2. Bonding, structure and the properties of matter (covalent bonding and the structure and bonding of carbon) Flashcards
What is covalent bonding?
The sharing of electrons between non-metals
Why do non-metals gain electrons?
Because it is energetically unfavourable for them to lose electrons, so they gain electrons
What do covalent bonds form?
Covalent compounds
What 2 types of molecules can be formed as a result of covalent bonding?
- Simple covalent molecules
- Giant covalent structures/lattices
What are simple covalent molecules?
Molecules containing few atoms which are covalently bonded. Like H2, 02
What are examples of simple molecular covalent structures?
(H2, O2, Cl2, CH4)
What are the properties of simple molecular covalent substances?
- low melting and boiling points
- they are gases at room temperature
- cannot conduct electricty
Why do simple molecular substances have low melting and boiling points?
- The intermolecular forces between the molecules are very weak
- So not a lot of energy is required to overcome them
Why do simple covalent molecules not conduct electricity?
Because there are no free electrons or ions to carry charge
What are examples of giant covalent structures/lattices?
- Diamond
- Graphite
- Silicon dioxide
What does allotrope mean?
Different forms of something
What are the 3 giant covalent structures allotropes of?
Carbon
How many bonds can carbon atoms make in diamond?
4 bonds
What is diamond made up of?
Carbon atoms covalently bonded 4 times
What are the properties of diamond?
- High melting and boiling points due to incredibly strong covalent bonds
- Found as a solid
- Very rigid structure
- Does not conduct electricity because there are no free electrons or ions to carry charge
What is formed in graphite?
hexagonal structures
What does graphite have?
A free, delocalised electron
Why is graphite similar to metals?
Because it has a delocalised electron
What are the properties of graphite?
- High melting and boiling points because of the strong covalent bonds
- Can conduct electricity because of the free delocalised electrons
- It is arranged in layers of graphene that can be used as a lubricant, such as the lead in pencils
Why can graphite be used as a lubricant (such as, led in pencils)?
As the layers slide off of each other as it made up of layers that are one atom thick
What is graphene?
A single layer of graphite
Does graphene have the same properties as graphite?
Yes
What are fullerenes?
Carbon atoms arranged in hollow balls or closed tubes
What can fullerenes be used for?
- Drug delivery
- Catalysts due to huge surface area
- Lubricants
What can graphene be used for?
- Electronics
- Improving strength of composite materials
What is each grain of sand made out of?
Silicon dioxide
How many times is the carbon atom bonded in graphite?
3 times
What was the first fullerene to be discovered?
Buckminister fullerene (C60)
What shape does buckminister fullerene have?
a spherical shape
What is the structure of fullerenes?
hexagonal rings of carbon atoms
What are nanotubes?
- fullerenes which are tiny carbon cylinders
- they are good conductor of heat and electricity
What is this?
Nanotube
What is this?
Buckminsterfullerene
How do intermolecular forces change as the mass/size of the molecule increases?
- they increase, so melting and boiling points also increase
