BONDING Flashcards
What is ionic compounds
Ionic compounds are oppositely charged ions and together by electrostatic attraction
Structures of ionic compounds
Most ionic compounds dissolve in water
Conduct electricity when molten
Have high melting points as there are many, strong electrostatic forces between oppositely charged ions lots of energy to overcome
What is covalent bonding
sharing a pair of outer electrons in order for to obtain a full shell
What is dative covalent bonding
are where one atom donates 2 electrons to an atom or ion to form a bond
Examples of giant covalent structures
graphite and diamond
Structure of graphite
layers slide easily as there weak forces between the layers
delocalised electrons between the layers allow graphite to conduct electricity as they can carry a charge
low density
insoluble as the covalent bonds are strong to break
high melting point as it has high lots of covalent bonds
Structure of diamond
tightly packed, rigid arrangement
very hard
very high melting points due to many strong covalent bonds
doesn’t conduct well as it doesn’t have any delocalised electrons
What is needed to work out shape of molecule
number of bond pairs and lone pairs
Why do molecules have a specific shape
Bonds repel each other equally . bonds contain electrons so they will want to be as far apart as possible
What do lone pairs do
push bonding pairs closer together
what shape does a bond pair 2 of and a lone pair 0 of have
linear 180 degrees
example is BeCl2
what shape does a bond pair 3 of and a lone pair 0 of have
Trigonal planar 120 degrees
example is BF3
what shape does a bond pair 4 of and a lone pair 0 of have
tetrahedral 109.5
example is CH4
what shape does a bond pair 5 of and a lone pair 0 of have
trigonal bipyramidal 90 120
example is PCl5
what shape does a bond pair 6 of and a lone pair 0 of have
octahedral 90
Example is SF6
what shape does a bond pair 3 of and a lone pair 1 of have
pyramidal 107
example is NH3
what shape does a bond pair 2 of and a lone pair 2 of have
bent 104.5
example is H20
what shape does a bond pair 3 of and a lone pair 2 of have
trigonal planar 120
example is ClF3
what shape does a bond pair 4 of and a lone pair 2 of have
square planar 90
example is XeF4
what is electronegativity
the ability for an atom to attract electrons toward itself in a covalent bond
what happens if there is a more electronegative element
pushes itself towards the more electronegative one
the bigger the difference in electronegativity
the more polar the bond will be
what are all the intermolecular forces in order from strongest to weakest
hydrogen bonding
permanent dipole dipole
van der Waals
when does van der waals exist
when 2 molecules or atoms are near by
The more van der waals forces
the bigger the molecule or atom
what happens when we boil a liquid
we are breaking the van der waals forces not covalent
where do permanent dipole dipole exist
in molecules with a polarity
what do PDD involve
molecules with a permanent dipole and so are stronger
what is hydrogen bonding
strongest intermolecular forces and occurs when you have very electronegative elements
molecules with h bonding also have
VDW and PDD
How are + ions formed
metals donate electrons to for a ‘sea’ of delocalised electrons . there is a n electrostatic attraction between + metal ions and - delocalised electrons . the more electron an atom can donate to the delocalised system the higher the melting points
structure of metals
good thermal conductors as the delocalised electrons can transfer kinetic energy
high melting point due to strong electrostatic force of attraction
metals insoluble as the bonding is too strong to break
good electrical conductors because the delocalised electrons can carry a current
