Bond+Types+and+Nomenclature

__**Bond Types and Nomenclature**__

There are two approaches to naming binary compounds (compounds made of two elements). There is one for ionic compounds and one for molecular ones. Using both methods, the name of the least electronegative is given first. The name of the more electronegative element follows. Ionic compounds are named according to the names of their component ions, including the charge of the cation (if it is variable). The compounds that are molecular are named using the prefixes listed in the table shown below to indicate the number of atoms of each type in the substance.


 * **Prefixes** || **Meaning** ||
 * Mono- || 1 ||
 * Di- || 2 ||
 * Tri- || 3 ||
 * Tetra- || 4 ||
 * Penta- || 5 ||
 * Hexa- || 6 ||
 * Hepta- || 7 ||
 * Octa- || 8 ||
 * Nona- || 9 ||
 * Deca- || 10 ||


 * Examples:**

||
 * //Ionic// ||  || //Molecular// ||   ||
 * MgH2 || magnesium hydride || OF2 || oxygen difluoride
 * FeF2 || iron (II) fluoride [[image:F2Fe1-7789288.jpg]]|| H2S || dihydrogen sulfide ||
 * Mn2O3 || manganese (III) oxide || Cl2O3 || dichlorine trioxide ||


 * __Exceptions__**

The division between the two methods is not always very clear. Both approaches can often be applied to the same substances. One example is TiO2. It is sometimes referred to as titanium (IV) oxide but is more commonly known as titanium dioxide.

__**Oxidation Numbers**__

The Roman numeral in the first name listed above is the oxidation number of the titanium. One reason for the overlap of the two methods lies in these numbers. Compounds of metals with higher oxidation numbers often behave as molecular compounds instead of ionic ones. One example is the case of SnCl4, which is called tin tetrachloride or tin (IV) chloride. This is a colorless liquid that freezes at -33ºC. However, ionic compounds are solids at room temperature. Because SnCl4 exhibits different properties from ionic compouds, we can say that compounds containing metals with high oxidation numbers often exhibit the properties of molecular compounds, not ionic ones.

__Sources__

The Book http://www.webelements.com/webelements/compounds/media/Fe/F3Fe1-7783508.jpg http://en.wikipedia.org/wiki/Image:Oxygen-difluoride-3D-vdW.png[|]