c3 Flashcards
bonding
How are covalent bonds formed?
by atoms sharing electrons
Which type of atoms form covalent bonds between them?
non-metals
Describe the structure and bonding of a giant covalent structure.
billions of atoms bonded together by strong covalent bonds
Describe the structure and bonding of small molecules.
small numbers of atoms group together into molecules with strong covalent bonds between the atoms and weak intermolecular forces between the molecules
Describe the bonding and structure of polymers.
many identical molecules joined together by strong covalent bonds in a long chain, with weak intermolecular forces between the chains
Why do giant covalent structures have high melting points?
it takes a lot of energy to break the strong covalent bonds between the atoms
Why do small molecules have low melting points?
only a small amount of energy is needed to break the weak intermolecular forces
Why do large molecules have higher melting and boiling points than smaller molecules?
the intermolecular forces are stronger in large molecules
Why do most covalent substances not conduct electricity?
do not have delocalised electrons or ions
Describe the structure and bonding in graphite.
each carbon atom is bonded to three others in hexagonal rings arranged in layers - it has delocalised electrons and weak forces between the layers
Why can graphite conduct electricity?
the delocalised electrons can move through the graphite
Explain why graphite is soft.
layers are not bonded so can slide over each other
What is graphene?
one layer of graphite
Give two properties of graphene.
strong, conducts electricity
What is a fullerene?
hollow cage of carbon atoms arranged as a sphere or tube
