is found in many different compounds. It is in the food you eat, the clothes you
wear, the cosmetics you use and the gasoline that fuels your car. Carbon is the
sixth most abundant element in the universe. In addition, carbon is a very special
element because it plays a dominant role in the chemistry of life. Carbon, discovered
in prehistory and was known to the ancients, who manufactured it by burning organic
material making charcoal. There are four known allotopes of cabon: amorphous,
graphite, diamond and fullerene. A new (fifth) allotrope of carbon was recently
found. It is a spongy solid that is extremely lightweight and, unusually, attracted
to magnets. The inventors of this new form of carbon -- a magnetic carbon nanofoam--
say it could may someday find medical applications (see review
article from Nature)
Physical Properties of the Carbon Atom
Number 6 Atomic Mass Average: 12.011 Melting Point: 3823 K (3550°C
or 6422°F) Boiling Point: 4098 K (3825°C or 6917°F) Density:
2.267g/cu.cm. Velocity of sound [/m s-1]: 18350 Hardness Scale Mohs:
0.5 Stable Isomers (2)
Carbon atom has six electrons, 4 of the electrons are in its valence shell (outershell).
The circles in the diagram show energy levels - representing increasing distances
from the nucleus.
diagram is, however, a simplification and can be misleading. It gives the impression
that the electrons are circling the nucleus in orbits like planets around the
sun. Actually it is not possible to know exactly where the electrons are located
A better way to look at the carbon atom is by using an energy level graph
shown at the right. Here we see carbon has six electrons represented by arrows
(the direction of the arrow represents the electron spin) Two electrons are found
in the 1s orbital close to the nucleus. The next two will go into the 2s orbital.
The remaining ones will be in two separate 2p orbitals. This is because the p
orbitals have the same energy and the electrons would rather be in separate orbitals.
The actual location of electrons in a carbon atom cannot be determined
with certainty and the electrons appear to be 'smeared' into orbitals as shown
below. These images were created using the java applet --Atomic and Molecular
Orbitals from MIT. This java applet and other Molecular Orbitals applets can be
found at the Chemistry Java Page.
Isotopes are atoms which have the
same atomic number but different mass numbers. They have the same number of protons
but different numbers of neutrons.The number of neutrons in an atom can vary within
small limits. For example, there are three kinds of carbon atom 12C, 13C and 14C.
They all have the same number of protons, but the number of neutrons varies.
types of carbon atoms are called isotopes. The fact that they have varying numbers
of neutrons makes no difference to the chemical reactions of the carbon atom.
Uses of Carbon
Graphite combined with clays form the 'lead'
used in pencils. Diamond is used for decorative purposes, and also as drill
bits. Carbon added to iron makes steel. Carbon is used for control rods
in nuclear reactors. Graphite carbon in a powdered, caked form is used as
charcoal for cooking, artwork and other uses. Charcoal pills are used in
medicine in pill or powder form to adsorb toxins or poisons from the digestive