bonding, structure and properties Flashcards
what is a compound?
substance in which two or more elements are chemically combined
what are the three types of chemical bonds?
- ionic
- covalent
- metallic
what is the bonding and structure like in iconic compound?
- bonding occurs between metals and non-metals
- electrostatic attractions between oppositely charged ions
- form a giant ionic lattice
- electrons are transferred [metals lose, non-metals gain]
what’s the diagram for ionic bonding?
[o]+ [o]-
what are the properties of an ionic compound?
- high melting and boiling points
- only conduct electricity when molten/dissolved
- brittle
what is the bonding and structure like in metallic compounds?
- giant structures of positive metal ions
- electrons in outer shell are delocalised [free to move through the whole structure]
- electrostatic attraction between positive metal ions and negative delocalised electrons
what are the properties of metallic compounds?
- layers can slide over each other, they can be bent [malleable and ductile]
- delocalised electrons so they can carry charge, can conduct electricity and heat
- bonds are very strong, high melting and boiling points
what is the bonding like in covalent bond?
- atoms share electrons
what’s the diagram for covalent bonding?
venn diagram thing
what are the properties of simple molecules?
- usually gasses or liquids that have low melting and boiling points
- weak intermolecular forces
- don’t conduct electricity
what are the properties of giant covalent structures?
- solids
- very high melting and boiling points
- strong covalent bonds
what are the properties of diamond?
- each carbon atom is covalently bonded to 4 other carbon atoms
- very hard
- very high melting point
- doesn’t conduct electricity
what is an allotrope?
different forms elements can exist in - the structures are made up of the same element, yet don’t have the same properties
what are the properties of graphite?
- each carbon atom is covalently bonded to 3 other carbon atoms
- layers of hexagonal rings with no covalent bonds between them
- layers can slide over each other, soft and slippery
- on electron from each carbon atom is delocalised
- can conduct electricity
what is graphene?
a single layer of graphite
what are fullerenes?
molecules of carbon atoms with hollow shapes, based on hexagonal rings of carbon atoms
what are carbon nanotubes?
cylindrical fullerenes with very high length to diameter rations
what can fullerenes be used for?
- lubricants
- to deliver drugs in the body
- catalysts
what can nanotubes be used for?
reinforcing materials eg. tennis rackets
milli, micro and nano?
- milli = (10^-3)
- micro = (10^-6)
- nano = (10^-9)
how many nano meters across are nanoparticles?
1-1000 nanometers
what are the uses of nano-silver?
it kills bacteria, so it’s used in wound dressings and deodorants
what are the uses of nano-titanium dioxide?
so small that they don’t reflect visible light and cannot be seen, so it’s used in sunblocks because they block harmful ultraviolet light
wha are the risks of nanoparticles?
- so small they could enter the bloodstream
- long-term effects aren’t known
- could enter and damage the environment
what are smart materials?
materials that are responsive to certain stimuli [temperature, light and moisture]
examples of smart materials:
- shape memory alloys/polymers -> can be bent and deformed but return to their original shape when heated
- thermochromic materials -> change colour when they reach a certain temperature
- photochromic pigments -> change colour when exposed to light
- polymer gels - >hydrogels absorb up yo 1000x their volume in water, changes in pH and temperature cause the water to be released
shape memory alloy uses:
inside car bodies and plates for bone fractures
shape memory polymer uses:
gum shields and medical stitches
thermochromic material uses:
mugs that change colour when their contents are hot
photochromic pigment uses:
sunglasses that darken when in bright sun
polymer gel uses:
nappies, fake snow and hair gel
