C3 - Structure and Bonding Flashcards
1
Q
Advantage and disadvantage of dot and cross diagrams
A
- Advantage - show us where the electrons come from
- Disadvantage - don’t tell use the shape of the compound
2
Q
Limitations of 2d stick model
A
- Doesn’t tell us which electron in the bond come from which atom
- Doesn’t show outer molecules not invloved in bonds
- Don’t give accurate shape
3
Q
Advantage and limitations of 3d stick model
A
- tell us the shape of the molecule
- Atoms aren’t joined by sticks in reality
4
Q
Advantages and disadvantages of ionic ball and stick diagrams
A
- Advantage - We can clearly see the ions in 3d
- Disadvantages - shows ions widely spaced when they are actually packed close together
- Give a mistaken impression of the size of lattices
- Assume ions are dense spheres
5
Q
Describe the structure and bonding of ionic compounds
A
- Non-metals gain electrons to form negative ions
- Metals lose electrons to form postive ions
- The bonds between the atoms are ionic bonds
- This froms a giant ionic lattice
- There are strong electrostatic forces of attraction between oppositely charged ions in all directions
6
Q
Properties of ionic compounds and why
A
- Very high melting and boiling points - strong electrostatic forces of attraction require lots of heat energy to overcome
- Cannot conduct electricity when solid - ions are locked in place by strong electrostatic forces of attraction
- Can conduct electricity when molten or in water - ions can now move and conduct electrical charge
7
Q
Describe bonding in metals
A
- Giant structure of positive ions arranged in layers
- Electrons are delocalised
- This sea of delocalised electrons can flow through the whole structure
- There is also a strong electrostatic attraction between the positive ions and the sea of delocalised electrons
8
Q
Properties of metals and why
A
- High metling and boiling points - strong electrostatic attraction requires lots of energy to overcome
- Excellent conductors of heat and electricity - delocalised electrons can move through structure and carry charge or thermal energy
- Malleable - layers of atoms can slide over each other
9
Q
What is an alloy and properties compared to pure metals
A
- An alloy is a mixture of 2 or more elements with at least 1 being a metal
- Different atom sizes distort the layers, meaning alloys are harder
- Delocalised electrons can’t flow as easily, meaning it isn’t as good of a conductor compared to pure metals
10
Q
Size of coarse particles and fine particles
A
- Coarse particles - between 1x10^-5 and 2.5x10^-6
- Fine particles - between 2.5x10^-6 and 1x10^-7
11
Q
Size of nanoparticles
A
- Diameter of 1-100nm
- only contain a few hundred atoms
12
Q
Advantages and disadvantages of nanoparticles
A
- LArge SA:V - much smaller quantity needed compared to normal particles of a catalyst so are cheaper and more efficient
- Can change the properties of the substance used
- So small that they still allow light through (transparent)
- Disadvantage - could be absorbed by body cells and long term effect is unknown
13
Q
USes of nanoparticles
A
- Suncream
- Medicines
- Cosmetics
- Deodorants
- Catalysts
14
Q
Structure of polymers and why are they solids at room temp
A
- Many repeating monomers in a chain joined by covalent bonds
- They are solid at room temperature due to strong intermolecular forces of attraction
- Some also have strong covalent crosslinks between chains
15
Q
Properties of small covalent molecules
A
- Low melting and boiling points - strong covalent bonds between atoms but weak intermolecular forces so little energy required to overcome them. They are liquid or gases at room temp
- Don’t conduct electricity - don’t have an overall charge and there are no free electrons to carry charge
