inorganic (Benniston) Flashcards
What do Zinc enzymes do?
Alcohol dehydrogenase-
breakdown of ethanol to acetaldehyde.
What do Iron enzymes do?
Haemoglobin- transport of O2 .
What do Copper enzymes do?
Removal of superoxide O 2-.
What do Colbalt enzymes do?
vitamin B12 methylation
reactions.
Define transition metals.
Transition Metal- an element for which
an atom has an incomplete d-subshell or
which gives rise to a cation with an
incomplete d-subshell.
What are the names of the 5 d-orbitals?
dz^2
dx^2-dy^2
dxy
dxz
dxy
when would all of there orbitals be degenerate
when the metal is in it gaseous phase
why are the d orbitals not degenerate
dxy, dxz, dzy orbitals points inbetween the axis whereas dx^2 and dx^2-dy^2 is along the axis so when the ligands bind they will bind along the axis the dx^2-dy^2 and dx^2 will be higher in energy.
which orbitals are degenerate with each other
dxy, dxz, dyz are all degenerate with each other
dx^2 and dx^2-dy^2 are also degenerate with each other
What is the equation for learning number of d electrons
No. of d electrons = Group Number – Oxidation State
What is the first law of thermodynamics
Energy is conserved. It can be transferred from place to place and
converted between different forms, but the total energy of system +
surroundings is always the same
How is the first law of thermodynamics expressed for different systems
Total energy, also called internal energy has the symbol U
Isolated system: ∆U = 0
Closed system: ∆U = q + w
Physical Properties of d-block metals
- Most are hard, ductile and malleable with
*high electrical and thermal conductivities.
define ductile
Ability to be stretched or pressed into a shape without heating
define malleable
Ability to be shaped easily
without breaking
what are typical metal structures
hexagonal closed packed (hcp), cubic closed packed (ccp) or body centred cubic (bcc).
what are the exceptions of the typical metal structures
Mn, Zn, Cd and Hg
trends with metallic radii as you move across a period and why
gradual decrease in metallic radii as we move across the period the
effective nuclear charge increases so a high charge density with relatively similar amounts of shielding pulls electrons closer in the nucleus
what is Lanthanide Contraction and how does it work
the lanthanide contraction refers to the steady descrease in the size of the lanthanide series, this contraction occurs because the additional electrons are poorly shielded by the 4f electrons leading to an increase in effective nuclear charge and a decrease in atomic radius
which orbitals point along the axis and which point between them
dz^2 and dx^2-y^2 along axis
Dxz Dxy and Dyz point in between the axes
what are the assumptions for crystal field theory
- Ligands are point negative charges
- The binding withing a complex is purely ionic
- Metal ion is in the gas phase
- Bring the negatively charged ligands from infinity to generate the complex
outline the crystal field theory
1) the metal ion in the gas phase cannot sense the ligands. All 5 d orbitals have the same energy (degenerate)
2) use a thought experiment and start to move the ligand closer along the axis
3) when ligands get close but not bound all the d-orbitals sense the point negative charges, they all destabilise
4) attach the ligand
What happens to the orbitals in crystal field theory for an octahedral complex
1) As the ligands approach from infinity along the x,y and z axes the electrons in the d-orbitals start to sense them.
2) Since negative charges are being brought closer together the dz2 and dx2-y2 become destabilized and rise in energy +3/5 delta O
3) The other three orbitals are not so affected because they point in between the axes and lower in energy. -2/5 delta O
What happens to the orbitals in crystal field theory for an tetrahedral complex
Ligands do not point along any axis and now actually point between them
Now the three d-orbitals (dxy, dyz and dxz) are better aligned with the ligands and the other two (dz2, dx2-y2) point in between.
1: As the ligands approach from infinity in between the x,y and z axes the electrons in the d-orbitals start to sense them.
2: Since negative charges are being brought closer together the dxz, dyz and dxy become destabilized and rise in energy.
3: The other two orbitals are not so affected because they point along the axes and lower in energy.
4: The splitting term D(tet) is smaller than D(oct). The ratio is ~ D(tet) =4/9 x D(oct) for the same ligand type.
What happens to the orbitals in crystal field theory for an square planar complex
The two ligands along the z axis are pulled away from the metal - tetragonal distortion
1) As the two ligands along the z-axis are removed the d-orbitals with a z component lower in energy.
2) The ligands in the x-y plane are pulled in more and so d-orbitals with a x,y component rise in energy.
Eventually the two ligands are removed to infinity and the dz2 orbital falls in energy to below that of the dxy.
what is delta O
ligand field splitting
what is P
pairing energy, the energy required to pair electrons up in orbitals
what happens if P is larger than delta O
If the pairing energy is greater than delta o a weak field high spin complex is formed
what happens if delta O is greater than the pairing energy
If delta o is greater than the pairing energy then a strong field low spin complex is formed
what happens after d8 in terms of high/low spin
after d8 onward it makes no difference as the electron can only go in one place therefor the high/low spin notation is meaningless
how does the charge effect delta o
The value of ∆o increases with increasing charge on the metal ion.
define diamagnetic
all electrons are spin paired and complexes are repelled by a magnetic field.
define paramagnetic
complexes contain unpaired electrons and are attracted by magnetic fields.
what is the spin only formula and why is it useful
Measurement of effective magnetic moment is useful as it can distinguish between high/spin and low-spin and help determine coordination geometries
effective magnetic moment = square root of n(n+2)
where n is the number of unpaired electrons
Measured in Bohr magnetrons
define paramagnetism
the spins are randomly orientated in the material
what is ferromagnetism
Above a certain temperature (Tc-Curie temperature) the thermal energy is enough to overcome the alignment and normal paramagentic behavior prevails
define antiferromagnetism
the spins become aligned anti-parallel leading to a diamagnetic material
define ferrimagnetism
some spins are aligned anti-parallel to each other but overall there is a finite magnetic moment
what is the Jahn-teller effect
“If a ground-state electronic configuration of a non-linear complex is orbitally degenerate the complex will distort so as to remove the degeneracy and achieve a lower energy” - theory used to explain the distortion of octahedral and tetrahedral complexes
when would square planar complexes be more or less favored
less favored sterically especially for large ligands. Complexes are found for only a few metal ions and dominated by d8 transition metals (e.g., Ni2+, Pd2+ and Pt2+)
Need (i) Non-bulky ligands, (ii) Strong-field
ligands (i.e CN-).
why do complexes have color
Energy is required to move an electron from the t2g level to the eg level a certain frequency of light is required to promote the electron.Only a part of the white light continuum is of
the correct energy and so some of the light is
“left behind.” This gives a complex its colour.
What is the beer-lamber law
Amax = emax .c . l
A = absorbance
e = molar absorption coefficient dm^3mol^-1cm^-1
c = concentration
l = cell path length cm
Knowledge of the molar absorption coefficient is very useful as it gives some indication about how allowed a transition is
what are d-d transitions
a shifting of electrons between the lower energy d orbital to a higher energy d orbital by absorption of energy