Covalent Bonding and types of covalent structures + nanoparticles

what is covalent bonding?

a shared pair of electrons between two non metal atoms

what are polymers?

long chains made up of large repeating units called monomers

are polymers solid at room temperature?

yes as the molecules are really big, so the intermolecular forces add up to be quite strong, however most polymers melt easily as the intermolecular forces remain less strong than the chemical bonds

do covalent structures conduct electricity? explain your answer

no as they have no free electrons and they don’t have any charged particles( except graphite)

why do simple covalent structures have a low melting point?

because they have weak intermolecular forces so little energy is needed to overcome these

do giant covalent structures have intermolecular forces?

no as it’s just one giant molecule

why do giant covalent structures have high melting points?

because it takes a lot of energy to break all the strong covalent bonds between the atoms in the structure

what are allotropes?

different structural forms of the same element in the same physical state

what are the allotropes of carbon?

- diamond

- graphite

- graphene

- buckminsterfullerene

what is the structure of diamond?

each carbon atom is covalently bonded to 4 other carbon atoms

what are the properties of diamond?

- can’t conduct electricity as it has no free electrons or ions

- high melting point

- strong

what is the structure of graphite?

each carbon atom is covalently bonded to three others, the atoms are arranged in hexagons that form flat sheets that form layers on top of each other

what are the properties of graphite?

- slippery

- can conduct electricity

- high melting point

why is graphite slippery?

they have layers that are held together weakly as there are no covalent bonds between them so they can slide over each other making graphite soft and be used in pencil lead

why can graphite conduct electricity?

because each carbon atom is only bonded to three others, and carbon can make 4 covalent bonds, so there’s a carbon atom that isn’t bonded, so there’s a delocalised electron that can conduct electricity

what is graphene?

a singular layer of graphite

how are fullerenes such as nanotubes made?

made by bending sheets of graphene

what are fullerenes?

molecules of carbon with hollow shapes

what is buckminsterfullerene?

C₆₀ first fullerene to be discovered, spherical

uses of fullerenes

- industrial catalysts (spherical)

- transporting drugs into the body (spherical)

- electronics (cylindrical)

- strengthening materials eg. in tennis rackets

- lubricants (spherical)

what are the uses of nanoparticles

- silver nanoparticles have antibacterial properties so we can infuse them into surgical masks and wound dressings as they are lightweight as well

- catalysts due to their high surface area: volume ratio

- conducting electricity

- fullerenes to deliver drugs to the inside of cells

- sunscreens

what are the issues with using nanoparticles

- the use of nanoparticles is in ealry stages so we don’t know its long term effects on the human body ( if used in sunscreams for example)

- we don’t know if they damage the environment when they’re disposed of

- they aren’t easily disposed of