Chapter 1: Bonding, Structure, And Defects Flashcards
What happens to the size of an anion and a cation when it gains/lose electrons?
- Anions get bigger
- Cations get smaller
Where in the periodic table do we have the most electronegative elements?
Top right (Fluorine)
What sort of bonds exists?
- Metallic
- Covalent
- Ionic
What would the bonding type of P_4O_10 be?
Covalent oxide (small electronegativity difference)
What is the oxidation number of F?
-1
What is the oxidation number of O?
-2 (oxide)
-1 (peroxide)
-1/2 (superoxide)
(Except in a bond with F)
What is the oxidation number of H?
+1 (proton) or -1 (hydride)
What sort of packing does a hexagonal close-packing (hcp) have?
ABABABAB …..
Which is the closest packing of the cubic structure?
Face centered packing
What sort of packing does a cubic close-packing (ccp) have?
ABCABCABC …
What types of holes exists?
Octahedral and tetrahedral
What sort of parameters are there for tetrahedral holes?
- Surrounded by 4 large spheres
- Relatively small
- 2 per sphere
What sort of parameters are there for octahedral holes?
- Surrounded by 6 large spheres
- Relatively large
- 1 per sphere
What is the packing and filling of the rocksalt structure? (AX)
Fcc with all octahedral holes filled
What is the packing and filling of the fluorite structure? (AX_2)
- Fcc of A[2+] with X[-1] in all tetrahedral voids
OR
- Simple cubic X[-1] with A[2+] in every other cube
What is the packing and filling of the perovskite structure? (ABX_3)
Fcc of A[+3]X with B in octahedral voids in-between AX_6 units
What is the conduction and the valence band?
- Conduction band: lowest unoccupied band
- Valence band: highest occupies band
How is the band gap defined?
- Energy range where no electron states can exist
- The energy difference between CB and VB
What sorf of defects are there?
- Point defects (0D)
- Line defects (1D)
- Planar defects (2D)
- 3D
What are the point defects?
- Interstitials (in- and extrinsic)
- Vacancies
- Substitutional
What are the line defects? [NEEDS EDITING]
- Edge dislocation
-
What are the planar defects?
- Plane of point defects
- Row of dislocation
- Grain boundary
What are the Kröger-Vink notation for an oxygen and a metal vacancy?
- v_O++
- v_M’’ (divalent)
What is an effective charge?
It is the actual charge of the species minus the actual charge that the ideal perfect reference structure would have had in the same structural element
What would the effective charge of a metal vacancy be?
Negative the oxidation state
How would you describe an oxidized metal, e.g. Ni2+ to Ni3+?
As a hole, h+
How would you describe a reduced metal, e.g. Ni2+ to Ni1+?
As an electron, e-
How is a proton described using the K-V notation? (in an oxide)
As an hydroxide ion subst. an oxide ion ==> OH_O+
NOT as a single positively charged interstitial H
Why aren’t the single proton described as such in the K-V notation? (in an oxide)
Because it will be drawn into the electron cloud of an anion close by
How are the effective positive and negative charges in an ionic compound related?
They have to be compensating each other fully, as an ionic compound has to be electrically neutral
In the elctroneutrality condition, what sort of concentration is used here?
Charge concentration, not species
What sort of defects appear in a stoichiometric compound?
Schottky, Frenkel, and anti-site defects (swap cation/anion)
