Exam #1

Question 1

Classical Physics

Answer 1

Inadequately describe the interaction of light with matter (Ex. photoelectric effect, blackbody radiation, atom line spectra, and electron diffraction)

Question 2

Constructive interference

Answer 2

wave1 and wave2 have same max and min positions so amplitude doubles

Question 3

Increase of energy relies on an increase of

Answer 3

frequency

Question 4

Planck

Answer 4

atoms & molecules can emit energy in discrete quantities (aka energy levels)

Question 5

Photoelectric Effect

Answer 5

• Electrons are ejected from surface of certain metals exposed to electromagnetic radiation
• Helped disprove classical physics
• Number of electrons ejected was proportionate to intensity of light
• No electrons would eject if frequency of light is lower than threshold
• KE of ejected electrons is proportional to the difference between the frequency of the light and threshold frequency
• Supported the idea that light possesses both particle & wave like properties
  E=hv=KE+Phi where phi is the work function aka threshold

Question 6

Emission Spectra of Atoms

Answer 6

• Evidence of energy quantization of matter
• a spectrum of the electromagnetic radiation emitted by a source
• Atoms may only transfer energy in the form of electromagnetic radiation at certain values which depend on the identity of the element

Question 7

The De Broglie Hypothesis

Answer 7

if light behaved like a stream of particles, then particles could possess wavelike properties (the particle in motion can be treated like a wave (aka exhibit momentum))

Question 8

The Heisenberg Uncertainty Principle

Answer 8

Impossible to know simultaneously the momentum (p)) and the position of the particle (x) with certainty

Question 9

Schrodinger Wave Equation

Answer 9

• The complete information about the state of a quantum particle was contained in a wave function (a function of the position of the particle; related to the probability of finding the particle in a specific region of space)
• Most conveniently solved in spherical polar coordinates (r, theta, phi) (also goes with three quantum numbers)

Question 10

To describe a physical system, the wavefunction must:

Answer 10

• have a single value at all points
• total area under wave function^2 must be equal to unity; integral of wave function^2 equal one
• wave function must be continuous

Question 11

particle in a box model

Answer 11

• PE is zero in box and infinity out of box
• E in box is entirely KE
• Described as having “free particles” “conjugated” “no interaction”
• Uses E= n^2h^2 / 8mL^2
  Demonstrates:
• Lowest energy level is not zero (ground state E= h^2 / 8mL^2)
• Wavefunction describes the wave behavior of the particle
• Energy level get further apart as energy levels increase (aka spacing between energy levels is inversely proportional to both m and L^2)
• Quantization of energy levels of a system is a direct result of the localization of the particle in a finite region of space

Question 12

Hydrogen Energy Levels

Answer 12

• Energy levels get closer together as they increase
• “not free” “hydrogen-like atom” “aotm” “atomic system with charges”
• Uses Rydberg equation: E= Rh(1/n^2 - 1/n^2)

Question 13

Schrodinger equation (Hydrogen)

Answer 13

Exactly solvable

Question 14

Quantum numbers & Energy Equation

Answer 14

1) Principle number: n=1,2,3 (determines energy of electron)
2) Angular momentum: L=0,1,2,n-1 (determines shape of orbital)
3) Magnetic: ML= -1,0,1 (plus or minus of L) (determines orientation in space)
E= -Z^2E^4m / 8h^2Eo^2n^2
- Equation shows that energy only depends on n
- Fourth quantum number Ms determines spin of electron

Question 15

Electron wavefunction (atomic orbitals) given by wavefuntion(nLm) (r, theta, phi)

Answer 15

Rnl (r) Wave Function lm (theta, phi)
where r is the radial part of wavefunction and theta & phi are the angular functions

Question 16

Bohr Model

Answer 16

Correct: Electrons have certain energies & orbitals are quantized
Wrong: Circular orbit (aka big bang theory logo)

Question 17

Light Spectrums

Answer 17

Infrared: lower energy (longer wavelength)
Visible Light: Wavelengths 350-800nm
UV: higher energy (shorter wavelengths)

Question 18

Graphing the energy levels and wave functions on V(r) (y-axis) and R (x-axis)

Answer 18

• V(r) is the potential energy between electron and nucleus
• Energy levels get closer as they increase (H energy levels) and then each energy level shows wavefunction where # of nodes is equal to n-1

Question 19

Wavefunction

Answer 19

• Describes the wave behavior of the particles
• Sign of orbital matters for bonding orbitals
• Squaring it can tell about the probability of position
• Where wave function goes to zero, electron will not be found there
• a function of the position of the particle; related to the probability of finding the particle in a specific region of space

Question 20

Uncertainty equation (finding the % uncertainty)

Answer 20

uncertain position over precise position equal uncertainty
()p/p (100)=% where p can be found by mass times velocity (mu)