bonding topic (1st unit of year 10) Flashcards
ionic bond
positive and negative ions bonded together.
metallic bond
attraction of positive ions in a regular lattice and delocalised electrons.
covalent bond
when non- metals atoms bond together, they share a pair of electrons to make covalent bonds.
why do metals form +ve ions
they are losing electrons (the number of electrons lost depends on their group number) to make the outer shell)
why do non metals from -ve ions
they gain electrons to make a full outer shell (depending on their group number)
why do ionic substances have a high mpt
strong electrostatic forces of attraction between positive ions and negative ions that require a lot of energy to overcome.
one pair electron bond
single covalent
two pair electron bond
double covalent
what is a giant ionic lattice
lots of oppositely charged particles in a lattice structure with electrostatic forces of attraction that are strong and require a lot of energy to overcome as it has a high mpt. they are held together by ionic bonds
why do ionic substances have to be molten in order to conduct electricity
this is because if they are in a solid state they are not free to move meaning they cannot carry a charge and so they need to be moving in order to carry a charge and conduct electricity.
how do molecules form
through covalent bonding
how are simple covalent molecules held together
the atoms of the molecule are held together by strong covalent bonds however there are very weak intermolecular forces which do not require a lot of energy to overcome which means they have a low mpt and bpt.
how are giant covalent structures held together
made up of a huge number of atoms all joined by covalent bonds
why can giant covalent molecules not conduct electricity
this is because they do not carry a charge even when molten.
what is an electrostatic force
between oppositely charged particels
what are intermolecular forces
the forces between molecules
why cant simple covalent molecules not conduct electricity
this is because they do not have an overall electric charge.
how are giant molecular substances arranged
regular repeating lattices
why are giant covalent structures solid at room temperature
this is because they have millions of strong covalent bonds which means they have high mpt and bpt.
what is diamond formed from
carbon
how many covalent bonds does diamond form
4
why does diamond have a high mpt and bpt
because it has millions of carbon atoms joined by covalent bonds which require a lot of energy to overcome
why can diamond not conduct electricity
because it has no free electrons or ions .
how many covalent bonds does graphite from
3
what is the structure of graphite
sheets of carbon atoms arranged in layers
explain graphite’s structure
there are no covalent bonds between the layers they are only held together weakly, this means they are free to move over each other which makes them soft and slippery.
why has graphite got a high mpt
the covalent bonds in the layers need loads of energy to overcome.
explain why graphite is conductive
delocalised electrons between the layers which are free to move
when do ionic substances not conduct
when solid
what is the structure of graphene
a single layer of graphite and it is very thin
how many covalent bonds does graphene form
3
what is graphene’s use
touch screen
how many covalent bonds does nanotube form
3
how many covalent bonds does fullerene form
3
why does fullerene have a low mpt
weak intermolecular forces
what is the structure of a metal
positive ions in a lattice structure surrounded by delocalised electrons
why do metals have high mpt and bpt
this is because they have strong electrostatic forces between the positive ions and the delocalised electrons which results in strong metallic bonds that require a lot of energy to overcome.
why are metals conductive
they have delocalised electrons which are free to move and carry a charge.
explain why graphite is soft
because the layers of carbon slide over eachother
why are metals malleable
because the layers of atoms in a metal can slide over eachother
what do we do yo make pure metals stronger
mix them with other elements to make them harder
what do we do yo make pure metals stronger
mix them with other elements to make them harder
what happens when another element is mixed with a pure metal
the new atoms will distort the layers of the metal atoms making it more difficult for the layers to slide over each other.
how do you melt or boil a simple molecular substance.
break the intermolecular forces not the covalent bonds
what is the trend in mpt and bpt’s as a molecule gets bigger
increases as the intermolecular forces get stronger so it requires more energy to break them.
what is a covalent bond ?
between two atoms or ions in which the electron pairs are shared between them
