|volume=22 \|issue=1 \|pages=347–385 \|doi=10.1146/annurev.pc.22.100171.002023 \|bibcode=1971ARPC...22..347P \|issn=0066-426X\|url-access=subscription }}</ref>{{rp\|375}}<ref>IUPAC Compendium of Chemical Terminology, Electronic version, [http://goldbook.iupac.org/H02899.html Hydrogen Bond] {{Webarchive\|url=https://web.archive.org/web/20080319045705/http://goldbook.iupac.org/H02899.html \|date=19 March 2008 }}</ref> Hydrogen bonding alters molecule structures, viscosity, solubility, melting and boiling points, and even protein folding dynamics.<ref>{{Cite journal \|last1=Xie \|first1=Zhenkai \|last2=Luo \|first2=Rui \|last3=Ying \|first3=Tianping \|last4=Gao \|first4=Yurui \|last5=Song \|first5=Boqin \|last6=Yu \|first6=Tongxu \|last7=Chen \|first7=Xu \|last8=Hao \|first8=Munan \|last9=Chai \|first9=Congcong \|last10=Yan \|first10=Jiashu \|last11=Huang \|first11=Zhiheng \|last12=Chen \|first12=Zhiguo \|last13=Du \|first13=Luojun \|last14=Zhu \|first14=Chongqin \|last15=Guo \|first15=Jiangang \|date=November 2024 \|title=Dynamic-to-static switch of hydrogen bonds induces a metal–insulator transition in an organic–inorganic superlattice \|url=https://www.nature.com/articles/s41557-024-01566-1 \|journal=Nature Chemistry \|language=en \|volume=16 \|issue=11 \|pages=1803–1810 \|doi=10.1038/s41557-024-01566-1 \|pmid=39143300 \|bibcode=2024NatCh..16.1803X \|issn=1755-4330\|url-access=subscription }}</ref>		When bonded to a more electronegative element, particularly fluorine, oxygen, or nitrogen, hydrogen can participate in a form of medium-strength noncovalent bonding with another electronegative element with a lone pair like oxygen or nitrogen. This phenomenon, called hydrogen bonding, is critical to the stability of many biological molecules.<ref>{{Cite journal \|last1=Pimentel \|first1=G C \|last2=McClellan \|first2=A L \|date=October 1971 \|title=Hydrogen Bonding \|url=https://www.annualreviews.org/doi/10.1146/annurev.pc.22.100171.002023 \|journal=Annual Review of Physical Chemistry \|language=en \|volume=22 \|issue=1 \|pages=347–385 \|doi=10.1146/annurev.pc.22.100171.002023 \|bibcode=1971ARPC...22..347P \|issn=0066-426X\|url-access=subscription }}</ref>{{rp\|375}}<ref>IUPAC Compendium of Chemical Terminology, Electronic version, [http://goldbook.iupac.org/H02899.html Hydrogen Bond] {{Webarchive\|url=https://web.archive.org/web/20080319045705/http://goldbook.iupac.org/H02899.html \|date=19 March 2008 }}</ref> Hydrogen bonding alters molecule structures, viscosity, solubility, melting and boiling points, and even protein folding dynamics.<ref>{{Cite journal \|last1=Xie \|first1=Zhenkai \|last2=Luo \|first2=Rui \|last3=Ying \|first3=Tianping \|last4=Gao \|first4=Yurui \|last5=Song \|first5=Boqin \|last6=Yu \|first6=Tongxu \|last7=Chen \|first7=Xu \|last8=Hao \|first8=Munan \|last9=Chai \|first9=Congcong \|last10=Yan \|first10=Jiashu \|last11=Huang \|first11=Zhiheng \|last12=Chen \|first12=Zhiguo \|last13=Du \|first13=Luojun \|last14=Zhu \|first14=Chongqin \|last15=Guo \|first15=Jiangang \|date=November 2024 \|title=Dynamic-to-static switch of hydrogen bonds induces a metal–insulator transition in an organic–inorganic superlattice \|url=https://www.nature.com/articles/s41557-024-01566-1 \|journal=Nature Chemistry \|language=en \|volume=16 \|issue=11 \|pages=1803–1810 \|doi=10.1038/s41557-024-01566-1 \|pmid=39143300 \|bibcode=2024NatCh..16.1803X \|issn=1755-4330\|url-access=subscription }}</ref>

