AQA GCSE chemistry topic 2 - bonding, structure and properties of matter
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60 Terms
what are the three types of bonding ?
ionic, covalent and metallic.
what does ionic bonding occur between?
metals + non-metals.
what does covalent bonds occur between?
non-metal + non-metal
what does metallic bonding occur between?
metal + metal
what happens to the electrons during ionic bonding?
they are transferred
what happens to the electrons during covalent bonding?
they are shared
what happens to the electrons during metallic bonding?
they become delocalised.
how do atoms become ions?
by gaining or loosing an electron
what happens when you loose a negative electron?
it becomes more positive
what happens when you gain a negative electron?
it becomes more negative.
what looses electrons?
what gains electrons
what is the definition of ionic bonding ?
ionic bonding is the strong electrostatic attraction between two oppositely charged ions.
what do ionic compounds form?
giant ionic lattices
what are the three properties of giant ionic lattices?
they’re arranged in a regular repeating structure, each ion is surrounded by ions of the opposite charge, the electrostatic attraction acts in all different directions.
what are the properties of ionic compounds?
high melting and boiling points, SOLID ionic compounds DON’T conduct electricity, LIQUID AND AQUEOUS ionic compounds DO conduct electricity.
why do ionic compounds have high melting and boiling points?
because a large amount of energy is required to overcome the strong electrostatic forces.
why do ions need to move?
to make electricity flow.
what is the definition of a covalent bond?
the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.
what do some covalent substances consist of?
small molecules
what are the two types of forces?
inside a molecule - strong covalent bonds.
between molecules - weak intermolecular forces.
what happens when a molecular substance melts/boils ?
you overcome the intermolecular forces.
why do small molecules have a low melting / boiling point ?
only a small amount of energy is needed to overcome the intermolecular forces.
why don’t intermolecular forces conduct electricity?
there are no free-moving ions.
what is a polymer?
many repeating units joined together.
what is a giant covalent structure?
a massive network of atoms joined by covalent bonds.
what is diamond made from?
carbon - each carbon atom forms 4 covalent bonds with 4 other carbon atoms.
what are the properties of diamond?
very high melting point
its extremely hard
it doesn’t conduct electricity.
why don’t diamonds conduct electricity?
they use all four outer electrons to make covalent bonds so there are no delocalised electrons.
what is graphite made of ?
carbon - each carbon atom forms 3 covalent bonds with 3 other carbon atoms.
why can the layers slide over one another?
there are no covalent bonds between the layers
what are the properties of graphite?
very high melting point
its soft
it does conduct electricity
why is graphite soft?
there are no covalent bonds between the layers.
why does graphite conduct electricity?
there is one electron per carbon atom that is delocalised.
is silicon dioxide a giant covalent bond?
yes
what are the properties of silicon dioxide?
very high melting point
solid at room temperature
doesn’t conduct electricity
why doesn’t silicon dioxide conduct electricity?
there are no free - moving electrons.
what is the definition for metallic bonding ?
strong electrostatic attraction between positive metal ions and delocalised electrons.
what is a giant metallic structure?
metal ions are arranged in a regular pattern.
what are the properties of metals?
can conduct electricity
can conduct heat
can be bent
why can metals conduct electricity ?
because they have delocalised electrons that can move through the structure and carry electrical charge.
why can metals conduct heat?
the delocalised electrons can also carry energy.
why can pure metal be bent?
the atoms are arranged in layers that can slide over each other.
why do we make alloys ?
pure metals can be too soft for many uses.
what is an alloy?
a mixture containing a metal and one or more other element.
why are alloys harder than pure metals?
they have different sized atoms to distort the regular layers.
what happens when a substance melts?
energy is transferred to the substance
the particles gain energy
they vibrate/move more
eventually the forces holding the particles in their fixed positions are overcome enough for them to move around each other.
what are the limitations of the particle model?
particles aren’t solid spheres
there are forces between particles
it doesn’t fully represent the complexity of a real particle.
what are nanoparticles ?
extremely small particles
how big is a nanoparticle ?
between 1-100nm
how big is a nanometer (nm)
0.000000001m
why are nanoparticles useful?
they have a very high surface area : volume ratio
why are there risks of nanoparticles?
because they are so small.
what is graphene?
one single layer of graphite.
what are the properties of graphene?
very high strength
electrical conductivity
a very thin structure
what are fullerenes?
made of entirely carbon and they have hollow shapes.
name one example of a fullerene
buckminsterfullerene - C₆₀
what are carbon nanotubes?
cylindrical fullerenes
what do carbon nanotubes have?
a very high length : diameter ratio
what are carbon nanotubes useful for?
nanotechnology
electronics
materials