Covalent bonding Flashcards
(18 cards)
How are covalent bonds formed?
By atoms sharing electrons.
Which types of atoms form covalent bonds between them?
Non-metals.
Describe the structure and bonding of a giant covalent substance.
Billions of atoms are 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 inter-molecular forces between the molecules.
Describe the structure and bonding of polymers.
Many identical molecules joined together by strong covalent bonds in a long chain, with weak inter-molecular forces between the chains.
Why do giant covalent substances 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 inter-molecular forces.
Why do large molecules have higher melting and boiling points than small molecules?
The inter-molecular forces are stronger in large molecules.
Why do most covalent substances not conduct electricity?
They 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 layer.
Why can graphite conduct electricity?
The delocalised electrons can move through the graphite and carry charge.
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 .
It is strong and conducts electricity.
What is a fullurene?
A hollow cage of carbon atoms arranged as a sphere or tube.
What is a nanotube?
A hollow cylinder of carbon atoms.
Give two properties of nanotubes.
It has high tensile strength and conducts electricity.
Give three uses of fullurenes.
Lubricants, drug delivery (spheres) and high tech electronics.
