Oxygen - Revision history

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energy>Luisa at 22:20, 9 September 2021

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			[[es:Oxígeno]]
	[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]		[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]

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2017-08-29T01:47:39Z

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Jmdonev at 01:58, 28 August 2017

2017-08-28T01:58:40Z

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	[[Category:Done ~~2016~~-12-31]]		[[Category:Done 2017-07-01]]
	[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]		[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]

	<onlyinclude>'''Oxygen''' is the 8<sup>th</sup> [[element]] on the [[periodic table of elements\|periodic table]], and is the 3<sup>rd</sup> most abundant element in the universe.<ref>Periodic Table, ''Abundance in the Universe'' [Online], Available: http://periodictable.com/Properties/A/UniverseAbundance.v.log.html</ref> Although the amount of oxygen in the universe is dwarfed by [[hydrogen]] and [[helium]], oxygen is the most common element on Earth, and it is a crucial component of life.</onlyinclude><ref>Periodic Table, ''Abundance in the Ocean'' [Online], Available: http://periodictable.com/Properties/A/OceanAbundance.v.log.html</ref> Plants release oxygen in the process of [[photosynthesis]], and humans and other animals intake the oxygen when they breathe. Oxygen makes up 46% of the [[cross section of the Earth\|Earth's crust]], with [[silicon]] making up 27%, so unsurprisingly the most abundant minerals present on Earth are a combination of the two, known as silicates.<ref>Hyperphysics, ''Element Abundance in the Earth's Crust'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/tables/elabund.html</ref>		<onlyinclude>'''Oxygen''' is the 8<sup>th</sup> [[element]] on the [[periodic table of elements\|periodic table]], and is the 3<sup>rd</sup> most abundant element in the universe.<ref>Periodic Table, ''Abundance in the Universe'' [Online], Available: http://periodictable.com/Properties/A/UniverseAbundance.v.log.html</ref> Although the amount of oxygen in the universe is dwarfed by [[hydrogen]] and [[helium]], oxygen is the most common element on Earth, and it is a crucial component of life.</onlyinclude><ref>Periodic Table, ''Abundance in the Ocean'' [Online], Available: http://periodictable.com/Properties/A/OceanAbundance.v.log.html</ref>

	~~Some properties of~~ oxygen ~~include:~~<~~ref~~>~~Periodic Table, ''Technical data for Oxygen'' [Online], Available: http://periodictable.com/Elements/008/data.html~~</~~ref~~>		Oxygen exists in two elemental forms: [[molecular oxygen]] (O<sub>2</sub>) and [[ozone]] (O<sub>3</sub>). It also exists in countless compounds with other elements. Compounds of oxygen are called ''oxides''. Some examples of common oxides are minerals such as granite and quartz (oxides of silicon), rust (oxides of iron), and limestone (oxide of calcium and carbon). Many organic compounds also contain oxygen atoms in their structure. Read more about the chemistry of oxygen at the [https://chem.libretexts.org/Core/Inorganic_Chemistry/Descriptive_Chemistry/Elements_Organized_by_Block/2_p-Block_Elements/Group_16%3A_The_Oxygen_Family_(The_Chalcogens)/Z%3D008_Chemistry_of_Oxygen_(Z%3D8) Chemistry LibreText].

	~~{\| class="wikitable"~~
	\|-
	~~\| '''~~[[~~Atomic weight~~]]~~''' \|\| 15.9994~~
	\|-
	~~\| '''[[Density]]'''~~ (~~at 0~~<~~sup~~>o</~~sup~~>C) ~~\|\| 1~~.~~429 [[gram\|g]]/[[liter\|L]]~~
	\|-
	\| '''~~[[Boiling point]]~~'~~'' \|\| 90~~.2 [~~[Kelvin\|K]]~~
	\|-
	~~\| '''[[Melting point~~]~~]''' \|\| 54~~.~~8 K~~
	\|}

