are very hard and the graphite of the pencil's tip is very soft. These
two different substances contain a wonderful proof of creation called
carbon.
A rough, unpolished diamond is the hardest of all minerals. (1) For
this reason, a crystal diamond is used to cut and to drill all kinds
of material and is also used as an abrasive tosmooth surfaces. (2)
Hardness is the resistance of a mineral to scratches from outside
forces; it is easy to recognize mineralsby this trait. By scratching
one mineral with another, their relative hardness canbe determined.
Scientists use a point system to designate the hardness of all
minerals. They rate diamonds with the highest ratio of ten over ten.
So, what makes diamonds so hard?
It is very interesting that the soft, breakable graphite in a pencil
tip is made up of the same atoms as a diamond. Graphite is composed of
the same carbon atoms as a diamond. But, while one is very soft, the
other is extremely hard. One is as black as a lump of charcoal; the
other may besparkling bright. One is commonly found in nature; the
other is rare. For all these reasons, diamonds are much more valuable
than graphite. How is it then, that carbonatoms can be so different
from one another?
Carbon: The Foundation of Life
(The Value of Diamonds is Determined by its Atoms)
Before we consider the differences, we must speak about the carbon
atoms that make up a diamond. The carbon atom is very important
forliving creatures. Nevil Sidgwick, the English chemist, states the
following in his book, Chemical Elements and Their Compounds :
Carbon is unique among the elements in the number and variety of the
compounds which it can form. Over a quarter of a million have already
been isolated and described, butthis gives a very imperfect idea of
its powers, since it is the basis of all forms of living matter. (3)
The class of compounds formed exclusively from carbon and hydrogen are
called hydrocarbons. This is a huge family of compounds that include
natural gas, liquid petroleum, kerosene, and lubricating oils. The
hydrocarbons ethylene and propylene form the basis of the
petrochemical industry. Hydrocarbons like benzene, toluene, and
turpentine are familiar to anyone who has worked with paints. The
naphthalene that protects our clothes from moths is another
hydrocarbon. Hydrocarbons combined with chlorine or fluorine form
anesthetics, which are the chemicals used in fire extinguishers and
the Freon used in refrigeration.
As one can see, carbon is very important; it is what makes the diamond
a rare mineral. A diamond has norival for being the finest example of
a crystalline structure in the world. Thecarbon atoms that give the
diamond crystal its hardness have an ideal geometric design.
Graphiteis also formed from carbonbut its atoms are not ordered as in
a diamond. Scientists describe this difference by the world allotropy
.
The Concept of Allotropy
The difference, in the arrangement of space, in the atoms that make up
the structure of an element is called allotropy . The atoms that
produce the structure are called allotrope atoms. We can explain this
with the following example:
Imagine that we have bought three loads of 10,000 bricks each and that
all these brinks are identical to one another. We have sent these
brinks to three different bricklayers who will each build a wall to
their own design independently of the others.
-Would the walls be identical?
-Would they all have the same sturdiness?
-Would the artistic arrangement of the bricks be similar?
If the answer to these questions is yes, the wall will not be allotropic.
If the answer to these questions is no, we can call the walls allotropic.
Oxygen and ozone are allotropes of oxygen atoms.
Diamonds, graphite, and amorph carbon are allotropes of carbon atoms.
White phosphorus and redphosphorus are allotropes of phosphorus atoms.
Rhombic sulfur and monocline sulfur are allotropes of sulfur.
Characteristics of Allotrope Atoms:
- The atom and its atomic number are the same.
- Their molecular geometry is different.
- They have different inclinations to enter chemical reactions, but
thecompounds formed by such a reaction are the same.
- The molecular sturdiness is different.
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