Colour and Magnetism

Question 1

the size of delta oct is the same as? and what does it affect?

Answer 1

it is the size of the energy gap

size affects colour and magnetism

Question 2

strong field ligands

Answer 2

bind to metal ion strongly - greater ligand to metal electron repulsion leading to a large delta oct and few unpaired electrons = low spin

Question 3

weak field ligands

Answer 3

bind weakly to metal centre and therefore there is less repulsion and smaller splittings between d orbitals leading to smaller delta oct. more unpaired electrons = higher spin electronic states

Question 4

colour and inverse relationship

Answer 4

colour is observed when an object reflects colour and absorbs the complementary colour
inverse relationship: delta oct is small when lambda max is large etc.

Question 5

colour in transition metals

Answer 5

because of splitting of d orbitals in the CFT, d orbitals have different energies and electrons can absorb light/energy and move to higher energy d-orbitals (if there is room)

Question 6

equation for delta energy of electrons

Answer 6

delta E electrons = planks constant . v = planks constant . speed of light/lambda

Question 7

ligand effects

Answer 7

strong field ligands absorb large amounts of energy for electrons to move (absorb light at lower wavelengths)
opposite for weak field ligands
ligands are always the same (weak or strong)

Question 8

other effects on colour

Answer 8

changes in oxidation state (higher ox = higher delta oct splitting and therefore more attraction between metals and ligands)
geometries - delta tet ~ 4/9 delta oct

Question 9

magnetism

Answer 9

electrons spin and move around the nucleus creating electric currents in closed loops which create magnetic dipole fields - align with external fields
more unpaired electrons = greater attraction to a magnetic field
usually d electrons (not used when ligands bond - not covalent)
low and high spin geometries

Question 10

measurement of magnetic properties

Answer 10

measure attraction to evaluate number of unpaired electrons or n (identity, ox no, geometry, high/low spin because d4-d7 have a choice)
high - unpaired electrons and small delta oct
low - electron pairing
Guoy balance - paramagnetic seem heavier as the unpaired electrons are attracted to the external magnetic field
the weight gives us magnetic susceptibility (chi)
electron spin and orbital angular momentum lead to paramagnetism - first row transition metals are mainly just spin

Question 11

equation for mew off (BM)

Answer 11

effective magnetic moment = 2.828 (chi M . T) ^1/2

molar magnetic susceptibility is M
T is kelvin

Question 12

equation that looks a spin only

Answer 12

mew SO = square root (n(n+2)

Question 13

spin crossover

Answer 13

at lower temps ligands move closer causing higher delta oct and this can change spin