	==Oxygen on Earth==		==Oxygen on Earth==
			[[File:ocken.jpg\|800px\|center\|thumb\|Figure 2. Oxygen makes up a large part of the world we live in, both the ground and sky.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/0/0d/Iss007e10807.jpg</ref>]]
			Oxygen makes up 46% of the [[cross section of the Earth\|Earth's crust]], largely as ''silicates'', compounds of oxygen and [[silicon]]. <ref>Hyperphysics, ''Element Abundance in the Earth's Crust'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/tables/elabund.html</ref> Oxygen also comprises around 21% of the [[atmospheric oxygen\|atmosphere]] as [[molecular oxygen]] and [[ozone]].

	~~Oxygen~~ is ~~by far~~ the ~~most common element on~~ Earth, ~~making up around 21%~~ of the [[atmosphere]], ~~90% of~~ the ~~Ocean and two thirds~~ of the ~~human body.<ref>Jefferson Lab, ''The element oxygen'~~' [~~Online~~]~~, Available: http://education~~.~~jlab.org/itselemental/ele008.html</ref> However free oxygen wasn't always present~~ in the atmosphere, ~~and around 2~~.~~5 billion years ago~~ the only life on Earth were very small bacteria that didn't require oxygen to live.<ref>NASA, ''NASA Research Indicates OXygen on Earth 2.5 Billion Years Ago'' [Online], Available: http://www.nasa.gov/home/hqnews/2007/sep/HQ_07215_Timeline_of_Oxygen_on_Earth.html</ref> These organisms were in fact poisoned by oxygen, so when a ~~photosynthetic life form called cyanobacteria began to flourish by converting~~ [[~~sunlight~~]] ~~into [[energy]] and producing oxygen, the other life-forms began to die off~~.<ref>~~Bad Astronomy~~, ''~~Poisoned Planet~~'' [Online], Available: http://~~www~~.~~slate~~.~~com/blogs/bad_astronomy/2014/07~~/28/~~the_great_oxygenation_event_the_earth_s_first_mass_extinction~~.html</ref> ~~This is known as the Great Oxygenation Event, and made way for the life-forms of today. For more information visit our page on [[atmospheric oxygen]].~~		[[Ozone]] (O<sub>3</sub>) is a pollutant near the Earth's surface, but is a vital component of the [[layers of the atmosphere\|stratosphere]], as it forms the [[ozone layer]] - a blanket of ozone that shields the planet's surface from [[ultraviolet radiation]]. Ozone forms naturally in the atmosphere, but can be destroyed by reaction with certain pollutants. In some areas, the depletion of ozone has created an "ozone hole" - a serious concern for the [[environment]].<ref>NASA, ''Ozone Hole Watch: Facts about ozone'' [Online], Available: http://ozonewatch.gsfc.nasa.gov/facts/SH.html</ref>

	[[File:ocken.jpg\|815px\|center\|thumb\|Figure 2. Oxygen makes up a large part of the world we live in, both the ground and sky.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/0/0d/Iss007e10807.jpg</ref>]]

	~~Oxygen is found in many forms on Earth, most commonly bonded with [[hydrogen]] to form H~~<sub>2</sub>O, [[~~water~~]], but is also a key part of other molecules important to life. Oxygen combines with almost every other element to form "oxides": For example it combines with silicon in the Earth's crust to form silicon dioxide found in granite and quartz, with iron to form iron oxide found in rust, and with calcium and [[~~carbon~~]] to ~~form calcium carbonate found in limestone. Visit~~ [~~http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/p-Block_Elements/Group_16%3A_The_Oxygen_Family/Chemistry_of_Oxygen UC Davis' ChemWiki~~] ~~to learn more about how oxygen interacts with the other elements~~.		Molecular oxygen (as O<sub>2</sub>) is essential for life. Many organisms require oxygen for metabolism, and [[photosynthesis\|photosynthetic]] plants produce oxygen as they convert [[sunlight]] to stored [[energy]].

