inorganic 3- shapes and isomers Flashcards
Why does a chemical bond form
if the bond (resulting arrangement of the nuclei and their electrons) has lower energy than the total energy of the separate atoms
Define covalent bond
pair of electrons shared between 2 atoms
what is the goal of a covalent bond
to get as close to being an octet by sharing electron pairs
a lewis structure shows — electrons
valence electrons
What is an element with an unpaired electron considered
a radical
How would a lewis structure represent this
What is a 2c-2e bond
2 centre 2 electrons
calculate the number of valence electrons of [BF4]-
what does hyper valence mean
molecule that has an element containing more than 8 valence electrons
is a dative bond any different energetically from a normal covalent bond
no
what is a dative bond
One atom donating a lone pair of electrons in one orbital into a vacant orbital on another atom = dative bond
what hybridisation is nitrogen in ammonia
sp3
How many valence electrons, and therefore pairs of electrons in SO4 2-
equation for formal charge
How do you get to the electrons being hybridised
excite 2s electrons to 2p level
Why can elements get a higher co-ordination number as you go down the group
radius of the elements gets bigger
How would these sulphur electrons hybridise/arrange to form SF6
most energetically stable way to arrange 6 F bonds/ all S-F bonds must be the same energy
how is molecule shape dictated and what assumptions do we make to decide it
electron repulsions. assumption= all bonds are covalent
What type of elements do we not use VSEPR theory to predict molecule shape for
VSEPR applicable to s- and p-block compounds. d-block compounds (complexes) have shapes dictated by the number of ligands
What is the heirachy of electron repulsion
If all sites are equal (octahedral geometry) then where will the lone pairs be paired in relation to one another
lone pairs will be trans (opposite)(180° angle)
Bonding pairs to electro—- substituents occupy less space than those to more electro— substituents.
Bonding pairs to electronegative substituents occupy less space than those to more electropositive substituents.
Where would a lone pair go on this arrangement
will always be equatorial in a trigonal bipyramidal
When deciding a molecule shape, do double bonds or single bonds take up more space
double bonds take up more space
What is a pseudostructure
arrangement of electron pairs whether they are bonding or lone pairs
Where would you want the least electronegative/biggest element to go in a shape
in the middle
Name all the structures and their bond angles
Pentagonal bipy is rarely found experimentally. If something had 6 ligands and 1 lone pair, what would the shape more be like
Octrahedral. A stereo-chemically inactive lone pair localised in s orbitals is distributed evenly around the shape. S-orbitals lone pairs are spherical and do not influence shape;
only lone pairs housed in p orbitals influence shape
What is the structure of a molecule with 2 lone pairs
linear
What pseudostructure vs real structure would BeCl2 be
linear, linear
What pseudostructure vs real structure would BF3 be
trigonal planar, trigonal planar
What pseudostructure vs real structure would SnCl2 be
trigonal planar, v shaped
What pseudostructure vs real structure would NH3 be
tetrahedral, trigonal pyramidal
What pseudostructure vs real structure would CH4 be
tetrahedral, tetrahedral
What pseudostructure vs real structure would NH4+ be
tetrahedral, tetrahedral
What pseudostructure vs real structure would PCl5 be
trigonal bipyramidal, trigonal bipyramidal
What pseudostructure vs real structure would I3- be
trigonal bipyramidal, linear
What pseudostructure vs real structure would PCl6- be
octahedral, octrahedral
What pseudostructure vs real structure would CIF5 be
octahedral, square pyramidal
What pseudostructure vs real structure would IF7 be
pentagonal, pentagonal
What type of molecule notation would BeCl2 be
AX2
What type of molecule notation would H2O be
AX2 E2
What type of molecule notation would CIF5 be
AX5 E
C, N and O are all in the same period, so why do the angles get smaller
Higher space requirements for the lone pairs
This is the predicted shapes for molecules with 5 valence electrons but this changes as to wether one of those valence electrons is a lone pair. What other shapes do these molecules take
Of the other structures for AX5. What is the structure for AX4 E
Of the other structures for AX5, what is the structure for AX3 E2
Of the other structures for AX5, what is the structure for AX2 E3
Which structure would be favoured
lone pairs go in equatorial positions Structure (c) appears most favourable energetically. But we cannot look at the lp-lp repulsion in isolation; (c) looses out when considering the number of bp-lp repulsions, at 90 deg from each other too.
