Chemistry from Hydrogen to Tellurium - Carbon

Carbon


The sixth element on the periodic table is Carbon. By now you can probably guess how many electrons it has. Yes, you are right - it has 6. And its chemical symbol is C. 


Carbon is one of the most interesting elements known to scientists. It forms so many different compounds with other elements that there is a subdivision of chemistry called Organic Chemistry which is the study Carbon containing compounds. Organic chemists study the shape of Carbon containing molecules, their properties or traits, how to make them and their reactions with other chemicals.


The outer electron shell of Carbon has space for 8 electrons. Carbon has 2 electrons in its inner shell which leaves 4 in the outer shell. This means there are 4 spaces in the outer shell so each carbon atoms likes to bond or share electrons with 4 other atoms.

All of you will be familiar with Carbon and most of you use it every day. In recent weeks the elements we have been discussing don't exist on their own in nature and scientists have to extract them from other materials. Carbon is different. Carbon is a non-metal. Not only does it exist in nature, it can exist in different forms depending on how the atoms are arranged. 


In one form the Carbon molecules bond to 4 other Carbons with each atom as far from the next as possible. This gives a tetrahedral shape for 4 atoms and a 3 dimensional series of tetrahedra all joined together when there are lots of atoms. 

This form of Carbon is a clear, very hard crystal with lots of faces which reflect light and make it sparkle. We call this material Diamond.

The same Carbon molecules can also join together to form sheets of atoms. The atoms make a sheet of hexagonal rings and there are occasional links between 2 sheets to give a 3 dimensional structure. 

In this form Carbon is a black and very soft. We call this material Graphite. Graphite is used as the nibs or "lead" in pencils. Years ago real lead was used but it was found to be poisinous and was replaced by graphite. So the next time you write with pencil remember that you are rubbing layers of Carbon atoms from the nib onto your page!

Coal, soot and charcoal are also made from Carbon. In these cases the atoms are not arranged in such a regular structure 

 

In 1985 another allotrope or arrangement of Carbon atoms was discovered. It is similar to graphite but it consists of a combination of 5 and 6 atom rings. The 5 atom rings mean that the structure isn't flat so shapes like footballs and tubes can be formed. These are called Fullerenes.