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| | {{Element | name=Oxygen | symbol=O | anumber=8 | amass=16.0 amu | state=gas | class=Non-metal | cstructure=Cubic | color=Colorless | date=1774 | discname=[[Joseph Priestley]] | origname=From the Greek words ''oxus'' (acid) and ''gennan'' (generate) | uses=Supports life | obtained=From liquid air}} | | {{Element | name=Oxygen | symbol=O | anumber=8 | amass=16.0 amu | state=gas | class=Non-metal | cstructure=Cubic | color=Colorless | date=1774 | discname=[[Joseph Priestley]] | origname=From the Greek words ''oxus'' (acid) and ''gennan'' (generate) | uses=Supports life | obtained=From liquid air}} |
| − | '''Oxygen''' is a [[chemical]] [[element]] with 8 [[proton]]s.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> Oxygen's [[atomic mass]] is slightly under 16, since it also has 8 [[neutron]]s (a slight amount of mass is "lost" in the energy contained in the [[subatomic bond]]s).
| + | Oxygen is the third most abundant element in the universe by mass and is essential to life on Earth. |
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| − | The name "oxygen" means "acid maker": Many common acids -- nitric, sulfuric, phosphoric, etc. -- are just hydrogen nitrate, hydrogen sulfate, or hydrogen phosphate, where the nitrate, sulfate, and phosphate complexes involve oxygen.
| + | ==Chemical Properties== |
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| − | Under normal conditions oxygen is a colorless, odorless [[gas]] consisting of two oxygen [[atom|atoms]] which has the chemical formula O<sub>2</sub>. This means it is [[diatom]]ic. Approximately 20% of the [[atmosphere]] is made up of oxygen. Oxygen also forms a [[triatomic]] molecule called [[ozone]] (O<sub>3</sub>), which, although unstable under normal conditions, is a very important ingredient in the upper [[atmosphere]], forming a layer which blocks most of the [[Sun]]'s [[ultraviolet]] radiation.
| + | At normal atmospheric pressure oxygen melts at 54.36 [[Kelvin]] (K) and boils at 90.2 K; on Earth it essentially exists only as a gas. It readily dissolves in water, which makes aquatic life possible. Under normal conditions oxygen forms molecules consisting of two oxygen atoms each sharing two electrons in the 2p subshell; this form of oxygen is known as O<sub>2</sub>. O<sub>2</sub> is a pale blue odourless gas. |
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| − | Oxygen is highly reactive, and in many other elements and compounds undergo [[exothermic reaction]]s with it (they [[combustion|burn]] or [[oxidation|rust]]). If it were not for its continual replenishment as a waste product of plant [[photosynthesis]], all atmospheric oxygen would disappear, forming compounds with other chemicals at the earth's surface.
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| − | Many [[animal]]s depend upon oxygen as a highly efficient ingredient for breaking down [[food]] for [[energy]], due to its reactivity. Those that do not are called "[[anaerobic]]", meaning "without air", and include many important [[bacteria]].
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| − | {{periodic table}}
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| − | ==References==
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| − | <references/>
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