2.2.8 Structures of Covalent Compounds Flashcards
Which two structures can compounds with covalent bonds have?
Simple molecular lattice or giant covalent lattice.
What are simple molecular structures made up from?
Small, simple molecules.
What bonds are there in simple molecular structures?
The atoms within each molecule are held together by strong covalent bonds. The different molecules are held together by weak intermolecular forces (such as van der Waals’ or London forces).
Why do simple molecular structures have low melting and boiling points?
The intermolecular forces are weak, so a relatively small amount of energy is needed to break them.
Why are simple molecular structures non-conductors of electricity?
There are no charged particles free to move.
Why are simple molecular substances generally soluble in non-polar solvents, such as hexane?
Weak London forces are able to form between covalent molecules and these solvents. This helps the molecular lattice to break down and the substance dissolves.
Why do giant covalent structures have high melting and boiling points?
High temperatures are needed to break the strong covalent bonds within the lattice.
Why are giant covalent structures generally non-conductors of electricity?
There are no free charged particles.
Which giant covalent lattice can conduct electricity?
Graphite because delocalised electrons between the layers are able to move freely, parallel to the layers, when a voltage is applied.
Why are giant covalent structures insoluble in both polar and non-polar substances?
The covalent bonds are too strong to be broken.