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	== Production and storage==		== Production and storage==
	~~{{Main\|Chemistry:Hydrogen production}}~~

	===Industrial routes===		===Industrial routes===
	Nearly all of the world's current supply of hydrogen gas{{nbsp}}({{chem2\|H2}}) is produced from fossil fuels,<ref>{{cite news \|last1=Reed \|first1=Stanley \|last2=Ewing \|first2=Jack \|date=13 July 2021 \|title=Hydrogen Is One Answer to Climate Change. Getting It Is the Hard Part \|url=https://www.nytimes.com/2021/07/13/business/hydrogen-climate-change.html \|work=The New York Times}}</ref><ref name="rosenow-2022">{{cite journal \|last1=Rosenow \|first1=Jan \|date=27 September 2022 \|title=Is heating homes with hydrogen all but a pipe dream? An evidence review \|journal=Joule \|volume=6 \|issue=10 \|pages=2225–2228 \|bibcode=2022Joule...6.2225R \|doi=10.1016/j.joule.2022.08.015 \|s2cid=252584593 \|doi-access=free}} Article in press.</ref>{{rp\|1}} with less than 1% of hydrogen being produced by low-emissions technologies in 2025.<ref>{{cite web\|url=https://www.iea.org/reports/global-hydrogen-review-2025/production-highlights-2\|title=Production highlights - Global Hydrogen Review 2025\|website=IEA}}</ref> Many methods exist for producing H<sub>2</sub>, but three dominate commercially: steam reforming often coupled to water-gas shift, partial oxidation of hydrocarbons, and water electrolysis.<ref name=KO/>		Nearly all of the world's current supply of hydrogen gas{{nbsp}}({{chem2\|H2}}) is produced from fossil fuels,<ref>{{cite news \|last1=Reed \|first1=Stanley \|last2=Ewing \|first2=Jack \|date=13 July 2021 \|title=Hydrogen Is One Answer to Climate Change. Getting It Is the Hard Part \|url=https://www.nytimes.com/2021/07/13/business/hydrogen-climate-change.html \|work=The New York Times}}</ref><ref name="rosenow-2022">{{cite journal \|last1=Rosenow \|first1=Jan \|date=27 September 2022 \|title=Is heating homes with hydrogen all but a pipe dream? An evidence review \|journal=Joule \|volume=6 \|issue=10 \|pages=2225–2228 \|bibcode=2022Joule...6.2225R \|doi=10.1016/j.joule.2022.08.015 \|s2cid=252584593 \|doi-access=free}} Article in press.</ref>{{rp\|1}} with less than 1% of hydrogen being produced by low-emissions technologies in 2025.<ref>{{cite web\|url=https://www.iea.org/reports/global-hydrogen-review-2025/production-highlights-2\|title=Production highlights - Global Hydrogen Review 2025\|website=IEA}}</ref> Many methods exist for producing H<sub>2</sub>, but three dominate commercially: steam reforming often coupled to water-gas shift, partial oxidation of hydrocarbons, and water electrolysis.<ref name=KO/>
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	== Applications ==		== Applications ==
	~~{{See also\|Physics:Hydrogen economy}}~~
	[[File:2023-10-19 Clean Hydrogen Ladder 5.0.png\|thumb\|upright=2\|Hydrogen Ladder: Ranking of hydrogen applications and uses in the medium term, but analysts disagree<ref>{{Cite web \|last=Barnard \|first=Michael \|date=2023-10-22 \|title=What's New On The Rungs Of Liebreich's Hydrogen Ladder? \|url=https://cleantechnica.com/2023/10/22/whats-new-on-the-rungs-of-liebreichs-hydrogen-ladder/ \|access-date=2024-03-10 \|website=CleanTechnica \|language=en-US}}</ref>]]		[[File:2023-10-19 Clean Hydrogen Ladder 5.0.png\|thumb\|upright=2\|Hydrogen Ladder: Ranking of hydrogen applications and uses in the medium term, but analysts disagree<ref>{{Cite web \|last=Barnard \|first=Michael \|date=2023-10-22 \|title=What's New On The Rungs Of Liebreich's Hydrogen Ladder? \|url=https://cleantechnica.com/2023/10/22/whats-new-on-the-rungs-of-liebreichs-hydrogen-ladder/ \|access-date=2024-03-10 \|website=CleanTechnica \|language=en-US}}</ref>]]

