2.1 - Bonding, structure and properties Flashcards
How do you find out the group number and period number of an element from its electronic structure?
Group number = number of electrons in the outer shell
Period number = number of shells
What is an isotope?
An element that has the same number of protons but different number of neutrons
What does ionic bonding occur between?
Metals and non-metals
What is the attraction between ionic compounds? And what is it?
Electro static attraction.
Attraction between opposite charges/ions
What are the properties of a giant ionic lattice?
-high melting point b/c strong electro static forces between ions need lots of energy to break
-soluble b/c ionic lattice disociates in water
-electrical conductivity (only when molten or dissolved) b/c ions are free to move about
What does covalent bonding happen between? Are ions formed?
non-metals only
no ions formed
What are the common molecules that contain double bonds?
Oxygen (O2), Carbon Dioxide (CO2), Carbon Sulphide
What is the difference between intermolecular bonds and intramolecular bonds?
Intermolecular bonds are between molecules and are weak
Intramolecular bonds are within molecules and are strong
What are the physical properties of simple covalent compounds?
-low melting/boiling point b/c intermolecular bonds and so don’t need lots of energy to break.
-don’t conduct electricity as no free electrons to move and carry charge
What are two examples of Giant Covalent structures?
Diamonds and Graphite
What are the properties of a Diamond?
- Hard b/c strong covalent bonds
- high melting point b/c strong covalent bonds
- no free electrons to conduct electricity
How many intramolecular bonds do each carbon atoms form?
4 strong intramolecular covalent bonds
What are the uses of a Diamond?
drill bits because they have a high melting point
What are the properties of Graphite?
- Soft/slippery b/c weak intermolecular forces between layers
2.high melting points b/c lots of strong covalent bonds
3.conducts electricity b/c delocalised electrons
How many intramolecular bonds does each carbon atom have?
3 strong intramolecular covalent bonds
The fourth electron is found delocalised between the layers
Carbon can also form fullerenes. What is an example of a fullerene?
Buckminster fullerenes (buckyballs)
What are the uses of bucky balls?
Drug delivery, lubricants, as catalysts and in nanotubes
What are carbon nanotubes?
A type of fullerene
What are the properties of nanotubes?
- among the stiffest and strongest fibres
- very strong b/c covalently bonded and free electrons give a high electrical conductivity
What is graphene?
is similar to just one layer of the graphite molecule
What are the properties of graphene?
- thinnest material known to man
- lightest material known to man
- strongest material known to man
- best conductor of electricity
How is metallic bonding held together?
held together by electrostatic forces between delocalised electrons
What are the properties of metallic bonding and why?
- high melting/ boiling points as strong electrostatic forces of attraction between positive metal ions and delocalised electrons
- conducts electricty as delocalised electrons free to move
- malleable as has regular structure and deloclised electrons which makes it easier for metal ions to slide over each other
- high density as closely packed structure
What is the scale in a nanostructure?
1-100nm or 1x10 -9
Silver is a nanomaterial. What does it do?
It kills bacteria (doctors use wound dressings containing silver to treat ext infections)
Titanium dioxide is a nanomaterial. What does it do?
It absorbs and reflects harmful UV rays from the sun
Butyl rubber is a nanomaterial. What does it do?
It slows down the escape of air so balls don’t lose air quickly
Zinc oxide is a nanomaterial. What does it do?
It absorbs and reflects harmful UV rays from the sun
What is the definition of a smart material?
Smart materials have properties that change reversibly with a change in their environment.
State the properties of thermochromatic pigments and their uses.
They change colour with changing temperature.
Mugs that change colour
State the properties of photochromatic pigments and their uses.
They change colour with changing light intensity
Holiday T-shirt designs
State the properties of hydrogels and their uses.
They absorb/expel water and shrink/swell due to changes in pH or temp
Baby nappies
State the properties of shape memory alloys and their uses.
Metals which regain their original shape when heated
Kettle springs
State the properties of shape memory polymers and their uses.
Plastics which regain their original shape when heated
Gum shields
