Allotropes Of Carbon
Chapter Name : The P- Block Elements |
Sub Topic Code : 102_11_11_08_02 |
Topic Name : Allotropes Of Carbon |
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Sub Topic Name : Graphite |
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Introduction
• Graphite has a layered structure. • Layers are held by van der Waals forces and distance between two layers is 340 pm. • Each layer is composed of planar hexagonal rings of carbon atoms. • C—C bond length within the layer is 141.5 pm. • Each carbon atom in hexagonal ring undergoes sp2 hybridisation and makes three sigma bonds with three neighboring carbon atoms. • Fourth electron forms a ? bond. • The electrons are delocalized over the whole sheet. • Electrons are mobile and, therefore, graphite conducts electricity along the sheet. • Graphite cleaves easily between the layers and, therefore, it is very soft and slippery. E.g. in Pencils • For this reason graphite is used as a dry lubricant in machines running at high temperature, where oil cannot be used as a Lubricant. • Graphite is thermodynamically most stable allotrope of carbon
Pre-Requisites:
Elements, periodic table, allotrope
Activity:
Lead pencil is made up of the graphite. Due to its soft nature, graphite is used to make lead.
Real Life Question:
What is graphite used for?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| P block elements | Have the last electron in the outermost p orbital. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Pencil | The lead in the pencil is made of graphite. |
Real life uses :
• Graphite cleaves easily between the layers and, therefore, it is very soft and slippery. E.g. in Pencils • For this reason graphite is used as a dry lubricant in machines running at high temperature, where oil cannot be used as a Lubricant.
Places to visit :
Classroom.
Practical examples around us
| Examples | Explainations |
|---|---|
| Pencils | Lead in the pencil is made up of graphite. |
What you learn in Theory:
• Graphite has a layered structure. • Layers are held by van der Waals forces and distance between two layers is 340 pm. • Each layer is composed of planar hexagonal rings of carbon atoms. • C—C bond length within the layer is 141.5 pm. • Each carbon atom in hexagonal ring undergoes sp2 hybridisation and makes three sigma bonds with three neighboring carbon atoms. • Fourth electron forms a ? bond. • The electrons are delocalised over the whole sheet. • Electrons are mobile and, therefore, graphite conducts electricity along the sheet. • Graphite cleaves easily between the layers and, therefore, it is very soft and slippery. Eg in Pencils • For this reason graphite is used as a dry lubricant in machines running at high temperature, where oil cannot be used as a Lubricant.
What you learn in Practice:
• Graphite is thermodynamically most stable allotrope of carbon.