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	== Safety and precautions ==		== Safety and precautions ==
	~~{{Main\|Chemistry:Hydrogen safety}}~~
	{{Chembox		{{Chembox
	\| container_only = yes		\| container_only = yes
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	{{Periodic table (navbox)}}		{{Periodic table (navbox)}}

	~~[[Category:Hydrogen\| ]]~~
	~~[[Category:Chemical elements]]~~
	~~[[Category:Reactive nonmetals]]~~
	~~[[Category:Diatomic nonmetals]]~~
	~~[[Category:Nuclear fusion fuels]]~~
	~~[[Category:Airship technology]]~~
	~~[[Category:Reducing agents]]~~
	~~[[Category:Refrigerants]]~~
	~~[[Category:Gaseous signaling molecules]]~~
	~~[[Category:E-number additives]]~~
	{{Author\|Harold Foppele}}		{{Author\|Harold Foppele}}
	{{Sourceattribution\|Physics:Quantum atoms/hydrogen\|1}}		{{Sourceattribution\|Physics:Quantum atoms/hydrogen\|1}}

WikiHarold: Clean Quantum page image and red links

2026-05-23T23:33:31Z

Clean Quantum page image and red links

← Older revision		Revision as of 23:33, 23 May 2026
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	Nearly all hydrogen production is done by transforming fossil fuels, particularly steam reforming of natural gas. It can also be produced from water or saline by electrolysis, but this process is more expensive. Its main industrial uses include fossil fuel processing and ammonia production for fertilizer. Emerging uses for hydrogen include the use of fuel cells to generate electricity.		Nearly all hydrogen production is done by transforming fossil fuels, particularly steam reforming of natural gas. It can also be produced from water or saline by electrolysis, but this process is more expensive. Its main industrial uses include fossil fuel processing and ammonia production for fertilizer. Emerging uses for hydrogen include the use of fuel cells to generate electricity.


	</div>		</div>
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	* [http://militzer.berkeley.edu/diss/node5.html High temperature hydrogen phase diagram] from Burkhard Militzer (University of California, Berkeley)		* [http://militzer.berkeley.edu/diss/node5.html High temperature hydrogen phase diagram] from Burkhard Militzer (University of California, Berkeley)
	* [http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/hydwf.html#c3 Wavefunction of hydrogen] at ''HyperPhysics'' (Georgia State University)		* [http://hyperphysics.phy-astr.gsu.edu/Hbase/quantum/hydwf.html#c3 Wavefunction of hydrogen] at ''HyperPhysics'' (Georgia State University)


	{{Periodic table (navbox)}}		{{Periodic table (navbox)}}



	[[Category:Hydrogen\| ]]		[[Category:Hydrogen\| ]]

