Readings Flashcards
what is sp3 hybridisation?
when the s orbital hybridises with all three p orbitals to form tetrahedral shapes
what shape is made through sp2 hybridisation?
trigonal planes are made
sigma bond:
sp2 orbitals merging together nicely in-line with the nuclei
what is a sp3 orbital a blend of?
sp3 = a blend of one s orbital and three p orbitals
what is an sp2 orbital a blend of?
sp2 = a blend of one s orbital and two p orbitals
what is an sp orbital a blend of?
sp orbital = blend of one s and one p orbital
what shape is an s orbital?
sphere
what does an orbital simply tell you?
the most probably location in which you can find an electron
how many types of p orbital are there?
3 types: one in the x-axis (px), on the y-axis (py) and one in the z-axis (plz)
what are degenerate orbitals?
degenerate orbitals are orbitals with the same energy
what governs the energy of hybrid orbitals?
the energy of a hybridised orbital will be dependant upon the proportion of s:p orbitals within the hybrid orbital - for example if it is sp3 it will be 75% closer to the energy of a p orbital than it is to 25% of an s orbital
hybrid orbitals are fused to form which type of bond?
sigma bonds (o with a quiff)
what are π bonds always made from?
π bonds are always made from unhybrisised p orbitals. (when you’re dealing with carbon atoms)
what is the difference between a pie bond and a sigma bond?
sigma bonds are made from hybridised orbitals whilst pie bonds are made from unhybridised orbitals
every double bond has at least:
one sigma and one pie bond
every carbon single bond has:
at least one sigma bond
every carbon triple bond has at least:
one sigma bonds and two pie bonds
what bonds is stronger than the other between sigma and pie bonds?
sigma bonds are stronger than pie bonds
every single bond in a organic molecule contains at least:
one sigma bond
every double bond in a organic molecule contains at least:
one sigma and one pie bond
what essentially is hybridisation:
when different atomic orbitals of same or nearly same energy combine together to form new hybrid orbitals
all hybrid orbitals have the same energy, they are referred to as being…
degenerate
unhybrid orbitals form:
pi bonds
hybrid orbitals form:
sigma bonds
what essentially is the span of sp-sp3 orbitals describing?
the sp-sp3 orbitals essentially describe how electrons from different sub-orbitals come together in bonds to form differing types of hybrid orbitals (e.g. count all the electrons present in bonds, determine what proportion are in s:p, these ration values allow you to determine what sp-sp3 it is and there for the structure as each sp hybrid has its own structure)
word to describe the energy of degenerate orbitals which have energy in between the two set p & s values:
intermediate energies
what happens to the spherical s orbitals and two-lobed p orbitals once hybridisation takes place?
once hybridisation takes place, both the original orbitals cease to exist and together the hybrid forms an entirely new orbital pattern
what happens to the shape of electron clouds when hybridisation takes place?
they form into their distinct shapes that are characteristic of their hybridisation types (e.g. sp3 = tetrahedral (4 lobes equally apart from one another))
pi bond comes from:
the overlap of unhybridised p orbitals
WHERE do sigma and pi bonds form in the molecule?
sigma bonds occur along the axis between nuclei whilst the pi bond occurs above and below the π axis, where the p orbital lobes have overlapped
how do you determine what sp orbital hybrid variant a given carbon is in a molecule?
you must count how many different electron groups are attached to it, for example if it was CH4, this would mean that its tetrahedral and therefore sp3, whilst if you were dealing with a C=CH2 molecule, the hybridisation state of the right hand carbon would be sp2 because it is only attached to 3 groups, therefore being triagonal planar
how many different groups are present in carbons that are either: sp, sp2, sp3?
sp3 = 4 groups = tetrahedral
sp2 = 3 groups = triagonal planar
sp = 2 groups = planar
how do you determine the hybrid orbital identity of a carbon atom?
(1) counting how many groups are attached to
(2) deduce the structure from how many groups you’ve counted
(3) link the structure to its designated sp variant (e.g. sp3 = tetrahedral and so on)
if you are trying to deduce the hybridisation state of a carbon and a lone pair is present, do you count it as a group that goes towards the sp numbering?
yes - each lone pair is its own group
sp2 shows us that:
our molecule is planar & the bond angles are 120*
when tackling hybridisation states, how do we teat lone pairs of electrons?
we treat electrons as their own individual groups, contributing to the sp identity
dumb words, what is a resonance form?
a resonance form is a different form of a given molecule where the atom nuclei are in the identical places as before but the electron configuration has completely changed
amide (N attached to carbons - not hydrogens!) nitrogen’s will always have ___ hybridisation
SP2!
2 main rules of resonance:
(1) Thou shall not break a single bond
(2) Thou shall not violate the octet rule [atoms must have 8 electrons in their outer shell - in all resonance forms]
only two things you move when creating resonance structures are:
(1) π bonds [C=C]
(2) lone pairs (:)
when moving lone pairs when constructing resonance structures, what must you always do in order to confirm that you aren’t breaking the octet rule?
you must draw out the lewis structure to ensure you aren’t kicking off any hydrogens when creating double, triple bonds etc
what arrow do we use for resonance forms?
you must use a double headed arrow - NOT an equilibria one however, just a standard double headed arrow
note - something can still be minus charged and yet still also fulfill the octet rule, give an example:
..
-: O :—
oxygen above has eight electrons in its outer shell therefore octet is satisfied, however because oxygen has only one bond it will always posses a single negative charge
two ways in which you can transfer a double [π] bond when creating resonance structures:
(1) moving them to another double bond location
(2) moving the double bond onto a species that can hold a lone pair, hence creating a single bond
what must be the same in all resonance structures?
the overall charge of all resonance structures must all be identical
if a nitrogen atom is noted as neutral, what do we assume?
that a lone pair is present on the nitrogen [nitrogen cannot be neutral without a lone pair]
how do you base your judgment on the charge of C/O/N?
you must look at their numbers of bonds and lone pairs to infer their charge where O has two bonds to be neutral, N has 3 bonds to be neutral and C has 4 bonds to be neutral
if they are missing a bond or a lone pair this will result in a (+) charge and a ( - ) charge will take place as a result of additional bonds or lone pairs above their usual amounts
you can still create negative and positive charges when drawing resonance structures, even if it feel wrong - SO LONG AS the overall charge cancels out at the end to give the overall charge of your starting molecule
you can still create negative and positive charges when drawing resonance structures, even if it feel wrong - SO LONG AS the overall charge cancels out at the end to give the overall charge of your starting molecule
less & more bonds on an atom than that of what is needed for neutrality results in:
positive charge = more bonds than usual
negative charge = less bonds than usual
how many lone pairs does oxygen always want in order to be neutral?
always wants 2 lone pairs and 2 bonds to fulfil the octet rule
if oxygen is neutral, what does this imply?
neutral oxygen implies 2 lone pairs present
