C2- Structure & bonding Flashcards
why do elements form bonds?
to get a full outer shell of electrons
state the three types of bonding
covalent, ionic and metallic bonding
describe covalent bonding
where non-metal atoms share pairs of electrons
describe ionic bonding
- where a metal atom loses electrons which are gained by a non-metal atom
- these oppositely charged ions are attracted to each other
describe metallic bonding
- where metal atoms lose electrons.
2. the positive metal ions are attracted to the delocalised electrons around them.
in covalent bonding, the number of bonds formed is always the…
same as the number of electrons needed for a full outer shell
covalent bonds can be…
(1) giant structures
(2) small molecules
why do giant structures have high melting/boiling points?
because lots of energy is needed to break the strong covalent bonds
why do small molecules have low melting/boiling points?
because not much energy is needed to break the weak intermolecular bonds between molecules
do covalent bonds conduct electricity? why?
No.
covalent bonds don’t have an overall electric charge (no mobile ions or electrons)
what are ions?
charged atoms or groups of atoms
how do atoms become ions?
by gaining/losing electrons
metal atoms lose electrons to…
form positive ions
non-metals gain electrons to…
form negative ions
why do giant ionic lattices have high melting/boiling points?
because lots of energy is needed to break the strong ionic bonds
what are the properties of ionic bonds?
- don’t conduct electricity as a solid
2. do conduct electricity when molten (liquid) or dissolved in water
why don’t ionic bonds conduct electricity when solid?
because the ions can’t move (immobile) so no charge can flow
why can ionic bonds conduct electricity when molten?
because the ions are mobile so a charge can flow throughout the structure
what are the strengths of using the dot & cross model?
- shows electrons gained/ lost
2. shows charge
state a weakness of using the dot & cross model
it doesn’t show lattice structure
what are the strengths of using a 2D model?
- partially shows the lattice structure
2. shows charge
state the weaknesses of using a 2D model
- doesn’t show electrons
2. hard to see 3D structure
what are the strengths of using the ball & stick model?
- shows lattice structure
2. shows charge
state the weaknesses of using the ball & stick model
- doesn’t show electrons gained/lost
2. gaps between ions are unrealistic
state 3 properties of metals
(1) high melting/ boiling points
(2) can be bent/ shaped
(3) can conduct electricity
why do metals have high melting/boiling points?
because lots of energy is needed to break the strong metallic bonds
why can metals be bent/shaped?
because the metal ions are in layers which can slide over each other
why can metals conduct electricity?
because they have delocalised electrons which can carry a charge throughout the structure