	~~Aside from oxygen's role in the chemistry of life, a different form of oxygen is also vitally important on our planet.~~ [[~~Ozone~~]] ~~(O<sub>3</sub>)~~ is ~~found in the upper~~ [[~~layers of the atmosphere~~]]~~, forming a thin layer around~~ the ~~Earth, known as the [[Ozone layer]]. It is important because it absorbs most~~ of ~~the~~ [[~~Sun~~]]'s [[~~ultraviolet radiation~~]] ~~that is harmful to life~~. ~~Ozone~~ is ~~created when [[molecular oxygen]] (O<sub>2</sub>) is split apart by sunlight into single oxygen atoms~~, which ~~then recombine to form ozone. Ozone~~ is ~~destroyed when it reacts with certain molecules~~, ~~some of which are put into the atmosphere by humans. The destruction of ozone caused by humans is contributing~~ to ~~the known "ozone hole" which is a big concern.<ref>NASA, ''Ozone Hole Watch: Facts about ozone'' [Online], Available: http://ozonewatch.gsfc.nasa.gov/facts/SH~~.~~html</ref>~~		==Oxygen and Combustion==
			[[Molecular oxygen]] is important for [[combustion]] - especially in the combustion of [[fuel]]s for [[energy]]. Combustion is the reaction of a compound with an oxidant, which is usually molecular oxygen, to produce oxides.

	~~==Oxygen~~ in combustion==		Combustion of [[fossil fuel]]s such as [[methane]], shown in Figure 3 below, produces [[carbon dioxide]], [[water vapour]], and energy. Fossil fuel combustion supplies around 95% of the world's [[primary energy]].

	Oxygen is important for its role in the burning of [[fuel]]s, which is a large focus on this encyclopedia. [[Fossil fuel]]s such as [[methane]] go through the process of [[hydrocarbon combustion\|combustion]] in which they react with oxygen, which produces [[carbon dioxide]], [[water vapour]] and [[heat]] as shown in Figure 3. This process supplies the world with most of its [[primary energy]] - around 95%.<ref>OECD data, visit [[primary energy]] for more detail.</ref> This process is actually quite fascinating; dead plants and animals are what make the fossil fuels, live plants are what make the oxygen, and the result is energy for human's needs.

	[[File:combustion_of_methane.jpg\|800px\|thumbnail\|center\|Figure 1. Methane ~~combining~~ with 2 oxygen to form carbon dioxide, water and heat.<ref name="image">American Chemical Society. "Methane and oxygen react". Internet: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]</ref>]]		[[File:combustion_of_methane.jpg\|800px\|thumbnail\|center\|Figure 3. Methane reacting with oxygen to form carbon dioxide, water and heat.<ref name="image">American Chemical Society. "Methane and oxygen react". Internet: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]</ref>]]

	==Video==		==Video==
	The video below is from the University of Nottingham's [http://www.periodicvideos.com/ ~~periodic videos~~ project].<ref>See more videos from the University of Nottingham on different elements here: http://www.periodicvideos.com/</ref> ~~They have created a complete suite of short videos on every element on the [[periodic table of elements]].~~ This video talks about oxygen, but also discusses [[ozone]].		The video below is from the University of Nottingham's [http://www.periodicvideos.com/ Periodic Videos project].<ref>See more videos from the University of Nottingham on different elements here: http://www.periodicvideos.com/</ref> This video talks about oxygen, but also discusses [[ozone]].

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Jmdonev: 1 revision imported

2017-01-08T23:36:27Z

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Jmdonev at 20:46, 20 November 2016

2016-11-20T20:46:49Z

← Older revision		Revision as of 20:46, 20 November 2016
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	[[Category:Done ~~2015~~-09-06]]		[[Category:Done 2016-12-31]]
	[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]		[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]

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	[[File:combustion_of_methane.jpg\|800px\|thumbnail\|center\|Figure 1. Methane combining with 2 oxygen to form carbon dioxide, water and heat.<ref name="image">American Chemical Society. "Methane and oxygen react". Internet: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]</ref>]]		[[File:combustion_of_methane.jpg\|800px\|thumbnail\|center\|Figure 1. Methane combining with 2 oxygen to form carbon dioxide, water and heat.<ref name="image">American Chemical Society. "Methane and oxygen react". Internet: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]</ref>]]

			==Video==
			The video below is from the University of Nottingham's [http://www.periodicvideos.com/ periodic videos project].<ref>See more videos from the University of Nottingham on different elements here: http://www.periodicvideos.com/</ref> They have created a complete suite of short videos on every element on the [[periodic table of elements]]. This video talks about oxygen, but also discusses [[ozone]].

