Carbon and Its Significance
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8/12/2019 Carbon and Its Significance
Carbon and bonding
Carbonis classified as a non-metal. It is the first member of group IV of the periodic table and is located in period 2
between boron and nitrogen. The carbon atom has 6 electrons and therefore has an electron configuration is 2, 4.
This means it can either lose 4 electrons or gain 4 electrons to gain a stable electron configuration. It usually however
tends to covalent bond with other non-metals such as hydrogen and oxygen.
Since it has 4 valence (free) electrons, each carbon atom can be bonded with 4 hydrogen atoms, or 2 oxygen atoms.
Carbon atoms can therefore bind to form many compounds including hydrocarbons and carbohydrates. For this
reason it a useful base for the compounds of life. The large number of compounds is due to its ability to form bonds
with many elements, which can be single, double or triple bonds.
Carbon can from single bonds such as those in alkanes, double bonds such as those in alkenes, or triple bonds such as
those is present in alkynes. Carbon also bonds with itself to produce different allotropes.
Allotropes of carbon
Allotropesare forms of one element in the same physical state which have distinctly different physical properties i.e.
colour, density, hardness and electrical conductivity). Diamond and graphite are some of the allotropes of carbon.
Other elements which display allotropy are arsenic, phosphorus, selenium, sulfur, tin and oxygen. Allotropes have
different properties because the atoms are joined or packed together in different ways to form molecules or crystals.
Amorphous carbon (soot) is a low pressure form of carbon that usually exists in the form of as imperfect
tetrahedron structures. Each carbon is surrounded by 4 other carbons bonded to it with single bonds.
The carbon atoms in diamond are covalently bonded to four other carbon atoms to form a 3D covalent lattice,
with the shape around each carbon atom being tetrahedral. The 6 membered rings are buckled not flat.
All valence electrons are tied up in strong covalent bonds, so there are no mobile electrons. Thus it doesnt
It has an orderly arrangement of atoms throughout the whole crystal gives its transparency and brilliance. For this
reason it is used in jewellery.
Diamond is a hard substance because of the strong forces between molecules and it used therefore for drills and
Each carbon atom in graphite is bonded only to three other carbon atoms, forming a planar structure of flat
This leaves each carbon atom with 1 free valence electrons which forms a delocalised electron cloud located
between the layers (called aromaticity), similar to that present in metals.
These electrons are able to move within sheets. As a result, graphite is able to conduct electricity. However, it can
cause a temporary dipole in one sheet which by electrical induction will cause a dipole of the opposite charge to
occur in a neighbouring sheet. For these reasons, it is used for the electrodes in dry cell batteries and
In graphite, weak intermolecular forces between layers are present, resulting in these layers being able to readily
sheer off or to slide over one another. For these reasons, it is used for pencils, and also as a dry lubricant.
Graphite lubrication abilities are hypothesised to be due to the presence of a fluid layer (i.e. air) between the layers
(as graphite is a poor lubricant in a vacuum).
8/12/2019 Carbon and Its Significance
Other allotropes of carbon
Electrical discharge between graphite electrodes in low pressure helium causes graphite to evaporate and then
condense as soot. If soluble in benzene or toluene, it forms a yellow-brown substance with 60 carbon atoms that
has a soccer ball structure.
Buckminsterfullerenes(bucky-balls) are 5-6 membered rings that combine to form a spherical cage. The most
common has 60 carbon atoms. Other fullerenes with 70, 74 and 80 carbon atoms have also been produced. In fact,
the number of carbon atoms can range from 32 to 84 carbon atoms. Bucky-balls have some delocalised electrons but not like graphite.
Cage-like fullerenes may have uses as superconductors or as lubricants because of the weak intermolecular forces
between their ball-shaped molecules. However since they are expensive to produce, other materials are used
Nanotubes(or bucky-tubes) are other group of fullerenes consist of molecules that have tube-like shape, that are
several nanometres long.
Nanotubes have high tensile strength, and can act as either conductors or insulators