Bonding Flashcards
Name the type of bond formed between N and Al in H3NaCl3 and explain how it is formed
Dative covalent bond and it is a shared pair of electrons where both come from the NH3
why is nitrogen oxide covalent
As there is a small electronegativity difference between them
So can’t be ionic
Of2 has a small electroneg difference so what type of crystal is it
Simple/ molecular
State the type of crystal structure shown by titanium
Its a metal so metallic structure. If ever unsure go with lattice would work for ionic and metallic if its covalent just write covalent
Why can titanium be hammered into objects with different shapes that can have similar strengths
As they (metals) have layers of atoms which can slide over each other meaning they are malleable
I) suggest why these objects have similar strengths
(Strong) (metallic) bonding re-formed / same (metallic) bonding / retains same (crystal) structure / same bond
strength / same attraction between protons and delocalised electrons as before being hammered
Fluorine reacts with bromine to form liquid bromine trifluoride what type of bonding is this and how is it formed
Covalent as 2 non metal, it is a shared pair of electrons one from br one from f
The melting point of sodium chloride is much higher than that of sodium metals, what can be deduced from this info
That the ionic bonding in nacl is greater and requires more energy to be broke than sodiums metallic bonding
Describe the bonding in a crystal of iodine (low mp) i2 and what crystal type is it
Van der waals forces
covalent and weak low mp
Its molecular
The heat energy needed to vaporise smth is much greater than the heat energy needed to melt it. Why
As to vaporise them all of the bonds must be broken
Predict the type of crystal structure of mgo which has a high mp
High mp so ionic
Why is graphite soft
As there are weak imf’s weak van der waal forces between the layers
State the meaning of the term electroneg
The atoms ability to withdraw a PAIR of electrons towards itself in A COVALENT BOND
State how two carbon-carbon atoms form a carbon-carbon bond in GRAPHANE
Shared pair of electrons, one from each atom
Explain why iodine vaporises when heated gently
As van der waals forces between molecules which are easily broken
Predict the shape of and the bond angle of the complex rhodium ion (RhCl4)2-
Tetrahedral 109.5
Which molecule does not have a permenant dipole. Ch3cl, chcl3, chcl2f or cf4
Cf4 doesn’t have one, low electroneg difference. and linear so dipoles cancel out
Which of these does not contain any delocalised electrons,
Polypropylene
Benzene
Graphite
Sodium
Polypropylene
Suggest one reason why electron pair repulsion theory cannot be used to predict the shape of a (Cocl4) 2- ion
As there are too many electrons in the orbitals. doesnt really work for electrons within the d orbital
What is the bonding in iodine
Covalent between atoms
Why is heat required to melt an iodine crystal
As bonds between molecules must be broken
What property of an atom causes it to be polar
Electronegativity.
Explain how the electron pair repulsion theory can be used to deduce the shape of the bond angle in PF3
P has 5 electrons in its outer shell, 3 from fluorine making a total of 8 electrons. There are 3 bond pairs and one lone pair. the electron pair repulsion theory states that electron pairs REPEL to be as far away as possible. Lone pairs repel more than bonded pairs, in conclusion forming a trig pyr shape with a bond angle of 107 degrees.
For a question comparing na nabr and naI what do you have to include
Talk about how na metallic bonds etc and THAT IS HAS A LATTICE STRUCTURE and nabr ionic stronger efoa stronger bonds opp ions and then how it is smaller than iodine so higher charger den BUT ALSO THAT NABR IS ALSO A LATTICE STRUCTURE
How are van der waals forces created
Movement of electrons in the fist molecule so all of the negative side, temporary dipole in this FIRST MOLECULE which induces another dipole in a NEIHBOURING MOLECULE and attraction of delta pos and delta neg.- difference in electroneg leads to bond polarity
Why is phosphine insoluble in water
As it does not form hydrogen bonds with water (weaker imfs so cant be surrounded by water molecules and vdws cant break hydrogen bonds to fit in w them)
Why is the melting point of I2 bigger than HI (6 marks)
I2 and HI are both molecular, intermolecular forces hold the molecule together. These are weak in both molecules so their melting points are both low. Iodine is a bigger mol than HI so it has more electrons so its vdw’s are stronger so more en needed ot break them so the mp is higher than HI eventhough they show permenant dipole dipole interactions the vdws in iodine are stronger though generally d-d would be stronger. So more energy is needed to break the imfs between the mols of iodine so its mp is higher.