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			<iframe width="816" height="459" src="https://www.youtube.com/embed/WuG5WTId-IY" frameborder="0" allowfullscreen></iframe>
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	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]
			[[category: Ian edit]]

J.williams: 1 revision imported

2015-09-18T16:51:29Z

1 revision imported

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Jhanania at 20:50, 3 September 2015

2015-09-03T20:50:10Z

← Older revision		Revision as of 20:50, 3 September 2015
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	[[Category:Done 2015-07-01]]		[[Category:Done 2015-09-06]]
	[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]		[[File:OXYGEN.png\|200px\|thumb\|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]

	<onlyinclude>'''Oxygen''' is the 8<sup>th</sup> [[element]] on the [[periodic table of elements\|periodic table]], and is the 3<sup>rd</sup> most abundant element in the universe.<ref>Periodic Table, ''Abundance in the Universe'' [Online], Available: http://periodictable.com/Properties/A/UniverseAbundance.v.log.html</ref> Although the amount of oxygen in the universe is dwarfed by [[hydrogen]] and helium, oxygen is the most common element on Earth, and it is a crucial component of life.</onlyinclude><ref>Periodic Table, ''Abundance in the Ocean'' [Online], Available: http://periodictable.com/Properties/A/OceanAbundance.v.log.html</ref> Plants release oxygen in the process of [[photosynthesis]], and humans and other animals intake the oxygen when they breathe. Oxygen makes up 46% of the [[cross section of the Earth\|Earth's crust]], with [[silicon]] making up 27%, so unsurprisingly the most abundant minerals present on Earth are a combination of the two, known as silicates.<ref>Hyperphysics, ''Element Abundance in the Earth's Crust'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/tables/elabund.html</ref>		<onlyinclude>'''Oxygen''' is the 8<sup>th</sup> [[element]] on the [[periodic table of elements\|periodic table]], and is the 3<sup>rd</sup> most abundant element in the universe.<ref>Periodic Table, ''Abundance in the Universe'' [Online], Available: http://periodictable.com/Properties/A/UniverseAbundance.v.log.html</ref> Although the amount of oxygen in the universe is dwarfed by [[hydrogen]] and [[helium]], oxygen is the most common element on Earth, and it is a crucial component of life.</onlyinclude><ref>Periodic Table, ''Abundance in the Ocean'' [Online], Available: http://periodictable.com/Properties/A/OceanAbundance.v.log.html</ref> Plants release oxygen in the process of [[photosynthesis]], and humans and other animals intake the oxygen when they breathe. Oxygen makes up 46% of the [[cross section of the Earth\|Earth's crust]], with [[silicon]] making up 27%, so unsurprisingly the most abundant minerals present on Earth are a combination of the two, known as silicates.<ref>Hyperphysics, ''Element Abundance in the Earth's Crust'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/tables/elabund.html</ref>

	Some properties of oxygen include:<ref>Periodic Table, ''Technical data for Oxygen'' [Online], Available: http://periodictable.com/Elements/008/data.html</ref>		Some properties of oxygen include:<ref>Periodic Table, ''Technical data for Oxygen'' [Online], Available: http://periodictable.com/Elements/008/data.html</ref>
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	==Oxygen on Earth==		==Oxygen on Earth==

