Older content exam 2 review

Question 1

What is “linear combination of atomic orbitals”?

Answer 1

each molecular orbital is constructed from a superposition of atomic orbitals

Question 2

Why are some diatomic molecules not energetically favorable to form?

Answer 2

The difference in energy between the bonding and antibonding orbitals are asymmetrical

Question 3

Wavefunctions _____ be either symmetric or antisymmetric around the molecules’ center of symmetry

Answer 3

MUST

Question 4

What orbitals overlap to form energy bands? Which orbitals overlap first?

Answer 4

atomic, outer

Question 5

What is the fermi energy?

Answer 5

the energy level of the maximum filled orbital at 0K

Question 6

What is the work function?

Answer 6

difference between the fermi level and vacuum

Question 7

______ orbitals can’t change without excitation with constant potential, _______ orbitals can

Answer 7

atomic, molecular

Question 8

Why are orbitals in Si oriented to the four corners of a tetrahedral?

Answer 8

to minimize electron repulsion

Question 9

Is the energy gap a physical space?

Answer 9

no, the band gap doesn’t have a physical location

Question 10

If we decrease R in Si, what happens to the energy band?

Answer 10

it gets bigger

Question 11

Does a bigger or smaller effective mass give a greater conductivity?

Answer 11

a smaller effective mass

Question 12

What is the band gap?

Answer 12

energy difference between CB and VB

Question 13

At 0K, are there any electrons in the CB?

Answer 13

no, they’re all in the VB

Question 14

What is the density of states between n=3 and n=4?

Answer 14

2

Question 15

What’s the density of states at n=1?

Answer 15

1

Question 16

What happens to a metal with a lower fermi energy?

Answer 16

The number of electrons in the valence band increases

Question 17

What is electrical work (eV) after combining metals?

Answer 17

the difference in the metals wavefunctions

Question 18

What is the Pauli exclusion principle?

Answer 18

no two electrons can have the same set of quantum numbers

Question 19

When two metals are brought together the Fermi energy level ______

Answer 19

aligns

Question 20

Bohr approximation is used to approximate if the electron is _____ _______

Answer 20

spatially delocalized

Question 21

In order for appreciable transport, we need _____ _____

Answer 21

spacially delocalized charge carriers

Question 22

The energy levels that donor electrons fill are a function of

Answer 22

1. # of donors
2. donor orbital energies
3. CB edge

Question 23

If a band is full of electrons, those electrons ____ contribute to conduction

Answer 23

don’t

Question 24

Any _____ bands can contribute to conduction

Answer 24

unfilled

Question 25

Do electrons have the same effective mass in 3p and 4s bands?

Answer 25

no, their acceleration is different