What do diamond wedding rings, sketching pencils, cotton t-shirts, and energy drinks have in common? They are all made primarily of carbon. Carbon is one of life’s most fundamental elements. For example, it makes up 18.5 percent of the human body by mass - we find it in places such as our muscle cells, bloodstream, and in the conductive sheaths surrounding our neurons. These compounds generally consist of carbon bonded to other elements such as hydrogen, and you’ll explore them more in Organic Chemistry. However, we can also find structures made just from carbon. Examples of these include diamond and graphite.
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Jetzt kostenlos anmeldenWhat do diamond wedding rings, sketching pencils, cotton t-shirts, and energy drinks have in common? They are all made primarily of carbon. Carbon is one of life’s most fundamental elements. For example, it makes up 18.5 percent of the human body by mass - we find it in places such as our muscle cells, bloodstream, and in the conductive sheaths surrounding our neurons. These compounds generally consist of carbon bonded to other elements such as hydrogen, and you’ll explore them more in Organic Chemistry. However, we can also find structures made just from carbon. Examples of these include diamond and graphite.
Carbon structures are structures made up of the element carbon.
These structures are all known as carbon allotropes.
An allotrope is one of two or more different forms of the same element.
Although allotropes may share the same chemical composition, they have very different structures and properties, which we’ll look at in just a second. But for now, let’s look at the way carbon forms bonds.
Carbon is a non-metal with an atomic number of 6, meaning it has six protons and six electrons. It has the electron configuration \(1s^22s^22p^2\) . If you aren’t sure what this means, check out Electron Configuration and Electron Shells for further information.
Ignoring sub-shells, we can see in the image below that carbon has four electrons in its outer shell, also known as its valence shell.
This means that carbon can form up to four covalent bonds with other atoms. If you remember from Covalent Bond, a covalent bond is a shared pair of electrons. In fact, carbon is rarely found with anything other than four bonds because forming four covalent bonds means it has eight valence electrons. This gives it the electron configuration of a noble gas with a full outer shell, which is a stable arrangement.
These four covalent bonds can be between carbon and almost any other element, be it another carbon atom, an alcohol group (-OH) or nitrogen. However, in this article we are concerned with the various structures it forms when it bonds with other carbon atoms to make different allotropes. We refer to all these different allotropes as carbon structures. They include diamond and graphite. Let’s explore them both further.
Diamond is a macromolecule made entirely of carbon.
A macromolecule is a very large molecule made up of hundreds of atoms covalently bonded together.
In diamond, each carbon atom forms four single covalent bonds with the other carbon atoms surrounding it, resulting in a giant lattice stretching in all directions.
A lattice is a regular repeating arrangement of atoms, ions or molecules. In this context, 'giant' means it contains a large but indeterminate number of atoms.
You should remember that covalent bonds are extremely strong. Because of this, diamond has certain properties.
Graphite is also an allotrope of carbon. Remember that allotropes are different forms of the same element, so like diamond, it is made up of just carbon atoms. However, each carbon atom in graphite forms just three covalent bonds with other carbon atoms. This creates a trigonal planar arrangement as predicted by electron pair repulsion theory, which you’ll learn more about in Shapes of Molecules. The angle between each bond is .
The carbon atoms form a 2D hexagonal layer almost like a sheet of paper. When stacked up, there are no covalent bonds between layers, simply weak intermolecular forces.
However, each carbon atom still has one remaining electron. This electron moves into a region above and below the carbon atom, merging with the electrons from the other carbon atoms in the same layer. All these electrons can move anywhere within this region, although they can’t move between layers. We say that the electrons are delocalised. It is much like the sea of delocalisation in a metal (see Metallic Bonding).
Graphite’s unique structure gives it some different physical characteristics to diamond. Its properties include:
A single sheet of graphite is called graphene. It is the thinnest material ever isolated - it is just one atom thick. Graphene has similar properties to graphite. For example, it is a great conductor of electricity. However, it is also low density, flexible and extremely strong for its mass. In the future you might find wearable electronics made from graphene embedded in your clothing. We currently use it for drug delivery and solar panels.
Although diamond and graphite have many similarities, they also have their differences. The following table summarises this information.
Carbon has six proton, six neutrons and six electrons.
Carbon dioxide consists of a carbon atom joined to two oxygen atoms with covalent double bonds. It has the structure O=C=O.
Carbon dioxide consists of a carbon atom joined to two oxygen atoms with covalent double bonds. It has the structure O=C=O.
What is an allotrope?
One of two or more forms of the same element.
State the maximum number of bonds a carbon atom can form.
4
Define macromolecule.
A large molecule made up of hundreds of atoms covalently bonded together.
Define lattice.
A repeating regular arrangement of atoms, ions, or molecules.
Describe the structure of a diamond macromolecule.
Give the molecular formula for diamond.
C
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