	Oxygen is by far the most common element on Earth, making up around 21% of the [[atmosphere]], 90% of the Ocean and two thirds of the human body.<ref>Jefferson Lab, ''The element oxygen'' [Online], Available: http://education.jlab.org/itselemental/ele008.html</ref> However free oxygen wasn't always present in the atmosphere, and around 2.5 billion years ago the only life on Earth were very small bacteria that didn't require oxygen to live.<ref>NASA, ''NASA Research Indicates OXygen on Earth 2.5 Billion Years Ago'' [Online], Available: http://www.nasa.gov/home/hqnews/2007/sep/HQ_07215_Timeline_of_Oxygen_on_Earth.html</ref> These organisms were in fact poisoned by oxygen, so when a photosynthetic life form called cyanobacteria began to flourish by converting sunlight into energy and producing oxygen, the other life-forms began to die off.<ref>Bad Astronomy, ''Poisoned Planet'' [Online], Available: http://www.slate.com/blogs/bad_astronomy/2014/07/28/the_great_oxygenation_event_the_earth_s_first_mass_extinction.html</ref> This is known as the Great Oxygenation Event, and made way for the life-forms of today. For more information visit our page on [[atmospheric oxygen]].		Oxygen is by far the most common element on Earth, making up around 21% of the [[atmosphere]], 90% of the Ocean and two thirds of the human body.<ref>Jefferson Lab, ''The element oxygen'' [Online], Available: http://education.jlab.org/itselemental/ele008.html</ref> However free oxygen wasn't always present in the atmosphere, and around 2.5 billion years ago the only life on Earth were very small bacteria that didn't require oxygen to live.<ref>NASA, ''NASA Research Indicates OXygen on Earth 2.5 Billion Years Ago'' [Online], Available: http://www.nasa.gov/home/hqnews/2007/sep/HQ_07215_Timeline_of_Oxygen_on_Earth.html</ref> These organisms were in fact poisoned by oxygen, so when a photosynthetic life form called cyanobacteria began to flourish by converting [[sunlight]] into [[energy]] and producing oxygen, the other life-forms began to die off.<ref>Bad Astronomy, ''Poisoned Planet'' [Online], Available: http://www.slate.com/blogs/bad_astronomy/2014/07/28/the_great_oxygenation_event_the_earth_s_first_mass_extinction.html</ref> This is known as the Great Oxygenation Event, and made way for the life-forms of today. For more information visit our page on [[atmospheric oxygen]].

	[[File:ocken.jpg\|815px\|center\|thumb\|Figure 2. Oxygen makes up a large part of the world we live in, both the ground and sky.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/0/0d/Iss007e10807.jpg</ref>]]		[[File:ocken.jpg\|815px\|center\|thumb\|Figure 2. Oxygen makes up a large part of the world we live in, both the ground and sky.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/0/0d/Iss007e10807.jpg</ref>]]

	Oxygen is found in many forms on Earth, most commonly bonded with [[hydrogen]] to form H<sub>2</sub>O, [[water]], but is also a key part of other molecules important to life. Oxygen combines with almost every other element to form "oxides": For example it combines with silicon in the Earth's crust to form silicon dioxide found in granite and quartz, with iron to form iron oxide found in rust, and with calcium and carbon to form calcium carbonate found in limestone. Visit [http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/p-Block_Elements/Group_16%3A_The_Oxygen_Family/Chemistry_of_Oxygen UC Davis' ChemWiki] to learn more about how oxygen interacts with the other elements.		Oxygen is found in many forms on Earth, most commonly bonded with [[hydrogen]] to form H<sub>2</sub>O, [[water]], but is also a key part of other molecules important to life. Oxygen combines with almost every other element to form "oxides": For example it combines with silicon in the Earth's crust to form silicon dioxide found in granite and quartz, with iron to form iron oxide found in rust, and with calcium and [[carbon]] to form calcium carbonate found in limestone. Visit [http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/p-Block_Elements/Group_16%3A_The_Oxygen_Family/Chemistry_of_Oxygen UC Davis' ChemWiki] to learn more about how oxygen interacts with the other elements.

