c3 structure and bonding Flashcards
covalent bonding
atoms can share or transfer electrons to form strong chemical bonds a covalent bond is when electrons are shared between non metal atoms the number of atoms depends on how many extra electrons ann atom needs to make a full outer shell if you include electrons that are shared between atoms each atom has a full outer shell
single bond=each atom shares one pair of electrons
double bond=each atom shares two pairs of electrons
ions
atoms can lose electrons to give them a full outer shell the number of protons is then different from the number of electrons the resulting particle has a charge and is called an ion
ions conductivity
solid ionic substances do not conduct electricity because the ions are in fixed positions and not free to carry charge when melted or dissolved in water ionic substances do conduct electricity because the ions are free to move and carry charge
ions melting points
ionic substances have high melting points because tje electrostatic force of attraction between oppositely charged ions is strong and so requires lots of energy to break
ionic bonding
when metal atoms react with non metal atoms they transfer electrons to the non metal atom metal atoms lose electrons to become positive ions non metal atoms gain electrons to become negative ions
giant ionic latice
when metal atoms transfer electrons to non metal atoms you end up with positive and negative ions these are attracted to each other by strong electrostatic force of attraction the electrostatic force of attraction works in all directioins so many billions of ions can be bonded together in a 3d structure
giant covalent structure
many billions of atoms each one with a strong covalent bond to a number of others a example is diamond they have high melting and boiling points because the strong covalent bonds between the atoms must be broken to melt or boil the substances this requires a lot of energy
small molecules structure
each molecule contains only a few atoms with strong covalent bonds between these atoms different molecules are held together by weak intermolecular forces water is a example it has low melting and boiling points because only the intermolecular forces need to be overcome to melt or boil the substances not the bonds between the atoms this does not require a lot of energy
large molecules structure
many repeating units joined by covalent bonds to form a chain the small section is bonded to many identical sections to have the left and the right seperate chains are held together by inter moleculer forces that are stronger in small molecules polymers are examples their meltig and boiling points are low compared to giant covalent structures but higher then for small molecules they require a lot of enery to break and are normally solids at room temperature
graphite
is a giant covalent structre but is different to the other giant covalent substances
structure of graphite
made only of carbon each carbon atom bonds to three others and forms hexagonal rings in layers each carbon atom has 1 spare electron which is delocalised and therefore free to move around the structure
hardness of graphite
the layers can slide over each other because they are not covalently binded graphite is therefore softer then diamond even thought both are only of carbon as each atom in diamond has 4 strong covalent bonds
conductivity of graphite
the delocalised electrons are free to move through graphite so can carry charges and allow an electrical current to flow graphite is therefore a conductor of electricity
fullerenes
hollow cages of carbon atoms bonded together in one molecule can be arranged as a sphere or a tube called a nanotube molecules held together by weak intermolecular forces so can slide over each other can conduct electricity
fullerene spheres
backminster fullerene was the first fullerene to be discovered and has 60 carbon atoms other fullerenes exist with different numbers of carbon atoms arranged in rings that form hollow shapes fullerenes like this can be used as kubricants for drug delivery
