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What are allotropes? Sketch the structure of two allotropes of carbon
Namely diamond and graphite. What is the impact of structure on
physical properties of two allotropes?
Answers
Answer:
The word allotrope refers to one or more physical forms of a chemical substance that exist in the same physical state. Allotropes can exhibit chemical and physical variations.
Diamond and Graphite, both are known as the allotropes of carbon. These minerals chemically consist of carbon atoms with different physical properties. These minerals, in general, are known to be as polymorphs, having the same type of chemistry, but of the various crystalline structures.
Diamond
It is the purest crystalline allotrope of carbon. It has a number of carbons, linked together tetrahedrally. Each tetrahedral unit consists of carbon bonded to four carbon atoms which are in turn bonded to other carbons. This gives rise to an allotrope of carbon having a three-dimensional arrangement of C-atoms. Each carbon is sp3 hybridized and forms covalent bonds with four other carbon atoms at the corners of the tetrahedral structure.
Graphite
Graphite is a pure form of carbon. This allotrope of carbon is composed of flat two dimensional layers of carbon atoms which are arranged hexagonally. It is a soft, black and slippery solid. This property of graphite persists because it cleaves easily between the layers.
In each layer, each C atom is linked to three C atoms via a C-C covalent bond. Each carbon here is sp2 hybridized. The fourth bond is formed as a pi bond. Since the π-electrons are delocalized, they are mobile and can conduct electricity.