	Aside from oxygen's role in the chemistry of life, a different form of oxygen is also vitally important on our planet. [[Ozone]] (O<sub>3</sub>) is found in the upper [[layers of the atmosphere]], forming a thin layer around the Earth, known as the [[Ozone layer]]. It is important because it absorbs most of the [[Sun]]'s [[ultraviolet radiation]] that is harmful to life. Ozone is created when [[molecular oxygen]] (O<sub>2</sub>) is split apart by sunlight into single oxygen atoms, which then recombine to form ozone. Ozone is destroyed when it reacts with certain molecules, some of which are put into the atmosphere by humans. The destruction of ozone caused by humans is contributing to the known "ozone hole" which is a big concern.<ref>NASA, ''Ozone Hole Watch: Facts about ozone'' [Online], Available: http://ozonewatch.gsfc.nasa.gov/facts/SH.html</ref>		Aside from oxygen's role in the chemistry of life, a different form of oxygen is also vitally important on our planet. [[Ozone]] (O<sub>3</sub>) is found in the upper [[layers of the atmosphere]], forming a thin layer around the Earth, known as the [[Ozone layer]]. It is important because it absorbs most of the [[Sun]]'s [[ultraviolet radiation]] that is harmful to life. Ozone is created when [[molecular oxygen]] (O<sub>2</sub>) is split apart by sunlight into single oxygen atoms, which then recombine to form ozone. Ozone is destroyed when it reacts with certain molecules, some of which are put into the atmosphere by humans. The destruction of ozone caused by humans is contributing to the known "ozone hole" which is a big concern.<ref>NASA, ''Ozone Hole Watch: Facts about ozone'' [Online], Available: http://ozonewatch.gsfc.nasa.gov/facts/SH.html</ref>

J.williams: 1 revision imported

2015-08-26T21:31:28Z

1 revision imported

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J.williams at 16:58, 12 August 2015

2015-08-12T16:58:19Z

New page

[[Category:Done 2015-07-01]]
[[File:OXYGEN.png|200px|thumb|Figure 1. Oxygen, [[atomic number]] of 8 and [[atomic weight]] of 15.9994.<Ref>Made internally be a member of the Energy Education team, with information from periodictable.com, Available: http://periodictable.com/Elements/008/index.html</ref>]]

<onlyinclude>'''Oxygen''' is the 8th [[element]] on the [[periodic table of elements|periodic table]], and is the 3rd most abundant element in the universe.<ref>Periodic Table, ''Abundance in the Universe'' [Online], Available: http://periodictable.com/Properties/A/UniverseAbundance.v.log.html</ref> Although the amount of oxygen in the universe is dwarfed by [[hydrogen]] and helium, oxygen is the most common element on Earth, and it is a crucial component of life.</onlyinclude><ref>Periodic Table, ''Abundance in the Ocean'' [Online], Available: http://periodictable.com/Properties/A/OceanAbundance.v.log.html</ref> Plants release oxygen in the process of [[photosynthesis]], and humans and other animals intake the oxygen when they breathe. Oxygen makes up 46% of the [[cross section of the Earth|Earth's crust]], with [[silicon]] making up 27%, so unsurprisingly the most abundant minerals present on Earth are a combination of the two, known as silicates.<ref>Hyperphysics, ''Element Abundance in the Earth's Crust'' [Online], Available: http://hyperphysics.phy-astr.gsu.edu/hbase/tables/elabund.html</ref>

Some properties of oxygen include:<ref>Periodic Table, ''Technical data for Oxygen'' [Online], Available: http://periodictable.com/Elements/008/data.html</ref>

{| class="wikitable"
|-
| '''[[Atomic weight]]''' || 15.9994
|-
| '''[[Density]]''' (at 0oC) || 1.429 [[gram|g]]/[[liter|L]]
|-
| '''[[Boiling point]]''' || 90.2 [[Kelvin|K]]
|-
| '''[[Melting point]]''' || 54.8 K
|}

