Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Inorganic > Slater - Solid State Chemistry > Flashcards

Slater - Solid State Chemistry Flashcards

1
Q

What 5 pieces of information can be determined by theXRD experiment?

A

Size, shape and electron density distribution within the unit cell
Type of atoms and position of atoms within the unit cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What were the 7 types of crystal systems?

A 
Triclinic 
Monoclinic 
Orthorhombic 
Tetragonal
Trigonal
Hexagonal
Cubic
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are the four types of centring of a unit cell

A

Primative
Body centred
Face centred
Base centred

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is Braggs law

A

Lambda = 2dhkl sin ø

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the indexing pattern for a cubic unit cell

A

1/dhkl = (h^2 + k^2 + l^2) / a^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Indexing pattern for tetragonal

A

1/dhkl = (h^2 + k^2) / a^2 + l^2/ b^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Indexing pattern for orthorhombic

A

1/dhkl = (h^2) / a^2 + k^2/ b^2 + l^2/ c^2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What equation do you use that incorporates braggs law to find a ( bond length )

A

4a^2 = lambda^2 (h^2 + k^2 + l^2) / sin ^2 ø

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Explain thermogravemetric analysis

A

A precise microbalance used to monitor the mass whilst it is heated under a variety of atmospheres
Information about component ratios can be calculated but not their defects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the general formula for the perovskites crystal

A

ABO3 where a is the large cation and b is the small cation
Close packing spheres
Small cation occupies 1/4 of octahedral holes
Primative structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the two groups of defects

A

Intrinsic - stoichiometric and therefore not changing overall ratio
Extrinsic - non-stoichiometric used to improve properties such as conductance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the two intrinsic defects?

A

Schottky and frenkel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the driving force for intrinsic defects?

A

Toss off between favoured entropy changes (increased disorder) and unflavoured enthalpy changes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the third law of thermodynamics

A

Crystals can have complete atomic order only at zero kelvin - at all other temperatures disorder will reduce the free energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Explain schotty defects

A

Introduction of vacancies in an anion and cation site following the stoichiometry of the crystal. I.e. 1:1 removed if formula is NaCl but if MgCl2 then 1:2 removed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Explain frankel defects

A

Displacement of the cation or anion into an interstitial site within the lattice
Normally cation because they tend to be smaller

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

When is it not possible for schotty and frankel defects to occur

A

In non stoichiometric solids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Explain schotty defects in terms of entropy and enthalpy

A

Increased defects, increases entropy and increases enthalpy

Enthalpy is related to but not equal to the size of the lattice energy in schotty defects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Explain the frankel defects in terms of enthalpy, instability and repulsion

A

Moving a cation towards the interstitial site will move the ion closer to a neighbouring cation which will increase repulsion between the two positively charged species leading to a more unstable material
Enthalpy Change is related to energy required to move the io into a less favourable site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

In a large crystal, how many ions do we have in a one mole lattice ?

A

Avogadros constant 6.02x10^23

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What is the equation used to calculate the entropy change per mole of crystal changed?

A

S=k lnΩ

Where k = Boltzmann constant
S = number of statistical arrangements (typically avagadros number)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What eventually happens with the enthalpy entropy balance with schotty defects

A

Eventually delta g and delta h will balance out and the formation of a schotty defect will no longer be favourable

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

As you decrease the temperature, the number of defects…

A

…decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What are the most favourable intrinsic defects?

