1.7.3Unit 1. Structure, Bonding and Introduction to Organic Chemistry
Carbon Allotropes — IAL Edexcel Linear (Chemistry) Revision Notes & Topical Questions
5 min read 5 parts Lesson 23 of 36 Unit quiz
Curriculum Equation Key معادلة تفاعل تكوين الإستر (الأسترة) - Esterification Reaction EquationFast Exam Solution
R-COOH + R2-OH ⇌ (conc. H₂SO₄) R-COO-R2 + H₂O
Word Equation & Conditions: حمض كربوكسيلي + كحول (في وجود حمض الكبريتيك المركز كعامل حفاز ونازع للماء) ⇌ إستر + ماء
Location & Specifications: الكيمياء العضوية للثانوية العامة والتحصيلي و Edexcel Chemistry.
Section 1 of 5Diamond and Graphite
Allotropes are different structural forms of the same element in the same physical state.
Diamond structure
- Diamond structure Each carbon atom forms four strong covalent bonds to others in a tetrahedral arrangement with 109.5° bond angles.
Diamond properties
- Diamond properties It is extremely hard, has a very high sublimation point, and does not conduct because no electrons are free to move.
Graphite structure
- Graphite structure Each carbon forms three bonds in flat hexagonal layers at 120°, leaving one outer electron per atom delocalised.
Graphite properties
- Graphite properties It conducts electricity along the layers and is soft and slippery because weak London forces allow layers to slide.
Section 2 of 5Graphene, Fullerenes and Nanotubes
Graphene, Fullerenes and Nanotubes
Graphene
- Graphene A single layer of graphite, one atom thick, which is very strong, transparent and an excellent conductor of electricity and heat.
Buckminsterfullerene
- Buckminsterfullerene C₆₀ is a hollow sphere of twenty hexagons and twelve pentagons, existing as separate simple molecules.
Properties of C₆₀
- Properties of C₆₀ Because it is simple molecular, it is soft, has a much lower sublimation temperature than graphite,
- and dissolves in some non-polar solvents.
Nanotubes
- Nanotubes Rolled-up sheets of graphene form cylinders with great tensile strength that can conduct electricity along their length.
Section 3 of 5Linking Structure to Properties
1
Identify the bonding in the structure: giant covalent for diamond and graphite, simple molecular for fullerenes.
2
For high melting points of diamond and graphite, say that many strong covalent bonds must be broken.
3
For conductivity, say whether any electrons are delocalised; graphite and graphene have them, diamond does not.
4
For softness of graphite, mention weak London forces between the layers, which allow them to slide over each other.
5
For lower melting points of fullerenes, point out that only weak intermolecular forces are overcome.
Section 4 of 5Uses
Uses
Diamond
- Diamond Used in cutting tools and drill bits because of its exceptional hardness.
Graphite
- Graphite Used as electrodes, as a lubricant and in pencils, because it conducts and its layers slide.
Graphene and nanotubes
- Graphene and nanotubes Used in developing lightweight composites and electronics because of their strength and conductivity.
Fullerenes
- Fullerenes Studied as carriers of drugs because the hollow cage can enclose other molecules.
| Allotrope | Bonds per carbon | Conducts? |
|---|---|---|
| Diamond | 4 | No |
| Graphite | 3 | Yes, along layers |
| C₆₀ | 3 | Very poorly |
Section 5 of 5Exam Checklist & Tips
1.7.3 – Key Points for the Exam
- Allotrope One of two or more different structural forms of an element in the same physical state.
- Giant covalent structure A lattice in which atoms are joined by covalent bonds throughout.
- Delocalised electron An electron that is not fixed to one atom and can move through a structure.
- Fullerene A hollow cage or tube of carbon atoms, such as C₆₀.
- Graphene A single layer of carbon atoms arranged in hexagons.
Common Mistakes
- Saying graphite conducts because it contains ions; it is delocalised electrons that move.
- Claiming diamond is hard because of strong bonds between layers, when it has no layers.
- Describing C₆₀ as a giant covalent lattice.
- Stating that London forces in graphite are broken when it melts;
- covalent bonds are also broken at its very high sublimation point.
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