Ionic Lattices, Super/semiconductors

Question 0

The hoe of ionic structure that is take on depends on the

Answer 0

Relative sizes of atoms

Question 1

What ar the basic properties of a ionic substance

Answer 1

High melt and boil
Solid at room temp
Conduct when molten or in solution

Question 2

If the ions are roughly the same size it will be a

Answer 2

Caesium chloride structure

Question 3

If one ion is much larger than the other he structure taken will most likely be a

Answer 3

Sodium chloride structure

Question 4

Describe a caesium chloride lattice

Answer 4

Each caesium and chloride surrounded by 8 of the other ion
Having an 8:8 coordination
Look at ionic radii in DB

Question 5

Describe the sodium chloride lattice

Answer 5

Sodium is much smaller than the chloride
Only six chlorides can accommodate around a sodium
6:6 coordination

Question 6

How do you predict the type of ionic lattice

Answer 6

Calculating the ionic radius ratio

Dividing the positive radius with the negative radius

Question 7

What is the special feature of Superconductors

Answer 7

Has zero electrical residence at very low temperature (0k)

Question 8

What is the temperature that below which the superconductors will work

Answer 8

Critical temperature Tc

Question 9

What is the compound sometimes known as 1-2-3 superconductors

Answer 9

YBa2Cu3O7

Question 10

What is the future aspiration for superconductors

Answer 10

Reducing energy Loss in power transmission

Question 11

What are semiconductors sometimes referred to

Answer 11

Metalloids

Question 12

What is a semiconductor

Answer 12

Electrical resistance of a semiconductor decreases as the temperature increases (electrical conductivity increases with temp)

Question 13

Heat is the photoelectric effect

Answer 13

When electrical conductivity increases on exposure to lights

Question 14

How does this semiconductor work

Answer 14

Increase temp cause some bonding electrons to break leaving POSITIVE HOLES
when voltage supplied these holes move through lattice
This can be effected by DOPING to improve conductivity by adding impurities

Question 15

What are the two types of doping

Answer 15

Doping crystals of germanium or silicon with phosphorus adds an extra electron = N TYPE SEMICONDUCTOR
Surplus of negative charge

Doping with boron or aluminium only 3 outer electrons more positive holes present = P TYPE SEMICONDUCTOR
Surplus positive charge

Question 16

What is a p-n junction

Answer 16

Formed between two layers of a n-type and a p-type

Excited electrons and positive holes move. Opposite directions ( sunlight converted too electricity )