A

Schotty defects

Because a frankel defect usually involves an octahedral cation moving into a tetrahedral site which is highly endothermic and unfavourable. Partly due to size of ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Which 3 examples prefer frenkel defects and why
AgCl, AgBr and AgI Displacement of the Ag+ into a tetrahedral interstitial site is preferred because Ag prefers tetrahedral coordination as opposed to octahedral coordination
26
Why would frenkel defects be favoured?
Any vacant sites that are unoccupied by cation mean that the anions can displace from their original site and and displace to the vacant square - good for conductance
27
At 800 degrees C, how many defects are there in a cube of crystal approximately 20 unit cells long (100 angstroms)
1
28
Why is it hard to predict the number of defects at low temperatures?
Thermodynamic vs kinetic effects At low temperatures the cations motion is typically frozen so defects cannot be moved
29
How can you prepare a solid with high defects
Prepare at high temperatures and rapidly cool so the ions don't have time to move back, leading to more defects in the solid than expected
30
Why are some lattices such as TiO seen as metallic?
Overlap of the cations T2g orbitals forms a partially filled band of electrons therefore leaving the solid with metallic properties. The band is filling the whole structure, not truely ionic
31
What are the two types of extrinsic defects
Aliovalent - doping vacancies with ions of different charge | Isovalent - doping with ions of the same charge
32
When doping, what is the most important factor to consider?
Ionic size - needs to be similar to the ionic site
33
When doping a crystalline solid, how is the excess charge of the positive charge balanced?
The structure will contain pockets of electrons in anion vacancies. The structure will have an Imbalance in numbers of cations and anions therefore resultant charge requirements are met. The defects provide colour. Also transition metals can adopt different oxidation states giving a mechanism for maintaining charge balance when defects are created
34
Give three examples of non stoichiometric salts
FeO KCl FeO
35
What happens to non-stoichiometry when temperature increases
The entropy term T delta S increases with increasing temperature therefore an increase in temperature increases the value of x.
36
How is a solid classified as non-stoichiometric?
1) chemically significant composition range (measured under chemical analysis) 2) unit cell size varies linearly (vegards law - deviations occur at high defect concentrations)
37
What does the composition of a non-stoichiometric solid depend on?
Partial pressure of O2 in equilibrium with solid The chemical potential of O2 must be equal to chemical potential of the solid When enthalpy change is small, there's a significant composition range
38
How does the size of the unit cell allow determination of non-stoichiometric solids?
As composition of the cation decreases, the size of the unit cell increases - interaction between defects results in non-linear behaviour
39
In a non-stoichiometric solid, how does the interplay of enthalpy and entropy change dictate the structure?
Entropy favours high concentration of defects and random distribution of defects Enthalpy favours small concentration of defects and an ordered distribution of defects
40
What are point defects?
Non-interacting defects, usually metallic compounds that have d orbital overlaps
41
Explain the structure of SrFeO2.5 and explain the change in structure upon hearing
Vacancies order to form brownmillerite with vacancies located in alternative layers leaving layers of tetrahedrally and octahedrally coordinated Fe. Upon heating, a transition occurs at approximately 850 degrees Celsius where: - Oxygen vacancies become randomly distributed - a deficient oxygen perovskite is formed - Increase influence of entropy as temp increases
42
Give two methods that allow variations of oxidation states of transition metals
1) formation of very high concentrations of oxide ion vacancies (reduction with hydrides) e.g. CaH2 2) reduction of Fe oxidation stage while maintaining low vacancy content e.g. PVDF and -CH2CF2- 400 degrees c
43
Within perovskites the cations occupying A can be....
Different oxidation states of the same cation
44
How are structures ordered?
Ions with different sizes and/or charges will tend to prefer order to minimise strain and electrostatic repulsion
45
Explain the large perovskites structure
A unit twice as large as the conventional perovskites that is face centre with systematic absences such as Sr2FeMoO6
46
Explain the Ruddlesden-Popper structure
Perovskites type units separated by rock salt type layers A(n+1) B O(3n+1) E.g. Sr Ln 0.5 Sb 0.5 O4
47
On an electronic spectroscopy spectra, what gives rise to unsymmetrical peaks
eg--> t2g
48
When analysing spectra, what should be commented on?
Number of bands Energies of bands Intensities of bands Width of bands
49
Why does crystal field stabilisation energy fail?
It ignore electron electron repulsion
50
How does the repulsion energy of xz and z^2 compare to xz and z^2?
Yz and z^2 have less repulsion than xz and z^2
51
When labelling orbitals in CFSE what does T and E stand for
``` T = 3 triplet E = 2 doublet ```
52
What does the orgel diagram show
The relationship between the d1, d4, d6 and d9 showing the ground state. This is identified where all of the lines cross over. For these four configurations you will observe a single band with energy equivalent to delta.
53
When you see a g subscript, what does this relate to?
Octahedral complexes
54
Eg to eg transition has which symmetry and which state?
3A2g | Single find symmetry
55
Eg to t2g transition has which symmetry and which state?
3 fold symmetry therefore 3T2g
56
T2g to t2g transition has which symmetry and which state?
3 fold degenerate low energy | 3T1g
57
When does la Porte selection rule apply?
Only to octrahedral
58
What three factors determine the Band widths
Vibrations Spin orbit coupling Reduced symmetry
59
If vibrations are the same and the two vibrationsl lines run (A) parallel (B) antiparralel What would you expect
(A) essentially the same energy and therefore a sharp peak | (B) large energy differences therefore big energy variation and broad peak
60
How does spin orbit coupling affect the broadness of s peak
Typically a small effect but causes splitting of T terms
61
How does Jahn Teller affect the peak broadness
Removes the degeneracy of the eg level resulting in splitting of the 2Eg term which causes the peak to become more broad and asymmetric
62
On a tanabe sugano diagram, what is the difference between the left and the right of the diagram
Left is high spin | Right is low spin
63
What is MLCT favoured by
Metals with low oxidation state and ligand with empty low energy orbitals (usually pi*)
64
What is LMCT favoured by
Usually m in high oxidation states and ligand with low ionisation energy

Inorganic (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions