Editing Oxide (section)

==Formation==
Oxides are associated with all elements except a few noble gases. The pathways for the formation of this diverse family of compounds are correspondingly numerous.

===Metal oxides===
Many metal oxides arise by decomposition of other metal compounds, e.g. [[carbonate]]s, [[hydroxide]]s, and [[nitrate]]s.  In the making of [[calcium oxide]], [[calcium carbonate]] ([[limestone]]) breaks down upon heating, releasing carbon dioxide:<ref name=Greenwood/><!--p120-->
:<chem>CaCO3  ->  CaO  +  CO2</chem>
The reaction of elements with oxygen in air is a key step in [[corrosion]] relevant to the commercial use of iron especially. Almost all elements form oxides upon heating with oxygen atmosphere. For example, zinc powder will burn in air to give [[zinc oxide]]:<ref>{{cite book |doi=10.1002/14356007.a28_509|chapter=Zinc |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Graf |first1=Günter G. |isbn=3-527-30673-0 }}</ref>
:<chem>2 Zn  + O2  ->  2 ZnO</chem>
The production of metals from ores often involves the production of oxides by roasting (heating) metal sulfide minerals in air. In this way, {{chem2|MoS2}} ([[molybdenite]]) is converted to [[molybdenum trioxide]], the precursor to virtually all molybdenum compounds:<ref>{{Ullmann|author=Roger F. Sebenik|display-authors=etal|title=Molybdenum and Molybdenum Compounds|year=2005|doi=10.1002/14356007.a16_655|isbn=978-3527306732}}</ref>
:<chem>2 MoS2  +  7 O2  ->  2MoO3  +  4 SO2</chem>

[[Noble metal]]s (such as [[gold]] and [[platinum]]) are prized because they resist direct chemical combination with oxygen.<ref name=Greenwood/>

===Non-metal oxides===
Important and prevalent nonmetal oxides are [[carbon dioxide]] and [[carbon monoxide]].  These species form upon full or partial oxidation of carbon or hydrocarbons.  With a deficiency of oxygen, the monoxide is produced:<ref name=Greenwood/>
:<chem>2 CH4  + 3 O2  -> 2 CO  +  4  H2O</chem>
:<chem>2 C  +  O2  -> 2 CO</chem>
With excess oxygen, the dioxide is the product, the pathway proceeds by the intermediacy of carbon monoxide:
:<chem>CH4  + 2 O2  ->  CO2  +  2 H2O</chem>
:<chem>C + O2  ->  CO2</chem>

Elemental nitrogen ({{chem2|N2}}) is difficult to convert to oxides, but the combustion of ammonia gives [[nitric oxide]], which further reacts with oxygen:
:<chem>4 NH3  + 5 O2  ->  4 NO  +  6 H2O</chem>
:<chem>2 NO  +  O2  -> 2 NO2</chem>
These reactions are practiced in the production of [[nitric acid]], a commodity chemical.<ref name=Ullmann>{{Ullmann|last1=Thiemann |first1=Michael |last2=Scheibler |first2=Erich |last3=Wiegand |first3=Karl Wilhelm |date=2000 |title=Nitric Acid, Nitrous Acid, and Nitrogen Oxides |doi=10.1002/14356007.a17_293|isbn=978-3527306732 }}</ref>

The chemical produced on the largest scale industrially is [[sulfuric acid]].  It is produced by the oxidation of sulfur to [[sulfur dioxide]], which is separately oxidized to [[sulfur trioxide]]:<ref>{{Ullmann|doi=10.1002/14356007.a25_635|title=Sulfuric Acid and Sulfur Trioxide |year=2000 |last1=Müller |first1=Hermann |isbn=3527306730 }}</ref> 
:<chem>S + O2  -> SO2</chem>
:<chem>2 SO2 +  O2  -> 2 SO3</chem>
Finally the trioxide is converted to sulfuric acid by a [[hydration reaction]]:
:<chem>SO3 + H2O  -> H2SO4</chem>