Chemical Bonding 4 Flashcards
State the difference between simple molecular structures and giant molecular structures.
Simple molecular structures consist of individual covalent molecules held together by weak attractive forces between the molecules known as intermolecular forces. Giant molecular structures consist of atoms that are held together by strong covalent bond that extend throughout the entire structure.
Name the 3 giant covalent molecules.
diamond, quartz / silicon dioxide (SiO2), graphite
Describe the structure of diamond.
Diamond is an allotrope of carbon. It has a giant molecular structure which consists of a 3D covalent network where each carbon atom is tetrahedrally bonded to 4 other carbon atoms, an arrangement that extends throughout the giant lattice.
Explain how the structure of diamond accounts for its high melting and boiling point.
A large amount of energy is required to break the strong and extensive covalent bonds between the carbon atoms throughout the giant lattice, hence the high melting and boiling points.
Explain why diamond is a non-conductor of electricity.
All the electrons are either held in the covalent bonds or held by the nuclei and are not free to move. Without mobile charge carriers, diamond is electrically neutral as no ions are present.
Explain why diamond is insoluble in all solvents.
Solvent molecules cannot penetrate the giant molecular lattice because of the strong covalent bonds between the carbon atoms and so, cannot solvate it, hence diamond is insoluble in all solvents.
Explain why diamond is very hard.
The structure of diamond is strong and rigid due to the strong and extensive covalent C-C bonds and the tetrahedral arrangement of the carbon atoms in a 3D network, preventing the carbon atoms from translational motion.
Describe the structure of SiO2.
SiO2 has a giant molecular structure, where each Si atom is covalently bonded to 4 O atoms, and each O atom is bonded to 2 Si atoms in a pattern that extends throughout the giant lattice.
List the properties of quartz, SiO2.
1: very high melting and boiling points
2: non-conductor of electricity
3: insoluble in all solvents
4: very hard
(all 4 properties of diamond apply to SiO2)
Define allotropes.
Allotropes are different forms of the same element, in which the atoms or molecules are arranged in different ways.
Identify 4 differences in terms of property between diamond and graphite.
1: Diamond is colourless and transparent, while graphite is black and opaque.
2: Diamond is very hard, while graphite is soft and slippery.
3: Diamond is an insulator of electricity, while graphite conducts electricity along the layers.
4: Diamond has a higher density (3.51g cm^-3) than graphite (2.27g cm^-3).
Describe the structure of graphite.
Graphite is an allotrope of carbon and has a giant molecular structure, with strong covalent bonds between each carbon atom within each layer and substantial dispersion forces between each layers.
Where are dispersion forces found in a graphite crystal?
A graphite crystal is composed of many layers of atoms. The interaction between each layer is dispersion forces.
List the properties of graphite.
1: Graphite has a high boiling and melting point.
2: Graphite is a good conductor of electricity.
3: Graphite is insoluble in all solvents.
4: Graphite is soft and slippery and has lubricating properties.
Explain how does the structure of graphite accounts for its high melting and boiling point.
A large amount of energy is required to break the strong covalent bonds between the carbon atoms within the layers in graphite, hence its high melting and boiling point.
