Covalent Bonding Flashcards
What is a covalent bond?
When electrons are shared between non-metal atoms
What happens in a single bond?
Each atoms shares a pair of electrons
What happens in a covalent double bond?
Each atom shares two pairs of electrons
How many atoms are shared?
It depends on how many electrons are needed to make a full outer shell
What is a giant covalent structure?
Many billions of atoms each with a strong covalent bond to a number of other atoms.
What is an example of a giant covalent structure?
Diamond
What are small molecules?
A fixed and limited number of atoms which are held tightly together by strong covalent bonds.
What is an example of a substance made of small molecules?
Water
What are large molecules?
Many repeating units joined by covalent bonds to form a chain.
What is an example of a large molecule?
Polymers
Why do most covalent structures not conduct electricity?
They do not have delocalised electrons that are free to carry a charge throughout.
Name 2 properties of giant covalent bonds.
High melting and boiling points, solid at room temperature, strong covalent bonds between atoms
Name 2 properties of small molecules.
Low melting and boiling points, gaseous or liquid at room temperature, weak intermolecular forces
In giant covalent bonds, what needs to be broken for a substance to be melted or boiled?
Covalent bonds between the atoms -> requires lots of energy
In small molecules, what needs to be broken for a substance to be melted or boiled
Intermolecular forces -> does not require a lot of energy
Name 2 properties of large molecules.
Melting and boiling points lower than giant covalent but higher than small molecule, stronger intermolecular forces, usually solid at room temperature
What is graphite?
A type of giant covalent structure - different to other giant covalent substances
What is the structure of graphite?
Made of only carbon.
Each carbon bonds to three other carbons.
Forms hexagonal rings in layers.
In graphite, what does each carbon have?
One spare delocalised electron
Why can the layers slide over each other in graphite? What does this mean?
Not covalently bonded. It is therefore softer than diamond.
In diamond, what does each carbon have?
Four strong covalent bonds - each atom bonded to 3 others
How is graphite unique?
It is one of the only covalent structures to conduct electricity as its atoms have delocalised electrons.
What is graphene?
A single layer of graphite.
What is a fullerene?
Hollow cages of carbons covalently bonded together in one molecule.
What is a nanotube?
A fullerene rearranged into a tube structure.
What are the intermolecular forces like in fullerenes?
Weak intermolecular forces -> molecules can slide over each other
Can fullerenes conduct electricity?
Yes.
What is buckminsterfullerene?
A type of fullerene with 60 carbon atoms - the first fullerene discovered
What is the structure of buckminsterfullerene?
Sphere
What is a use of fullerenes like buckminsterfullerene? (carbon atoms arranged in rings that form hollow shapes)
Lubricants, drug delivery
What is a property of nanotubes?
High tensile strength (difficult to break when pulled)
Give a use of nanotubes.
In electronics
