Editing Oxide (section)

===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/>