Maintenance script: Point hydrogen spin-isomer links to Quantum Collection title

2026-05-23T10:39:14Z

Point hydrogen spin-isomer links to Quantum Collection title

← Older revision		Revision as of 10:39, 23 May 2026
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	==== Spin isomers ====		==== Spin isomers ====
	{{Main\|Physics:~~Spin~~ isomers of hydrogen}}		{{Main\|Physics:Quantum atoms/spin isomers of hydrogen}}
	Molecular {{chem2\|H2}} exists as two nuclear isomers that differ in the spin states of their nuclei.<ref name="uigi">{{cite web\|author=Staff\|date=2003\|url=http://www.uigi.com/hydrogen.html\|title=Hydrogen (H<sub>2</sub>) Properties, Uses, Applications: Hydrogen Gas and Liquid Hydrogen\|publisher=Universal Industrial Gases, Inc.\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080219073329/http://www.uigi.com/hydrogen.html\|archive-date=19 February 2008\|url-status=live}}</ref> In the '''''' form, the spins of the two nuclei are parallel, forming a spin triplet state having a total molecular spin <math>S = 1</math>; in the '''''' form the spins are and form a spin singlet state having spin <math>S = 0</math>. The equilibrium ratio of ortho- to para-hydrogen depends on temperature. At room temperature or warmer, equilibrium hydrogen gas contains about 25% of the para form and 75% of the ortho form.<ref name="Green2012">{{cite journal \|last1=Green \|first1=Richard A. \|display-authors=0 \|title=The theory and practice of hyperpolarization in magnetic resonance using ''para''hydrogen \|journal=Prog. Nucl. Magn. Reson. Spectrosc. \|date=2012 \|volume=67 \|pages=1–48 \|doi=10.1016/j.pnmrs.2012.03.001 \|pmid=23101588 \|bibcode=2012PNMRS..67....1G \|url=https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|access-date=28 August 2021 \|archive-date=28 August 2021 \|archive-url=https://web.archive.org/web/20210828222611/https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|url-status=live \|url-access=subscription }}</ref> The ortho form is an excited state, having higher energy than the para form by {{val\|1.455\|ul=kJ/mol}},<ref name="PlanckInstitut">{{cite web \|url=https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|language=de \|website=Max-Planck-Institut für Biophysikalische Chemie \|title=Die Entdeckung des para-Wasserstoffs (The discovery of para-hydrogen) \|access-date=9 November 2020 \|archive-date=16 November 2020 \|archive-url=https://web.archive.org/web/20201116064055/https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|url-status=live }}</ref> and it converts to the para form over the course of several minutes when cooled to low temperature.<ref>{{cite journal\|last1=Milenko\|first1=Yu. Ya.\|last2=Sibileva\|first2=R. M.\|last3=Strzhemechny\|first3=M. A.\|title=Natural ortho-para conversion rate in liquid and gaseous hydrogen\|journal=Journal of Low Temperature Physics\|date=1997\|volume=107\|issue=1–2\|pages=77–92		Molecular {{chem2\|H2}} exists as two nuclear isomers that differ in the spin states of their nuclei.<ref name="uigi">{{cite web\|author=Staff\|date=2003\|url=http://www.uigi.com/hydrogen.html\|title=Hydrogen (H<sub>2</sub>) Properties, Uses, Applications: Hydrogen Gas and Liquid Hydrogen\|publisher=Universal Industrial Gases, Inc.\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080219073329/http://www.uigi.com/hydrogen.html\|archive-date=19 February 2008\|url-status=live}}</ref> In the '''''' form, the spins of the two nuclei are parallel, forming a spin triplet state having a total molecular spin <math>S = 1</math>; in the '''''' form the spins are and form a spin singlet state having spin <math>S = 0</math>. The equilibrium ratio of ortho- to para-hydrogen depends on temperature. At room temperature or warmer, equilibrium hydrogen gas contains about 25% of the para form and 75% of the ortho form.<ref name="Green2012">{{cite journal \|last1=Green \|first1=Richard A. \|display-authors=0 \|title=The theory and practice of hyperpolarization in magnetic resonance using ''para''hydrogen \|journal=Prog. Nucl. Magn. Reson. Spectrosc. \|date=2012 \|volume=67 \|pages=1–48 \|doi=10.1016/j.pnmrs.2012.03.001 \|pmid=23101588 \|bibcode=2012PNMRS..67....1G \|url=https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|access-date=28 August 2021 \|archive-date=28 August 2021 \|archive-url=https://web.archive.org/web/20210828222611/https://www.sciencedirect.com/science/article/abs/pii/S0079656512000477 \|url-status=live \|url-access=subscription }}</ref> The ortho form is an excited state, having higher energy than the para form by {{val\|1.455\|ul=kJ/mol}},<ref name="PlanckInstitut">{{cite web \|url=https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|language=de \|website=Max-Planck-Institut für Biophysikalische Chemie \|title=Die Entdeckung des para-Wasserstoffs (The discovery of para-hydrogen) \|access-date=9 November 2020 \|archive-date=16 November 2020 \|archive-url=https://web.archive.org/web/20201116064055/https://www.mpibpc.mpg.de/146336/para-Wasserstoff \|url-status=live }}</ref> and it converts to the para form over the course of several minutes when cooled to low temperature.<ref>{{cite journal\|last1=Milenko\|first1=Yu. Ya.\|last2=Sibileva\|first2=R. M.\|last3=Strzhemechny\|first3=M. A.\|title=Natural ortho-para conversion rate in liquid and gaseous hydrogen\|journal=Journal of Low Temperature Physics\|date=1997\|volume=107\|issue=1–2\|pages=77–92
	\|doi=10.1007/BF02396837\|bibcode = 1997JLTP..107...77M \|s2cid=120832814}}</ref> The thermal properties of these isomers differ because each has distinct rotational quantum states.<!-- This link is less direct than Rotational spectroscopy but presently the subject better (June 2021).--><ref name="NASA">{{cite web\|last=Hritz\|first=J.\|date=March 2006\|url=http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|title=CH. 6 – Hydrogen\|work=NASA Glenn Research Center Glenn Safety Manual, Document GRC-MQSA.001\|publisher=NASA\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080216050326/http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|archive-date=16 February 2008}}</ref>		\|doi=10.1007/BF02396837\|bibcode = 1997JLTP..107...77M \|s2cid=120832814}}</ref> The thermal properties of these isomers differ because each has distinct rotational quantum states.<!-- This link is less direct than Rotational spectroscopy but presently the subject better (June 2021).--><ref name="NASA">{{cite web\|last=Hritz\|first=J.\|date=March 2006\|url=http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|title=CH. 6 – Hydrogen\|work=NASA Glenn Research Center Glenn Safety Manual, Document GRC-MQSA.001\|publisher=NASA\|access-date=5 February 2008\|archive-url=https://web.archive.org/web/20080216050326/http://smad-ext.grc.nasa.gov/gso/manual/chapter_06.pdf\|archive-date=16 February 2008}}</ref>

