Catalyst
Name the following compounds or write the formulas:
1. CuSO4
2. N2Cl6
3. Iron (II) Phosphate
4. Copper (III) Nitrate
5. Hydrochloric acid
Reading Guide for Unit 1
• You should be able to answer all the essential questions
for all sections in Chapters 6 and 7.
• Let these guide your note taking (have them be the
questions you put on the left side of your Cornell Notes!)
• Homework is due the day of the Unit 1 Exam
• Don’t forget to read the Princeton Review book!
Thoughts on the Quiz
• Sig Figs – We got this
• Dimensional Analysis – Memorize your metric
conversions!
• Naming Compounds – Yikes…
LECTURE 1.4 –
QUANTUM HISTORY
Today’s Learning Targets
• 1.1 – I can discuss the dual nature of light. Using the
speed of light, I can calculate the frequency and the
wavelength of a beam of light.
• 1.2 – I can explain the development of the quantum
mechanical model incorporating the
contributions/experiments of Plank, Einstein, Bohr, de
Broglie, Heisenberg, and Schrödinger.
Electromagnetic Radiation
• Visible light is a type of electromagnetic radiation
• Electromagnetic radiation is made up of:
• Radio Waves, Microwaves, Infrared, Visible Light, Ultraviolet light,
X-Rays, and Gamma Rays
• All EM waves move at 3.0 x 108 m/s
Electromagnetic
Wave!
Important Parts of a Wave
• Wavelength – Distance between two adjacent peeks
• Crest – Highest point of wave
• Trough – Lowest point of wave
• Frequency – Number of cycles per given period of time
Calculating Wavelength and Frequency
• c = Speed of light (always 3.0 x 108 m/s)
• λ = Wavelength
• ν = Frequency (in s-1 or Hz)
c = ln
Class Example
• A laser used in eye surgery to fuse detached retinas
produces radiation with a frequency of 4.69 x 1014 s-1.
What is the wavelength of the radiation?
Table Talk
• A yellow light given off by a sodium vapor lamp used for
public lighting has a wavelength of 589 nm. What is the
frequency of the radiation?
The Atom
Problems with the Current Model
• There are 3 atomic experiments that challenged the wave
theory of light:
(1) Blackbody Radiation
(2) The Photoelectric Effect
(3) Hydrogen Emission Spectrum
Problem #1: Blackbody Radiation
• When objects heat up they go
through the spectrum of colors
• PROBLEM – Classical physics
could not explain the relationship
using the idea of energy as a
continuous spectrum.
Plank’s Solution
• Plank proposed that energy must be gained or lost in
specific chunks.
• Energy is quantized and can only be gained or lost in
specific amounts
E = hu
• E = Energy (in J)
• h = Plank’s constant (6.626 x 10-34 J · s)
• v = Frequency
Quantized Energy – Think of It Like a
Staircase!
Problem #2: Photoelectric Effect
• When light of a certain intensity was shined on a metal,
electrons were emitted.
• This was not consistent with the theory that light was
a wave, rather it seemed light was acting like a
particle
Einstein’s Solution
• Einstein said that light was behaving as a stream of tiny
particles. He called these photons.
• Therefore, the energy of these photons must be:
E photon = hu
Einstein’s Solution
• Because of Einstein’s conclusion, we now view light as
being both a wave and a particle at the same time.
• Known as the duality of light
Quick Talk
• Find a partner near you. One partner, explain blackbody
radiation and Plank’s solution to this problem.
• The other partner, explain the photoelectric effect and
Einstein’s solution.
Problem #3: Atomic Emission Spectrums
• When a gaseous element is excited, a color is observed.
• The wavelengths being emitted can be detected.
• A spectrum is not detected, only 4 specific wavelengths
Bohr’s Solution
• Since only specific wavelengths
are observed, he concluded that
electrons had specific energy
levels.
• Bohr proposed that electrons
moved in circular orbits around
the nucleus at certain “allowed”
energy states.
Energy of Each Orbit
• Bohr created an equation to
predict the energy of the
electron at each energy level:
1
E = (-2.18×10 J)( 2 )
n
-18
• E = Energy (in Joules)
• n = Energy level (must be
whole numbers)
Bohr’s Equation Fits the Emission
Spectrum
• The spectrum that was observed for hydrogen occurred
when electrons went from a high energy state to a low
energy state.
• We can calculate the energy transition using Bohr’s
equation:
1 1
DE = (-2.18×10 J)( 2 - 2 )
n f ni
hc
1 1
-18
hu = = (-2.18×10 J)( 2 - 2 )
l
n f ni
-18
White Board Practice
• On the white board, complete the problem that you have
been assigned.
• Once everyone at the table has completed the problem,
explain to your group how you solved the problem.
• Repeat until all problems are completed.
5 Minute Break
de Broglie’s Matter Waves
• If light can have particle properties, why can’t particles
have wave properties?
• Louis de Broglie proposed that all mater has a
wavelength and this wavelength can be calculated by:
• h = Plank’s constant
• m = mass
• v = velocity
• λ = wavelength
h
l=
mv
de Broglie Matter Waves
• Matter waves only observed for substances that have
extremely small masses.
Heisenberg’s Uncertainty Principle
• If electrons behave like waves, then we have some new
problems to consider.
• We cannot know both the momentum and place of an
object at any particular instant.
• Only important for very small objects (like electrons!).
• We cannot know the precise location of the electron,
rather we only know areas where there is a high
probability of finding an electron.
J – TPS
• Why does the Heisenberg evidence against the Bohr
model of the atom that places electrons in orbits?
Probability of Finding You
Schrödinger
• Schrödinger incorporated the dual nature of the electron
into one equation.
• Solving the Schrödinger equation give’s us ψ2 values that
tell us the probability of finding an electron.
• The solutions to the Schrödinger equation give us orbitals
of different shapes and probability densities.
Equations Seen on Past AP Exams
c = ln
E = hu
1
E = (-2.18×10 J)( 2 )
n
-18
h
l=
mv
Has been seen,
but very rarely
Quantum History
• With your table create a timeline of the development of
the quantum mechanical model. Make sure to include:
• Plank’s quantized energy (1900)
• Einstein’s photoelectric effect (1905)
• Bohr’s atomic model (1913)
• de Broglie’s matter waves (1924)
• Heisenberg’s Uncertainty Principle (1925)
• Schrödinger’s mechanical wave model of the atom (1926)
• Be sure to include a description of the discovery, any
necessary equations, and the importance of this discovery
Closing Time
• You should read sections 6.1 – 6.5 and answer the
corresponding questions in the book to stay on pace.
• Post-lab for Lab 1 due on Wednesday.