Explain how the value of the cl-al-cl bond angle. In ALCL3 changes (if at all) the formation of the compound H3NAICl3 (baso nh3)
In alcl3 the bond is 120 degrees between all the bonds and when you add NH3 to it it becomes tetrahedral around the Al so the bond angle is now 109.5
what does adding cl do to water and why might it be a disadvantage
Kills bacteria, wasteful as most potable water isn’t used for drinking and some people might not like the taste
If we have CH3CL whats its shape
4 bonds so tetra but weird so distorted tetrahedral or just call it tetrahedral
Suggest a value for the H-O-O bond angles
94-105.5 degrees
An aluminium chloride molecule reacts with a chloride ion to form the AlCl4- ion. Name the type of bond formed in this reaction, explain how this type of bond is formed in the AlCl4- ion
Dative covalent and electron pair from cl- donated to Al(Cl3)
There are two lone pairs of electrons on the oxygen atom in a molecule of OF2 explain how the lone pairs of electrons on the oyxgen atom influence the bond angle in oxygen difluoride
Lone pairs repel more than bonding pairs bond angle will be lower than regular tetrahedral angle bond angle of 103-106 degrees
Explain why nickel is ductile
Has sheets of atoms which can slide over each other or layers of atoms or whatever
Ice- describe why melting point isnt that high but higih
Covalent bonds between atoms in water and hydrogen bonding exists between water molecules. Less energy is required to break hydrogen bonds in ice to form seperate water molecules
What is a ionic lattice
Regular repeating arrangement of oppositely charged ions
Explain why magnesium has a stronger mp than sodium
Magnesium has a higher nuclear charge so attracts delocalised electrons more strongly.
Describe lone pair bonded pairs for 2 2 bent
Lone pairs repel more than bonded pairs and will arrange themselves to be as far away as possible so the bond angle is REDUCED from 109.5 to 104.5 BASIcally its reduced from a tetrahedral w 4 bond pairs to 2 and 2
Why does distillation allow the separation of propanal from propanoic acid and propan-1-ol
As the aldehyde has dipole dipole forces whereas the alcohol and the carboxylic acid contain hydrogen bonds.
2 ways of maximising the yield of propanal by the reac mixtur
Keep the temp below 97 (as then the other two wont form, thats the boiling point of the second one and the third ones way higher at 146 so if the temps kept at below 97 the other ones wont seperate and you will max your yield of propanal
Also- by cooling the distillate. (Ensuring none is lost)
Suggest why graphene is an excellent conductor of electricity
Contains delocalised electrons which are able to move within the structure/crystal
Explain how vdw forces arise
Uneven distribution of charge causes a temp dipole in one molecule and this induces another temp dipole in a neighbouring mol
And there is an induced temporary attraction
explain how permenant dipole dipole forces arise between two molecules
differences in electronegativity leads to bond polarity
when does something not have perm dip dipo
if its linear or like b3f3 because they cancel out
why cant the vsepr theory be used for complex ions
bc only really works for s and p subshells, too many electrons in the d subshell
in terms of structure and bonding, explain why the boiling point of bromine is different from that of magnesium. suggest why magnesium is a liquid over a much greater temp range compared to bromine
bromine is molecular, mg is metallic. metallic bonds stronger. br has weak van der waals. mag has a much greater liquid range because the forces of attraction in liquids are stronger
explain how the value of the cl-al-cl bond angle in alcl3 changes if at all on the formation of the compound h3naIcl3
Aluminium is now surrounded by 4 electron pairs, is now tetrahedral. therefore the cl-al-cl bond would decrease from 120 degrees to 107-111 degrees in h3naIcl3
cyclohexene is prepared by the dehydration of cyclohexanol using conc phosphoric acid as a catalyst. identify the factors that influence the bps and state why cyclohexane can be seperated from the mixture o
cyclohexene= vdw forces cyclohexanol has h bonds. phosphoric acid has h bonds. cyclohexene has the weakest intermolecular forces so can be seperated by fractional distillation ias it should boil offf first
identify the condition that causes a bond in ccl4 to break
uv light and then the equation is ccl4–>ccl3 +cl radical
Explain, in terms of electronegativity, why the boiling point of H2S2 is lower than H2O2
Electronegativity of S lower than O
No hydrogen bonding between H2S2 molecules
Or only van der Waals
Suggest why the electronegativity of the elements increases from lithium to
fluorine.
as nuclear charge increases w similar shielding
Use the concept of electronegativity to justify why the acid strengths of ethanedioic
acid and ethanoic acid are different
ge 1: difference in structure of the two acids
• The acids are of the form RCOOH
• but in ethanoic acid R = CH3
• whilst in ethanedioic acid R = COOH
Stage 2: the inductive effect
• The unionised COOH group contains two very electronegative oxygen
atoms
• therefore has a negative inductive (electron withdrawing)effect
• The CH3 group has a positive inductive (electron pushing) effect
Stage 3: how the polarity of OH affects acid strength
• The O–H bond in the ethanedioic acid is more polarised / H becomes
more δ+
• More dissociation into H+
ions
• Ethanedioic acid is stronger than ethanoic acid
the melting point of XeF4 is higher than the melting point of PF3 . Explain why the melting points of these two compounds differ. give the shape of the molecule and explain why each molecule has that shape and how that shape infleuces the forces that affects the mp
XeF4 has 4 bps and 2 lps
Pf3 has 3bps and 1lp
xef4 is a square planar
pf3 is pyramidal
in pf3 electron pairs repel to be as far away as possible and lp repel even more than bps
xef4 has van der waals forces but pf3 has dipole dipole forces. the vdw in xef4 are stronger than dipole dipole in pf3 due to its larger mr. more electrons.
why would a longer mol have stronger vdws
more electrons, stronger van der waals BETWEEN MOLECULES