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	==== Isotopes ====		==== Isotopes ====
	{{Main\|Physics:~~Isotopes~~ of hydrogen}}		{{Main\|Physics:Quantum atoms/isotopes of hydrogen}}
	[[File:Blausen 0530 HydrogenIsotopes.png\|thumb\|The three naturally-occurring isotopes of hydrogen: hydrogen-1 (protium), hydrogen-2 (deuterium), and hydrogen-3 (tritium)\|alt=Diagram showing the structure of each of Hydrogen-1 (mass number 1, 1 electron, 1 proton), Hydrogen-2 or deuterium (mass number 2, 1 electron, 1 proton, 1 neutron), and Hydrogen-3 or tritium (mass number 3, 1 electron, 1 proton, 2 neutrons)]]		[[File:Blausen 0530 HydrogenIsotopes.png\|thumb\|The three naturally-occurring isotopes of hydrogen: hydrogen-1 (protium), hydrogen-2 (deuterium), and hydrogen-3 (tritium)\|alt=Diagram showing the structure of each of Hydrogen-1 (mass number 1, 1 electron, 1 proton), Hydrogen-2 or deuterium (mass number 2, 1 electron, 1 proton, 1 neutron), and Hydrogen-3 or tritium (mass number 3, 1 electron, 1 proton, 2 neutrons)]]
	Hydrogen has three naturally-occurring isotopes: protium (<math>^1\mathrm{H}</math>), deuterium (<math>^2\mathrm{H}</math> or D), and tritium (<math>^3\mathrm{H}</math> or T). Other highly unstable hydrogen nuclides have been synthesized in laboratories but not observed in nature.<ref name="Gurov">{{cite journal		Hydrogen has three naturally-occurring isotopes: protium (<math>^1\mathrm{H}</math>), deuterium (<math>^2\mathrm{H}</math> or D), and tritium (<math>^3\mathrm{H}</math> or T). Other highly unstable hydrogen nuclides have been synthesized in laboratories but not observed in nature.<ref name="Gurov">{{cite journal

