FC11: Structure & Bonding Flashcards
Describe the bonding in metallic substances
metallic bonding - electrostatic attraction between the positive metal ions and delocalised negative electrons
What is the structure of metallic substances
giant metallic lattice
What does the strength of a metallic bond depend on
the number of delocalised electrons per atom
What is the trend in melting point in metals
as the number of delocalised electrons per atom increases, melting point increases, as more energy is needed to break the stronger metallic bonding
What substances have simple molecular structure
covalent substances that do not have a giant covalent lattice structure
what is the bonding in simple molecular substances
covalent
what is the trend in melting points in simple molecular substances
As the total number of electrons increases, the strength of london forces between molecules increases, and so more energy is required to overcome the intermolecular forces, and so melting point increases as total number of electrons increases
What is the bond or forces in simple molecular substances
intermolecular forces: hydrogen bonding, pd-d forces, london forces
what substances have giant covalent structures
diamond, graphite, graphene, silicon, silica, boron
what is the structure of diamond (describe no. of bonds around carbon atoms and shape)
4 covalent bonds around each carbon atom, tetrahedral shape
what is the structure of graphite (describe no. of bonds around carbon atoms and shape)
3 covalent bonds around each carbon atom, trigonal planar shape
how can graphite conduct electricity but not diamond
graphite has one delocalised mobile electron per atom, which can flow between the layers to carry a charge, whereas diamond cannot as all 4 of its outer electrons are involved in bonding
explain the high electrical conductivity of graphite and graphene in relation to their structure, and also the strength of the structure
trigonal planar shape around each carbon atom, 3 covalent bonds per carbon therefore 1 electron remains unused, creating a sea of delocalised electrons giving them a high electrical conductivity. London forces holds the layers together which are weak (pencil)
Describe the mpt/bpt of giant covalent substances
many strong covalent bonds which require a lot of energy to break, and so giant covalent substances have high melting and boiling points
describe the bonding in substances with a giant ionic lattice structure
ionic bonding - electrostatic attraction between oppositely charged ions
describe the mpt/bpt of giant ionic compounds
very high mpt/bpt, as a lot of energy is needed to break many strong ionic bonds
explain the electrical conductivity of ionic compounds
cannot conduct electricity as solids, because there are no mobile charge carriers.
can conduct when molten or dissolved in aqueous solution as there are mobile ions and therefore can carry a charge
explain the solubility of ionic compounds in water
soluble in water, ions can form strong attractions to water molecules, sometimes so strong that they can remove ions away from the giant ionic lattice structure and form hydrated ions. Forming ion-dipole bonds (force between an ion and water molecules
what is a hydrated ion
ion surrounded by water molecules
ion surrounded by water molecules
hydrated ion
explain the relationship between graphene and graphite
graphene = one singular layer of carbon atoms
graphite = multiple layers of carbon atoms
what properties of graphene mean that it is likely to have important technological applications
very high tensile strength, very good electrical conductor
