Tutorial 2.2 - Covalent Bonding and Structure

Question 1

Explain why graphene conducts electricity but diamond does not. [4]

Answer 1

• both are giant covalent
• graphene (because each C is bonded to only 3 other Cs) it has delocalised free electrons which can move and carry charge
• diamond does not have this

Question 2

difference between bonds between molecules and between atoms in simple molecular and giant covalent

Answer 2

simple molecular - bond between MOLECULES
giant covalent - bonds between ATOMS

???check later but learn anyway??/

Question 3

Explain why carbon dioxide sublimes at —79 °C but silicon dioxide boils at 2950 °C. [6]

Answer 3

• both substances have covalent bonds
• but CO2 is simple molecular
• so it has weaker forces of attraction between molecules
• so less energy required to break them
• whereas SiO2 is giant covalent
• so stronger attractions between atoms
• and more energy required to break them

Question 4

displayed formula of SiO2

Answer 4

same as CO2 - does have double bonds