Harold: /* Electron energy levels */

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Electron energy levels

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	===Atomic hydrogen===		===Atomic hydrogen===
	==== Electron energy levels ====		==== Electron energy levels ====
	~~{{Main\|Physics:Hydrogen atom}}~~
	The ground state energy level of the electron in a hydrogen atom is −13.6{{nbsp}}electronvolts{{nbsp}}(eV),<ref>{{cite web\|author1=NAAP Labs\|title=Energy Levels\|url=http://astro.unl.edu/naap/hydrogen/levels.html\|publisher=University of Nebraska Lincoln\|access-date=20 May 2015\|date=2009\|archive-url=https://web.archive.org/web/20150511120536/http://astro.unl.edu/naap/hydrogen/levels.html\|archive-date=11 May 2015\|url-status=live}}</ref> equivalent to an ultraviolet photon of roughly 91{{nbsp}}nanometers wavelength.<ref>{{cite web\|url=http://www.wolframalpha.com/input/?i=photon+wavelength+13.6+ev\|title=photon wavelength 13.6 eV\|access-date=20 May 2015\|date=20 May 2015\|work=Wolfram Alpha\|archive-url=https://web.archive.org/web/20160512221720/http://www.wolframalpha.com/input/?i=photon+wavelength+13.6+ev\|archive-date=12 May 2016\|url-status=live}}</ref> The energy levels of hydrogen are referred to by consecutive [[Physics:Quantum number\|quantum number]]s, with <math>n=1</math> being the ground state. The hydrogen spectral series corresponds to emission of light due to transitions from higher to lower energy levels.<ref>{{Cite book \|last=Levine \|first=Ira N. \|title=Quantum chemistry \|date=1970 \|publisher=Pearson \|isbn=978-0-321-89060-3 \|edition=2 \|series=Pearson advanced chemistry series \|location=Boston}}</ref>{{rp\|105}} Each energy level is further split by spin interactions between the electron and proton into four hyperfine levels.<ref>{{Cite book \|last1=Feynman \|first1=Richard P. \|title=The Feynman lectures on physics \|last2=Leighton \|first2=Robert B. \|last3=Sands \|first3=Matthew L. \|date=2011 \|publisher=Basic Books \|isbn=978-0-465-02414-8 \|edition=New millennium \|location=New York \|chapter=The Hyperfine Splitting in Hydrogen \|oclc=671704374 \|chapter-url=https://www.feynmanlectures.caltech.edu/III_12.html}}</ref>		The ground state energy level of the electron in a hydrogen atom is −13.6{{nbsp}}electronvolts{{nbsp}}(eV),<ref>{{cite web\|author1=NAAP Labs\|title=Energy Levels\|url=http://astro.unl.edu/naap/hydrogen/levels.html\|publisher=University of Nebraska Lincoln\|access-date=20 May 2015\|date=2009\|archive-url=https://web.archive.org/web/20150511120536/http://astro.unl.edu/naap/hydrogen/levels.html\|archive-date=11 May 2015\|url-status=live}}</ref> equivalent to an ultraviolet photon of roughly 91{{nbsp}}nanometers wavelength.<ref>{{cite web\|url=http://www.wolframalpha.com/input/?i=photon+wavelength+13.6+ev\|title=photon wavelength 13.6 eV\|access-date=20 May 2015\|date=20 May 2015\|work=Wolfram Alpha\|archive-url=https://web.archive.org/web/20160512221720/http://www.wolframalpha.com/input/?i=photon+wavelength+13.6+ev\|archive-date=12 May 2016\|url-status=live}}</ref> The energy levels of hydrogen are referred to by consecutive [[Physics:Quantum number\|quantum number]]s, with <math>n=1</math> being the ground state. The hydrogen spectral series corresponds to emission of light due to transitions from higher to lower energy levels.<ref>{{Cite book \|last=Levine \|first=Ira N. \|title=Quantum chemistry \|date=1970 \|publisher=Pearson \|isbn=978-0-321-89060-3 \|edition=2 \|series=Pearson advanced chemistry series \|location=Boston}}</ref>{{rp\|105}} Each energy level is further split by spin interactions between the electron and proton into four hyperfine levels.<ref>{{Cite book \|last1=Feynman \|first1=Richard P. \|title=The Feynman lectures on physics \|last2=Leighton \|first2=Robert B. \|last3=Sands \|first3=Matthew L. \|date=2011 \|publisher=Basic Books \|isbn=978-0-465-02414-8 \|edition=New millennium \|location=New York \|chapter=The Hyperfine Splitting in Hydrogen \|oclc=671704374 \|chapter-url=https://www.feynmanlectures.caltech.edu/III_12.html}}</ref>

