Lecture 2

Question 1

Silicon

Answer 1

4 bonds (14, 1s2 2s2 2p6 3s2 3p2)

3s2 3p2 - 4 valence electrons

Bonds through covalent bonding

Question 2

Valence electrons

Answer 2

Can interact with other elements (cause reactions)

Outermost electrons

Question 3

Covalent bonding

Answer 3

Very strong bond

Share electrons

Organic materials (C)

Si (inorganic-IV)

Question 4

GaAs

Answer 4

III-V

Combination of covalent and ionic bonds

Covalent bonding predominant

Question 5

Ionic bonds

Answer 5

Fc - Coulomb force of attraction

Very strong as well

NaCl (insulator)

Ions have a stable electronic configuration (similar to noble gas)

Question 6

Si at T-0K

Answer 6

An insulator

No free electrons - Valence electrons cannot move in electric field (crystal)
— add energy

Question 7

In order for Si to conduct electricity, it needs…

Answer 7

Some form of energy to excite valence electrons to a higher energy level

• Thermal energy (by raising the temp)
• Light Excitation (photons - smallest amount of quantum light, optical energy)
• Collision of energetic electron with electron in crystal lattice (pure mechanical energy)
• Doping

Question 8

Quantum mechanics

Answer 8

Predicts the way in which electrons behave in solids - the light is quantized

Question 9

Photon

Answer 9

Smallest discrete unit of energy

Question 10

1918 Planck

Answer 10

Discovery of energy quanta

Question 11

1921 Einstein

Answer 11

Law of the photoelectric effect

Question 12

1922 Niels Bohr

Answer 12

Structure of atoms and radiation emanating from them

Question 13

Bohr postulates

Answer 13

Electron exists in certain stable circular orbits about the nucleus and does not give off radiation

Electrons may shift to an orbit of higher or lower energy by absorbing or emitting a photon of energy (hf)

Angular momentum is quantized (p=mvr)

Question 14

Light emission

Answer 14

Higher to lower energy level

Gives off photons

Question 15

Light Absorption

Answer 15

Lower to higher energy levels

Absorbing photons

Question 16

Heisenberg Uncertainty Principle

Answer 16

The more precise you know the position of a particle, the less precise you know the momentum of the particle

The more precise you know the time, the less precise you know the energy

Question 17

Metallic bond

Answer 17

Metals - lose electron

3 valence electrons - outer shell is partially filled (loose bond)

Valence electron becomes free and they contribute to material’s conductivity

Question 18

Van Der Waals bond

Answer 18

The weakest of all chemical bonds

Dipoles, gases (gaseous materials at room temperature)

Question 19

Unit cell

Answer 19

A representative of the entire lattice and is repeated throughout the crystal