The large number of 90 deg repulsions in (b) and (c) means that (a) is most stable in relative terms,
with fewer repulsions
lone pairs/ double bonds go in what positions
equatorial
What are fluxional molecules
molecules that are an intermediate between two geometries
Is triagonal bipyramidal higher or lower in energy than a square based pyramid
slightly lower
Which is generally favoured
square based; many species show a geometry which is intermediate between the two
7 pair of electrons AX6E predicts pentagonal bipyramid (e.g. BrF6-, SeBr62-, SbCl63-), but what is usually the structure
the real experimental structures are Octahedral with a stereochemical inactive active pair/ Lone pair is a cloud over molecule not housed
in SF4O where would the flourines and the oxygen go. S and O = G6 F= G7
double bonds go in equatorial position to minimise repulsion
If F is more electronegative than Cl what is the difference in bond angle between the two molecules
F-N-F will be smaller. Electron density is closer to F making it easier to have the bonding pairs closer, so there is the furthest distance between the LP and the BP
can atom size and electronegativity effect molecule shape
yes
What elements can VSEPR not predict the shape of
transition metals and most heavy p block elements
How would you work out what shape BrF5 is
How to work out what shape BrF2 + is
What is a Lewis acid
electron pair acceptor e.g. transition metals
What is a Lewis base
electron pair donor e.g. halides
What is a Bronsted acid
donates a H+
What is a Bronsted base
accepts H+
When only does the Bronsted acid/bases definitions work
in aqueous solution
Which would be the Lewis acid and which is the Lewis base
what is gerade symmetry
can be inverted and still the same
what is ungerade symmetry
inverted and shape remains the same but phases are different
When is the only time you use g and u symbolisims
if something has symmetry as it lets the person know what type of symmetry it has
at a nodal plane what is the probability of finding an electron
0
Define transition metal
where the valence electrons are d electrons
What is the order of filling the orbitals 3s, 3p, 3d, 4s
3s, 3p, 4s, 3d
In oxidation or reduction of transition metals where are the electrons lost/gained from
d orbital
How to work out a d electron count (e.g of FeCl3(H2O)3 )
The d-electron count of a metal in a complex is the number of electrons associated with the metal in its formal oxidation state.
What are the two transition metal anomalies that have a different electronic configuration
Cr and Cu
Cr= 4s1, 3d5
Cu= 4s1, 3d10
What would the ion electronic configurations be
What would the ionic configuration be
What would the ion electronic configuration be
If Cr at oxidation= 0 is d6, then what would Cr 3+ be
d3
What is the d electron count of Ni 2+
What is a co-ordination complex
a central atom or ion (Lewis acid) coordinated to one or more ligands (Lewis base) by a coordinate bond
What is the shape of a complex dictated by
number of coordinated ligands
What is the co-ordination number of cobalt
6
What is the co-ordination number of cobalt
6
What is a mononuclear complex
What is a binuclear complex
What is a polynuclear complex
What is the difference between a monodentate, bidentate and tridentate ligand
Bidentate ligands have two donor atoms, and can bind to one or two other atoms. Other than a complex, what else can this form
rings (size dictated by number of atoms separating the donors in the ligand)
How does ETDA bind to form a ligand complex
It is a hexadentate ligand
What are ambidentate Ligands
What are each of these things
In name complexes, where is the central atom part of the name located
At the end with the oxidation number
What does the tetra prefix mean in regards to ligands
4 bond sites
What are each of the metals these complex names relate to
What are hard and soft metal centres in complexes
soft= more polarizable
hard= less polarisable
Define a ligand
A group/atom that gives a metal centre a pair of electrons, normally through an available lone pair e.g H2O or NH3
How does the electron cloud of the ligand interact with the available orbital on the metal (wether metal is receiving electrons or giving them)
What are some examples of bidentate ligands
They can also function as monodentate ligands
Can a carbon chain radical be a ligand
yes
hard cations are more compatible with hard/soft ligands
hard cations= compatible with hard ligands (hard acids and hard bases)
soft cations= compatible with soft ligands (soft acids and soft bases)
hard cation- hard ligand interactions are ionic/covalent
more ionic than covalent
soft cation-soft ligands interactions are ionic/covalent
more covalent (greater overlap)
would F- form a better complex with Ti or Pd
Ti. (hard-hard interaction) Flourine is a hard base and Pd is a soft acid (low charge density) whereas Ti is a harder acid (high charge density)
Trend in transition metals as to wether they make hard or soft metal ions/ acids
Becomes softer down the group
Early transition metals= hard; are small ions with large charge density
Later transition metals= soft; have all their d electrons
If something is highly electronegative will it be hard or soft
hard; less polorizable
Why is water left out of constant equations
its concentration is assumed to be constant in aqueous solutions
What does a larger/smaller stability constant mean
constant= large; a ligand binds to the metal more tightly than H2O
small= a ligand binds to metal less tightly than H20
What are typical values for the stability constant Kf of a metal ion
1-13
A chelation reaction results in an increase/decrease in the number of molecules in solution
increases molecules in solution
In a mono dentate ligand reaction, the number of molecules increases/decreases/ stays same
stays the same
Which side of the reaction does the equilibrium lie is the equilibrium constant is high
lies to right
if the equilibrium lies to the right there is a large/small △G
large negative △G
Which reaction will have the greater value for K (equilibrium constant)
Which complexes are more stable; chelate complexes or mono-dentate metal / ligand complexes.
