Giant covalent structures

Question 1

What can covalent bonding lead to?

Answer 1

Small molecules
Giant lattices

Question 2

How do giant covalent lattices form

Answer 2

When a huge network of atoms bond covalently due to strong electrostatic attraction between the shared pair of electrons and nuclei

Question 3

Examples of giant covalent structures

Answer 3

Silicon
Silicon dioxide
Diamond
Graphite
Graphene

Question 4

What is the name of the shape diamond, silicon and silicon dioxide form?

Answer 4

A tetrahedron because the central atom is bonded to 4 other atoms which is repeated to form a tetrahedron shape

Question 5

What are the main properties of giant covalent structures?

Answer 5

Have high melting points
Extremely hard
Good thermal conductors
Insoluble
Can’t conduct electricity

Question 6

Why do giant covalent structures have high melting points?

Answer 6

Because a lot of energy is required to break the covalent bonds when melting

Question 7

Why are giant covalent structures extremely hard?

Answer 7

Because of the strong covalent bonds in the lattice arrangement

Question 8

Why are giant covalent structures good thermal conductors?

Answer 8

Because vibrations can easily travel through the stiff lattice thus conduct thermal energy

Question 9

Why are giant covalent structures insoluble?

Answer 9

Because the atoms are more attracted to neighbouring atoms in the lattice due to the electrostatic attraction (covalent bonds) than to the solvent molecules

Question 10

Why are giant covalent structures specifically insoluble in polar solvents?

Answer 10

Because they do not contain ions

Question 11

Why can’t giant covalent structures conduct electricity?

Answer 11

Because in many cases they do not contain charged ions or free electrons since all bonded electrons are held in localised covalent bond

Question 12

What giant covalent structure is an exception and can conduct electricity?

Answer 12

Graphite

Question 13

What is the structure of graphite?

Answer 13

Contains carbon sheets where each carbon shares 3 electrons with 3 other carbon atoms its bonded to, leaving the final electron to move free between sheets

Question 14

Why can graphite conduct electricity?

Answer 14

Because the free moving electrons which move between sheets can carry a charge

Question 15

Structure of graphene

Answer 15

A single layer of graphite:
Sheet of carbon atoms in hexagons where every carbon atom is bonded to 3 other carbons
And final electron moves along the sheet

Question 16

Properties of graphene

Answer 16

Conduct electricity: final electron moves along the sheet to carry charge
Transparent and light: one atom layer thick