Forms of Carbon
Allotropy is the property of an element to exist in more than one physical forms having similar chemical properties but different physical properties.
Carbon exists both in crystalline and amorphous allotropic forms.
Crystalline allotropes of carbon:
Amorphous allotropes of carbon:
- Gas carbon
Crystalline allotropes of carbon
Diamond is a rigid, compact, three dimensional structure.
Diamond is very hard to break.
Diamond is bad conductor of heat and electricity. Because in diamond each carbon is bonded to four other carbon atoms. There are no free electrons present in it.
Diamonds are not attacked by acids, bases and other reagents but it can reacts with fluorine to form carbon tetrafluoride at about 1023 K temperature.
C + 2F2 → CF4
Diamond burns in air at about 1173 K to produce carbon dioxide gas.
In diamond carbon atoms are in tetrahedral arrangement.
Diamonds are used in glass cuttings and in making drills.
Diamond is widely valued in jewellary is used as an abrasive in sharpening tools.
Diamond is also useful in die-making and in the manufacture of tungsten filaments for light bulbs.
Because of reflection property it is used as gem injewellery.
Graphite contains carbon atoms in hexagonal rings, which are joined to form layers.
The layers of carbon can slide over each other. Graphite is a good conductor of heat and electricity. Since graphite contains free electrons, it is a good conductor of heat and electricity.
Graphite burns in air at about 973 K to produce carbon dioxide gas.
Since graphite is a good conductor of electricity it is used as electrode.
Graphite is used as moderator in nuclear reactors.
It is also used as solid lubricant in machines.
3. Fullerenes :
Fullerene was discovered in the year 1985.
C60 is the very popular and stable form of the known fullerenes. This consists of 60 carbon atoms arranged in pentagons and hexagons, like in a standard football.
Fullerenes are also called Buckminsterfullerenes as they are shaped like the geodesic dome designed and built by the US architect Buckminster fuller.
Fullerenes are prepared from graphite at higher temperatures.
There exists other members of fullerenes like C70, C84…etc