Hydrocarbons multiple covalent bonds

Saturated hydrocarbon A hydrocarbon containing no multiple covalent bonds, with each carbon atom bonded to four other atoms. 

Unsaturated hydrocarbon A hydrocarbon containing at least one multiple covalent bond. 

Carbon can form multiple bonds (double or triple bonds see Ch. 1) between its atoms when forming compounds. This can be shown in some simple hydrocarbons (see Fig. 2.2). In covalent bonds, the sharing of a pair of electrons comprising one electron from each atom involved in the bond is called a single bond and is represented by a single line. The bond is formed by two electrons for example, in ethane, C2H6 ... 

In transition metal oxides, multiple oxidation states and the propensity for covalent bonding affect both the bulk and surface structures. The change of oxidation state of the anions typically gives these materials a range of possible compositions and is also the basis of much of the catalysis in which they are involved. One example for which there are published calculations is vanadium pentoxide, V2O5. Vanadia-based compounds are used as catalysts for the oxidation of hydrocarbons and other organic molecules under mild conditions and also find application as NOx reduction catalysts by selective reduction with NH3. 

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