CIE iGCSE Co-ordinated Sciences-C2.6 Giant covalent structures- Study Notes- New Syllabus
CIE iGCSE Co-ordinated Sciences-C2.6 Giant covalent structures – Study Notes
CIE iGCSE Co-ordinated Sciences-C2.6 Giant covalent structures – Study Notes -CIE iGCSE Co-ordinated Sciences – per latest Syllabus.
Key Concepts:
Core
- Describe the giant covalent structures of graphite and diamond
Supplement
- Relate the structures and bonding of graphite and diamond to their uses, limited to:
(a) graphite as a lubricant and as an electrode
(b) diamond in cutting tools
CIE iGCSE Co-Ordinated Sciences-Concise Summary Notes- All Topics
Giant Covalent Structures of Graphite and Diamond
Giant covalent structures are made up of a large number of atoms held together by strong covalent bonds in a continuous three-dimensional network.
- Unlike simple molecular compounds, they do not consist of discrete molecules. The strong covalent bonds give these substances very high melting and boiling points.
Diamond
Diamond is composed entirely of carbon atoms.
- Each carbon atom forms four covalent bonds with other carbon atoms in a tetrahedral arrangement, creating a rigid three-dimensional lattice.
- Characteristics:
- Extremely hard due to strong covalent bonding in all directions.
- High melting point because all bonds must be broken to melt the structure.
- Does not conduct electricity as all electrons are involved in bonds.
Graphite
Graphite is also composed entirely of carbon atoms but arranged differently.
- Each carbon atom forms three covalent bonds with other carbon atoms, creating flat hexagonal layers.
- One electron from each carbon atom is delocalized and free to move within the layers.
- Weak van der Waals forces exist between layers, allowing them to slide over each other.
- Strong covalent bonds within layers give graphite a very high melting point, similar to diamond.
Example
Explain the structure of diamond in terms of covalent bonding and arrangement of carbon atoms.
▶️Answer/Explanation
Each carbon atom in diamond is bonded to four other carbon atoms in a tetrahedral lattice:
\( \text{Each C atom bonded to 4 C atoms} \)
This three-dimensional network makes diamond extremely hard and gives it a very high melting point. All electrons are held in bonds, so it does not conduct electricity.
Example
Describe the structure of graphite in terms of covalent bonding and arrangement of atoms.
▶️Answer/Explanation
Graphite consists of carbon atoms bonded to three others, forming flat hexagonal layers.
One electron from each carbon is delocalized and can move freely within the layers.
Layers are held together by weak van der Waals forces, allowing them to slide over each other. The strong covalent bonds within layers give graphite a high melting point.
\( \text{Each C atom bonded to 3 C atoms; 1 delocalized electron} \)
Uses of Diamond and Graphite Based on Structure and Bonding
The unique structures and bonding in diamond and graphite give rise to properties that determine their specific uses.
Diamond
Structure: Each carbon atom is covalently bonded to four others in a rigid three-dimensional tetrahedral network.
- Properties:
- Extremely hard due to strong covalent bonds in all directions.
- Use: Diamond is used in cutting tools, drills, and saw blades because its hardness allows it to cut through hard materials like glass and metals.
Example
Why is diamond used in cutting tools?
▶️Answer/Explanation
Diamond’s rigid tetrahedral lattice structure makes it the hardest natural material. This property allows it to be used in cutting and drilling tools that need to cut through very hard substances.
Graphite
Structure: Carbon atoms are arranged in flat hexagonal layers with one delocalized electron per carbon atom. Layers are held together by weak van der Waals forces.
- Properties:
- Soft and slippery – layers can slide over each other.
- Conducts electricity – delocalized electrons can move freely within layers.
- Uses:
- Lubricant – graphite’s layers slide easily, reducing friction between moving parts.
- Electrode – delocalized electrons allow graphite to conduct electricity.
Example
Why is graphite used as a lubricant?
▶️Answer/Explanation
The weak forces between graphite’s hexagonal layers allow them to slide over each other, making it an effective dry lubricant for machinery and locks.
Example
Why is graphite used as an electrode?
▶️Answer/Explanation
Graphite conducts electricity due to delocalized electrons within the layers, making it suitable for use as electrodes in electrolysis and batteries.