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	== History ==		== History ==
			{{Main\|Physics:Timeline of hydrogen technologies}}

	=== 18th century ===		=== 18th century ===
	[[File:Portret van Robert Boyle, RP-P-OB-4578 (cropped).jpg\|thumb\|Robert Boyle, who discovered the reaction between iron filings and dilute acids]]		[[File:Portret van Robert Boyle, RP-P-OB-4578 (cropped).jpg\|thumb\|Robert Boyle, who discovered the reaction between iron filings and dilute acids]]

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	== History ==		== History ==
	~~{{Main\|Physics:Timeline of hydrogen technologies}}~~

	=== 18th century ===		=== 18th century ===
	[[File:Portret van Robert Boyle, RP-P-OB-4578 (cropped).jpg\|thumb\|Robert Boyle, who discovered the reaction between iron filings and dilute acids]]		[[File:Portret van Robert Boyle, RP-P-OB-4578 (cropped).jpg\|thumb\|Robert Boyle, who discovered the reaction between iron filings and dilute acids]]

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	{{Main\|Physics:Isotopes of hydrogen}}		{{Main\|Physics:Isotopes of hydrogen}}
	[[File:Blausen 0530 HydrogenIsotopes.png\|thumb\|The three naturally-occurring isotopes of hydrogen: hydrogen-1 (protium), hydrogen-2 (deuterium), and hydrogen-3 (tritium)\|alt=Diagram showing the structure of each of Hydrogen-1 (mass number 1, 1 electron, 1 proton), Hydrogen-2 or deuterium (mass number 2, 1 electron, 1 proton, 1 neutron), and Hydrogen-3 or tritium (mass number 3, 1 electron, 1 proton, 2 neutrons)]]		[[File:Blausen 0530 HydrogenIsotopes.png\|thumb\|The three naturally-occurring isotopes of hydrogen: hydrogen-1 (protium), hydrogen-2 (deuterium), and hydrogen-3 (tritium)\|alt=Diagram showing the structure of each of Hydrogen-1 (mass number 1, 1 electron, 1 proton), Hydrogen-2 or deuterium (mass number 2, 1 electron, 1 proton, 1 neutron), and Hydrogen-3 or tritium (mass number 3, 1 electron, 1 proton, 2 neutrons)]]
	Hydrogen has three naturally-occurring isotopes, ~~denoted~~ , and{~~{nbsp}~~}. Other, highly-unstable nuclides~~{{nbsp}}( to )~~ have been synthesized in laboratories but not observed in nature.<ref name="Gurov">{{cite journal		Hydrogen has three naturally-occurring isotopes: protium (<math>^1\mathrm{H}</math>), deuterium (<math>^2\mathrm{H}</math> or D), and tritium (<math>^3\mathrm{H}</math> or T). Other highly unstable hydrogen nuclides have been synthesized in laboratories but not observed in nature.<ref name="Gurov">{{cite journal
	\|author=Gurov, Y. B.		\|author=Gurov, Y. B.
	\|author2=Aleshkin, D. V.		\|author2=Aleshkin, D. V.

