Why Is Carbon So Important?

What does a diamond ring and a lead pencil have in common?...

Answer: they are both made of carbon. (We will explain how shortly)..

Useful web resource:

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Introductory_Biology_(CK-12)/01%3A_Introduction_to_Biology/1.09%3A_Significance_of_Carbon

Carbon is element number 6. What makes this element so special compared to the rest of the elements?

Carbon is the element of life. When we talk about organic chemistry, we are talking about compounds and substances containing carbon.

Without carbon, life as we know it would not be the same. Without it, there would be no carbohydrates, no proteins, no lipids and no nucleic acids- all of which contain carbon. Without these, there would be no cells that make up our bodies and no DNA to carry our genetic information.

So, why is carbon so special? Why can it produce all of these important materials? This is due to how carbon reacts..

Carbon is element no 6 - it has an atomic number of 6. This means it has 6 electrons and 6 protons. The first 2 electrons fill carbon`s inner electron shell, with 4 electrons in the second shell. As such, carbon atoms can form 4 covalent bonds with other atoms to gain a full shell of outer electrons. This allows it to bond with lots of different elements including hydrogen (to form hydrocarbons) and other carbon atoms (to form carbon allotropes).

So, what do we mean by carbon allotropes?

Carbon allotropes are different forms that carbon can exist in as a pure element - ie molecules made up of only carbon atoms with no other elements.

This includes diamond, graphite, graphene, carbon nanotubes, and buckminsterfullerene

Take a look at this web link to see the different structures of these allotropes:

https://www.researchgate.net/figure/Carbon-allotropes-Graphite-3D-Graphene-2D-CNT-1D-Fullerene-0D-and-Diamond_fig3_324099198

Essentially, each structure contains carbon atoms only bonded together in slightly different ways to produce different structures with quite dramatically different properties.

We`ll take each allotrope in turn to look at its structure and its properties:

Diamond`s structure

Diamond has a giant covalent structure with 1 carbon atom covalently bonded to 4 other carbon atoms in a regular lattice arrangement. There are no free electrons in this structure.

Diamond`s properties

Rigid &structure means diamond is very hard. Can be used for cutting tools. No free electrons means it does not conduct electricity.

Graphite`s structure

Graphite has a giant covalent structure with 1 carbon atom covalently bonded to 3 carbon atoms. The carbon atoms form layers with a hexagonal arrangement of carbon atoms. These layers have weak forces between them. Each carbon atom has 1 free, delocalised electron.

Graphite`s properties

Layers in graphite can slide over each other due to weak forces between the layers - this makes graphite slippery and it therefore can be used as a lubricant and in lead pencil (think of how soft a lead pencil is to use). Free delocalised electrons in graphite means it is a good conductor of electricity. So it can be used for electrodes in batteries and in electrolysis reactions.

Graphene`s structure

Graphene is essentially a single layer of graphite. Graphene has a large regular arrangement of carbon atoms - 1 carbon atom is covalently bonded to 3 carbon atoms. It has no layers with weak forces in between as in graphite, only 1 layer with strong carbon-carbon covalent bonds.

Graphene`s properties

As it only has strong bonds between its carbon atoms and is made of a single layer, graphene is not slippery like graphite. It is very hard. In fact, graphene is believed to be the strongest material yet discovered, some 200 times stronger than steel! Remarkably, it is this strong with a high tensile strength too - meaning it can be stretched significantly before breaking. Due to its strong bonds, it has a very high melting point. Like graphite, it is good conductor of electricity well due to its delocalised electrons.

Uses of graphene are likely to increase in the future due to its mixture of properties - strength, high tensile strength, lightweight, good conductor of electricity. The problem is it is difficult to obtain on a large scale - more and more research is being done into the best way to harness graphene on a larger scale. It`s current and potential uses include: composite materials in cars/planes etc, construction materials, lubricants, electronics, batteries and more.

Finally, fullerenes are carbon allotropes with hollow shapes - either ring (nanotube) or ball (buckminsterfullerene) structures...

Carbon nanotube structure

Carbon nanotubes are a type of fullerene which resembles a layer of graphene (1 carbon atom covalently bonded to 3 carbon atoms) but rolled into a tube/cylinder shape. They also have delocalised electrons.

Carbon nanotube properties

Like graphene, nanotubes are strong with a high tensile strength and high melting point. They are good conductors of electricity. Due to their hollow structure, they can be used in drug delivery. Their high tensile strength makes them useful in the production of tennis racquets.

Buckminsterfullerene structure

Another fullerene material, this type of carbon structure has a ball/sphere structure - hence named buckyballs. Its chemical formula is C60 - again each carbon atom covalently bonds with 3 other carbon atoms, with its structure composed of 60 carbon atoms bound together. They are made of large molecules but do not have a giant covalent structure (there is not an indefinite number of carbon atoms bound together). Weak intermolecular forces exist between individual buckyballs. There are delocalised electrons but they cannot move from one buckyball molecule to another.

Buckminsterfullerene properties

The weak intermolecular forces between each buckyball mean buckminsterfullerene has a lower melting point than graphite or diamond. It is also slippery. It is a poor conductor of electricity as although there are delocalised electrons they cannot move between each buckyball molecule as there are no bonds between adjacent buckyballs. There are potential uses in medicine and as lubricants.

So we`ve covered a lot on the different compounds containing carbon (organic compounds) as well as the different structural forms carbon can exist in (its allotropes). Hopefully you can see how unique and amazing carbon is and that you can now explain what the diamond in a ring and the lead in a pencil have in common!