==Oxygen on Earth==

Oxygen is by far the most common element on Earth, making up around 21% of the [[atmosphere]], 90% of the Ocean and two thirds of the human body.<ref>Jefferson Lab, ''The element oxygen'' [Online], Available: http://education.jlab.org/itselemental/ele008.html</ref> However free oxygen wasn't always present in the atmosphere, and around 2.5 billion years ago the only life on Earth were very small bacteria that didn't require oxygen to live.<ref>NASA, ''NASA Research Indicates OXygen on Earth 2.5 Billion Years Ago'' [Online], Available: http://www.nasa.gov/home/hqnews/2007/sep/HQ_07215_Timeline_of_Oxygen_on_Earth.html</ref> These organisms were in fact poisoned by oxygen, so when a photosynthetic life form called cyanobacteria began to flourish by converting sunlight into energy and producing oxygen, the other life-forms began to die off.<ref>Bad Astronomy, ''Poisoned Planet'' [Online], Available: http://www.slate.com/blogs/bad_astronomy/2014/07/28/the_great_oxygenation_event_the_earth_s_first_mass_extinction.html</ref> This is known as the Great Oxygenation Event, and made way for the life-forms of today. For more information visit our page on [[atmospheric oxygen]].

[[File:ocken.jpg|815px|center|thumb|Figure 2. Oxygen makes up a large part of the world we live in, both the ground and sky.<ref>Wikimedia Commons [Online], Available: http://upload.wikimedia.org/wikipedia/commons/0/0d/Iss007e10807.jpg</ref>]]

Oxygen is found in many forms on Earth, most commonly bonded with [[hydrogen]] to form H2O, [[water]], but is also a key part of other molecules important to life. Oxygen combines with almost every other element to form "oxides": For example it combines with silicon in the Earth's crust to form silicon dioxide found in granite and quartz, with iron to form iron oxide found in rust, and with calcium and carbon to form calcium carbonate found in limestone. Visit [http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Descriptive_Chemistry/p-Block_Elements/Group_16%3A_The_Oxygen_Family/Chemistry_of_Oxygen UC Davis' ChemWiki] to learn more about how oxygen interacts with the other elements.

Aside from oxygen's role in the chemistry of life, a different form of oxygen is also vitally important on our planet. [[Ozone]] (O3) is found in the upper [[layers of the atmosphere]], forming a thin layer around the Earth, known as the [[Ozone layer]]. It is important because it absorbs most of the [[Sun]]'s [[ultraviolet radiation]] that is harmful to life. Ozone is created when [[molecular oxygen]] (O2) is split apart by sunlight into single oxygen atoms, which then recombine to form ozone. Ozone is destroyed when it reacts with certain molecules, some of which are put into the atmosphere by humans. The destruction of ozone caused by humans is contributing to the known "ozone hole" which is a big concern.<ref>NASA, ''Ozone Hole Watch: Facts about ozone'' [Online], Available: http://ozonewatch.gsfc.nasa.gov/facts/SH.html</ref>

==Oxygen in combustion==

Oxygen is important for its role in the burning of [[fuel]]s, which is a large focus on this encyclopedia. [[Fossil fuel]]s such as [[methane]] go through the process of [[hydrocarbon combustion|combustion]] in which they react with oxygen, which produces [[carbon dioxide]], [[water vapour]] and [[heat]] as shown in Figure 3. This process supplies the world with most of its [[primary energy]] - around 95%.<ref>OECD data, visit [[primary energy]] for more detail.</ref> This process is actually quite fascinating; dead plants and animals are what make the fossil fuels, live plants are what make the oxygen, and the result is energy for human's needs.

[[File:combustion_of_methane.jpg|800px|thumbnail|center|Figure 1. Methane combining with 2 oxygen to form carbon dioxide, water and heat.<ref name="image">American Chemical Society. "Methane and oxygen react". Internet: http://www.middleschoolchemistry.com/multimedia/chapter6/lesson1, [October 25,2013]</ref>]]

==References==
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