Compounds of Carbon and Hydrogen - The Hydrocarbons

Consider methane, CH4, which is the simplest of the hydrocarbon compounds. It has the four electrons of the outer shell of carbon shared with one electron each from four hydrogen atoms. The electron shell of hydrogen is now full, and so stable, with two electrons - it has the helium outer electron structure. The carbon shell now has eight electrons in it, and so it is also full and stable. 

A pair of electrons can be represented by the straight lines shown between the carbon and the hydrogen. 

All of the Straight lines between the atoms represent pairs of electrons forming covalent overlap bonds which are called sigma ( r) bonds. All of the hydrocarbons mentioned so far are saturated molecules, meaning that there are no double bonds present in the molecule (see also Section 2.2.2). 

Single bonds (sigma bonds) will also be seen in the carbon-oxygen bonds discussed later in the alcohol series, where there is a C-O-H bond. Double bonds (sigma and pi bonds) also occur in aldehydes and ketones where there is a C==0 bond. These homologous series will be looked at in Module 7. 

Every ring has either the helium structure of two ciectrons or the stable octet of eight electrons 

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