Electrostatic attraction between oppositely charged ions
How are ionic bonds draw?
as lewis diagrams showing outer shell e- and the ion charges.
What determines ionic bond strength?
- Charge on Ion- higher charge = stronger attraction
- Ionic radius- larger radius= a weaker attraction.
Physical properties of giant ionic structures.(4)
- Have high mp/bp
- solid at RT
- many are soluble in water, none are soluble in oil
- conduct in solution or molten but not when solid.
What is a giant lattic and draw one?
A giant lattice is when lots of cations and anions form into a reguar 3d lattic that can extend in anydirection.
What is the conductivity of a ionic structure like?
cant conduct as a solid becuase the ions are fixed in a ridgid lattic and cannot move to create a current.
In a solution/molten the cations and anions are free to move and can create a flow of charged particles meaning it conducts.
electrostatic attraction between cations and a sea of delocalised electrons.
Properties of metalically bonded compounds.(3)
conducts as a solid and molten
maleable and ductile
Bond strength in meatlic bonding
In group 1 - up to 1e- can be delocalised = weak bond- low mp and soft
Same is true for group 2 and 3
ionic radis also effects it- larger= less attraction= weaker.
cation charge- higer=more attraction
Draw a metalic bond.
why are metals ductile and malleable
The non directional bonds allow layers to more easily slip past each other which allows deformation.
What happenes when you alloy a metal?
the new metal ion replaces a old metal ion.
this prevents layser slipping past each other from occuring as easily which makes the metal harder etc.
electrostatic attraction between two neucli and the same shared pain of e-
dative covAlEnt bond(co ordinate bond):
covAlEnt bond formed when one atom donates both e-
why is diamond strong?
- Giant covelant structure
- Each carbon bonned very strongly to four other carbons, formins a tertrahedral arraangement with bond angle 109.5
Properites of graphite
- Giant covalent structure
- Made of very strong 2d hexagonal layers
- with a sea of deloclised ei in between that allows conductions and the layers to slip.
what is the valence shell electron repuslsion theory
e- in the outer shell travel to be as far apart as possible due to their repulsion.
Lone pairs repel more (as they are closer )
double bonds act as a single bond.
What shape and bont angle forms with 2 bonding pairs out of 2 electron pairs eg BeCl2
What shape and bont angle forms with 3 bonding pairs out of 3 electron pairs eg AlCl3
What shape and bont angle forms with 4 bonding pairs out of 4 electron pairs eg CH4
What shape and bont angle forms with 3 bonding pairs out of 4 electron pairs eg NH3
What shape and bont angle forms with 2 bonding pairs out of 4 electron pairs eg H2O
bent , v-shaped , non-linear
What shape and bont angle forms with 6 bonding pairs out of 6 electron pairs eg SF6
What shape and bont angle forms with 5 bonding pairs out of 5 electron pairs eg PF5
90 degrees and 120 degrees
five steps of detemining shape.
- Group number of central atom
- add one for each bond
- Add 1 for each -ve charge, subtract 1 for each +ve
- add up and divide by 2
- detrimin number of bonding and lone pairs and state shape
SHape of CO2
Linear as it has 2 double bonds .
what is the octet rule?
atoms react to gain a full outer shell of 8 e-
draw sulfur dioxide .(odd)
Bond angle 120 degrees , bent
the abilty of an atom to attract e- towards intself in a bond.
How does electronegativity change across the periodic table?
top right (fluorine) is the highest, bottom left is the lowest. most the noble gasses dont have a EN becuase they dont form bonds
General rule for En and bond type.
ΔEn>2 then predict ionic
ΔEn<1 then predict non polar covalent
What does a molecule need to have a permanent dipole?
assymetry and polar bonds.
why does En increase across a period and up a group?
Across a period- shielding e- stays the same but neuclear charge increase which increases attraction (atomic radius also increases attraction)
Down a group shielding e- and charge increase at the sma erate and cancel out, but atomic radius increases which decreases the attraction.
What is van der waals' interaction?
its exists in all molecules, its a temporary dipole caused by a temporary asymmetry in e- arrangement due to the e- moving arond the shells/oribitals..
a temp dipole iduses more temp dipoles in other molecules.
this means molecules are attracted to each other by these temp dipoles.
What effects size of van der waals' attraction?
number of e- - as this means theirs a greater chance of assymetry in e- arrangement , and the temp dipole could be stronger.
What is a hydrogen bond
not a bond - its a intermolecular force.
the strongest intermolecular force
What two properties does a hydrogen bond require?
- Contains a O-H , N-H , or H-F bond
- lone pair on the O, N or F on a neighbouring molecule.
Draw a hydrogen bond and what are the 3 key points .
- Straght line across the drawing
- Show dipoles and lone pairs
- lable hydrogen bond between lone pair and Hδ+
Whats the general rule for solubility?
like disolves like
eq polar disolves polar and vice versa
Why can ionic molecules disolve in water?
The ions gets completly surrounded by water molecules
a dipole to ion attraction will form and allow mixing
Why cant non-polar organic componds disolve ions?
ion- van der waals' attraction is very weak so they dont mix.
why does etanol dissolve in water?
ethanol contains a O-H and can therefore hydrogen bond with the water.
Why do non polar molecules mix with each other?
as both only have van der waals' as their stongest attracting they are attracted to the other compound equally and will mix.
What are the 3 annolymous properties of water.
- density of solid is less then density of liquid
- Has an unusually high surface tension
- has an unusually high mp/bp compared with other simple covalent molecules.
Why is water denser as a liquid than a solid?
As a liquid water forms and breaks hydrogen bonds all the time, as it cools it has too little energy to overcome the hydrogen bonds. This means that each H2O molecule gets held in an open lattice with space inbetween the molecules, which makes it less dense.
Why has water got a high surface tension?
a network of hydrogen bonds forms. This means that when a force is applied to the water it gets distributed outwards across more water molecules.
WHy has water got an unusually high mp/bp?
each water molecule can form up to 4 hydrogen bonds creating an extensive network of hydrongen bonding. THiese intermolecular forses require more energy to over comewhich means water has a higher bp/mp then other simple covalent molecules.
Key points when answering a question on bonding and structure.
- Say how its bonded and which intermolecular forses it has(compare with othe rmolecules)
- what does that bonding tell u about tis conductivity, solubilty ,bp etc and why
- what shape is the simple covelant molecule say i predict.
- what need to break/ be overcome when it boils.
Whats a better rule then the octet rule?
unpaired e- pair up(expansion of the octet)