Inorganic Chem test 2

Close packing that maximizes interatomic contact

Close packing that minimizes interatomic contact

Hexagonal close packing

6 spheres surround each, so coordinate number is 6

Cubic Close packing

• ABCABC

• 12 neighbors

• Coordinate number = 12

Hexagonal close packing

• ABAB

• 12 neighbors

• Coordinate number = 12

Unit Cell

• most basic and least volume consuming repeating structure of any solid

• repeats itself = lattice

• Can be cubic close packed (face centered packed)

• hexagonal close packed

What type of holes can close packing structures have?

• Octahedral

  • surrounded by 6 spheres

• Tetrahedral

  • surrounded by 4 spheres

Simple cube

• primitive cube

• Basic

• Efficiency is 52%

• 6 neighbors

• Coordinate number = 6

Body-centered cubic

• bcc

• Sphere in the middle

• Efficiency is 68%

• Coordinate number = 8

• 1 sphere in the middle, and outer corners spheres = 1 leading to 2 complete spheres total inside

Face-centered cubic

• 74% efficiency

• Coordinate number = 12

• Each of the 8 spheres add up to 4 complete spheres inside

Number of spheres per unit cell?

8 × 1/8 = 1

Alloys

A mixture or compound with 2 or more metals or non metals, alloying it with resistance to corrosion or heat.

• stainless steel is an alloy steel

Resistance

• resistivity x length of wire/ cross section of wire

• inverse of this is electrical conductivity

• metals : as temperature increases, resistance increases, conductivity decreases

• semi conductor : as temperature increases, resistance decreases, conductivity increases

As temp increases

Conductivity decreases

Band

A group of MOs where the energy differences between are so small that the system behaves as if continous

• farther a part the bands are the less of a conductor it is

• Fully touching is conductor

• far away is an insulator

Insulator band

Metal with partially filled lower band

Metal with overlapping occupied and empt bands

Semiconductor

Fermi level

• chemical potentials of electrons in a solid (conductor, semi conductor, insulator

Intrinsic semiconductor

• no dopants

• small band gap

• Completely filled and completely empty bands

• Conductivity increases with temperature

Extrinsic semiconductor

• contains dopants (a small amount of an element) with more n-type or less p-type than 4 e-

Reduction Oxidation reaction

Oxidation = losing one or more electrons

Reduction = gaining one or more electrons

standard Gibbs free energy change

ΔG° = - nFE°_cell

n= how many e- transferred

Faraday’s constant = 96485

E°_cell = standard cell potential in volts

Cathode vs anode

To find E°_cell

• Cathode (reduction E°_cell) - Anode (oxidation E°_cell)

• remember that if it is oxidation the E°_cell is going to be positive

To write a balanced spontaneous cell equation

1. Write the two separate equation as a oxidation and reduction equations

   1. Reduction = cathode

   2. Oxidation = anode

      1. E cell = +

2. Than combine for the balanced equation

3. To find E cell = cathode - anode

   1. If positive than it is sponateous

4. To find Delta G

   1. Delta G = -(how many e- transferred) (Faradays constant)(E cell)

Lattice energy

• delta U

• change in internal energy from gas to solid