Changes

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.

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.

Under normal conditions it is a colorless, odorless [[gas]] consisting of two oxygen [[atom|atoms]] which has the chemical formula O₂. This means it is [[diatom]]ic.  Approximately 20% of the [[atmosphere]] is made up of oxygen.  Oxygen also forms a [[triatomic]] molecule called [[ozone]] (O₃), which although unstable under normal conditions, is a very important ingredient in the upper [[atmosphere]].

Under normal conditions oxygen is a colorless, odorless [[gas]] consisting of two oxygen [[atom|atoms]] which has the chemical formula O₂. This means it is [[diatom]]ic.  Approximately 20% of the [[atmosphere]] is made up of oxygen.  Oxygen also forms a [[triatomic]] molecule called [[ozone]] (O₃), 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.

Oxygen is highly reactive, and in many other elements and compounds undergo [[exothermic reaction]]s with it (they [[combustion|burn]] or [[oxidization|rust]]).  If it were not for its continual replenishment as a waste product of plant [[photosynthesis]], the atmospheric oxygen would disappear, forming compounds with other chemicals at the earth's surface.

Oxygen is highly reactive, and in many other elements and compounds undergo [[exothermic reaction]]s with it (they [[combustion|burn]] or [[oxidization|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.

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]].  

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]].