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A '''compound''' is a [[molecule]] which is composed of more than one [[element]].   

A '''compound''' is a [[molecule]] which is composed of more than one [[element]].   

<ref>A compound is a substance with a fixed ratio of elements which determines the composition, and a particular organization which determines chemical properties. [http://www.newworldencyclopedia.org/entry/Chemical#Compounds New World Encyclopedia] </ref>

<ref>A compound is a substance with a fixed ratio of elements which determines the composition, and a particular organization which determines chemical properties. [http://www.newworldencyclopedia.org/entry/Chemical#Compounds New World Encyclopedia] </ref> Table salt, for example, is sodium chloride (NaCl), a compound composed of the elements sodium (Na) and chlorine (Cl) in a 1:1 ratio. Pure sodiun is a metal, and pure chlorine is a poisonous gas. When chemically combined, however, sodium and chlorine form an edible compound. This is a simple example of organized [[matter]] having emergent properties: A compound has characteristics different from those of its elements.[Reece, Jane B., and Neil A. Campbell. Campbell Biology / Jane B. Reece ... [et Al.].]</ref>  

Chemical compounds can be fairly simple, such as water (H₂O), which is just one [[oxygen]] atom and two [[hydrogen]] atoms.  Many are moderately complex, like sugars, which consist of no more than a few dozen [[carbon]], oxygen, and hydrogen atoms, e.g. C₆H₁₂O₆.  Some are relatively huge (still not visible to the naked eye), such as DNA, which can contain millions of atoms in one double helix crystal.  

Chemical compounds can be fairly simple, such as water (H₂O), which is just one [[oxygen]] atom and two [[hydrogen]] atoms.  Many are moderately complex, like sugars, which consist of no more than a few dozen [[carbon]], oxygen, and hydrogen atoms, e.g. C₆H₁₂O₆.  Some are relatively huge (still not visible to the naked eye), such as DNA, which can contain millions of atoms in one double helix crystal.