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	'''Hydrogen''' is a chemical element; it has the symbol{{nbsp}}'''H''' and atomic number{{nbsp}}1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatomic molecules with the formula{{nbsp}}{{chem2\|H2}}, called '''dihydrogen'''<!--dihydrogen is a redirect to hydrogen; also called '''diprotium'''-->, or sometimes '''hydrogen gas''', '''molecular hydrogen''', or simply hydrogen. Dihydrogen is colorless, odorless, non-toxic, and highly combustible. Stars, including the Sun, mainly consist of hydrogen in a plasma state, while on Earth, hydrogen is found as the gas{{nbsp}}{{chem2\|H2}} (dihydrogen) and in molecules, such as in water and organic compounds. The most common isotope of hydrogen, H, consists of one proton, one electron, and no neutrons.		'''Hydrogen''' is a chemical element; it has the symbol{{nbsp}}'''H''' and atomic number{{nbsp}}1. It is the lightest and most abundant chemical element in the universe, constituting about 75% of all normal matter. Under standard conditions, hydrogen is a gas of diatomic molecules with the formula{{nbsp}}{{chem2\|H2}}, called '''dihydrogen'''<!--dihydrogen is a redirect to hydrogen; also called '''diprotium'''-->, or sometimes '''hydrogen gas''', '''molecular hydrogen''', or simply hydrogen. Dihydrogen is colorless, odorless, non-toxic, and highly combustible. Stars, including the Sun, mainly consist of hydrogen in a plasma state, while on Earth, hydrogen is found as the gas{{nbsp}}{{chem2\|H2}} (dihydrogen) and in molecules, such as in water and organic compounds. The most common isotope of hydrogen, H, consists of one proton, one electron, and no neutrons.

	Hydrogen gas was first produced artificially in the 17th{{nbsp}}century by the reaction of acids with metals. Henry Cavendish, in{{nbsp}}1766–1781, identified hydrogen gas as a distinct substance and discovered its property of producing water when burned: this is the origin of hydrogen's name, which means (from ~~{{langx\|grc\|ὕδωρ\|~~húdōr\|water}}, and ~~{{langx\|grc\|γεννάω\|~~gennáō\|I bring forth~~\|label=none}}~~). Understanding the colors of light absorbed and emitted by hydrogen was a crucial part of the development of [[Physics:Quantum mechanics\|quantum mechanics]].		Hydrogen gas was first produced artificially in the 17th{{nbsp}}century by the reaction of acids with metals. Henry Cavendish, in{{nbsp}}1766–1781, identified hydrogen gas as a distinct substance and discovered its property of producing water when burned: this is the origin of hydrogen's name, which means (from Ancient Greek ''húdōr'', "water", and ''gennáō'', "I bring forth"). Understanding the colors of light absorbed and emitted by hydrogen was a crucial part of the development of [[Physics:Quantum mechanics\|quantum mechanics]].

	Hydrogen, typically nonmetallic except under extreme pressure, readily forms covalent bonds with most nonmetals, contributing to the formation of compounds like water and various organic substances. Its role is crucial in acid–base reactions, which mainly involve proton exchange among soluble molecules. In ionic compounds, hydrogen can take the form of either a negatively-charged anion, where it is known as hydride, or as a positively charged cation, {{chem2\|H+}}, hydron. Although tightly bonded to water molecules, hydrons strongly affect the behavior of aqueous solutions, as reflected in the importance of pH. Hydride, on the other hand, is rarely observed because it tends to deprotonate solvents, yielding{{nbsp}}{{chem2\|H2}}.<ref>{{Cite web \|title=Element: Hydrogen \|url=https://pse-info.de/en/element/H \|access-date=2026-01-21 \|website=Periodic table \|language=en}}</ref>		Hydrogen, typically nonmetallic except under extreme pressure, readily forms covalent bonds with most nonmetals, contributing to the formation of compounds like water and various organic substances. Its role is crucial in acid–base reactions, which mainly involve proton exchange among soluble molecules. In ionic compounds, hydrogen can take the form of either a negatively-charged anion, where it is known as hydride, or as a positively charged cation, {{chem2\|H+}}, hydron. Although tightly bonded to water molecules, hydrons strongly affect the behavior of aqueous solutions, as reflected in the importance of pH. Hydride, on the other hand, is rarely observed because it tends to deprotonate solvents, yielding{{nbsp}}{{chem2\|H2}}.<ref>{{Cite web \|title=Element: Hydrogen \|url=https://pse-info.de/en/element/H \|access-date=2026-01-21 \|website=Periodic table \|language=en}}</ref>