a complex containing one (or more) 5 or 6 membered chelate rings is more stable
{i.e. stability (or formation) constant is larger} than the one without the ring
How is the chelate effect effected with ring size
The chelate effect decreases with increasing ring size
What is square planar shape
What is Constitutional/ structural isomerism
Compounds with the same empirical formulae but with different atom binding sequences. There are several classes in this
-co-ordination isomers
-linkage isomers
-polymerisation isomers
What is a co-ordination isomer (constitutional isomerism)
What is linkage isomerism
-two or more coordination compounds in which the donor atom of at least one of the ligands is different
can only exist when the compound contains a ligand that can bond to the metal atom in two (or more) different ways
What is ionization isomerism
Occurs when isomers produce different ions in solution, often manifest itself by the exchange of a ligated anion with a counterion:
What is geometrical isomerism
Which isomers are cis and trans
What is the optical isomer for this
What is an optical isomer
A compound that is non-superimposable on its own mirror image is an
What are the optical isomers of these
The trans -isomer has mirror symmetry and is therefore not optically active. What are the optical isomers of these (enantiomers)
Why are there relatively few complexes with coordination numbers 1 and 2
because they are exposed to attack by additional ligands, so increasing their coordination number
This is a complex with a co-ordination number of 1. Usually these are readily attacked, but why could this one be stable
the ligand ‘protects’ the metal by steric crowding
Co-ordinaiton number of 3 is rare amount d-block elements; what Is needed for a stable CN=3 complex
large and kinetically stable ligand
for CN=4, what d-block elements will take tetrahedral and square planar
tetrahedral- centre atom is small/ our ligands are big
square planar- for larger d8 metal ions – Rh+, Ir+, Pd2+, Pt2+
What are the two shapes for CN=5
trigonal bipyramidal and square pyramidal
What would be the geometric isomer of this compound
What would be the geometric isomer of this compound
if something is non super imposable they are chiral/not chiral
Chiral isomers are non-superimposable mirror images of each other
What is the oxidation state and dn configurations for the metal
Cu=29 electrons/ group 11
What is the oxidation state and dn configurations for the metal
V =23 electrons/ group 5
What is the oxidation state and dn configurations for the metal
Au=79 electrons/ group 11
What is the oxidation state and dn configurations for the metal
Fe=26 electrons
What charge/ oxidation state is a CN ligand
-1
What is the d electron count for Ni (group 10)
What is the d electron count for Co
What is an en ligand
-1 Ethylenediamine
What is the bond order of NO3-
(1+1+2)/ 3 [1+1+2 is adding the bonds and 3 is dividing by number of bonds with double being counted as 1]
They are all ligands
What structure does [PoF5] have
octrahedral and square based pyramidal are in equillibrium
What structure does [GeCl3]- have
What structure does [AlCl2]+ have
What structure does [BrF6]- have
What structure does [Sb(O)Cl4]- have
Why is Cl not -1 in first ligand
Which one is cis and which one is trans
Which one is fac and which one is mer (can only be done on octrahedral complexes for **tridentate chelates/ligands)
fac (on one face)
Which isomer is fac and which one is mer
What are delta and lambda isomers
optical isomers
Just a
cis and trans isomers/ with an optical isomer (delta and lambda) possible
Just b
only mer and fac
Just c
cis and trans
Just d
optical isomers
Just e
