Lecture notes: CHEM103 Fall 2008 – September 23
1) BRIEF exam overview
2) Review: atoms/moles/mass conversions
BIG PICTURE: UNDERSTAND ELECTRONS BECAUSE THEY DETERMINE REACTIVITY
3) Energy concepts
a) transfer of energy between forms – CONSERVATION!
b) directionality of energy transfer between frames
c) energy & “stability” – opposites attract
4) LIGHT INTERACTS WITH MATTER (YES – ELECTRONS!)
a) Light as a wave
i) Electromagnetic (light) spectrum
ii) Conversions between wavelength & frequency
b) Light as a particle
i) Planck blackbody radiation
ii) Conversions between photon frequency and energy
5) Photoelectron effect: Einstein’s interpretation
* can also be: ions, electrons, molecules, albatrosses, etc…
I. In 75 minutes of lecture, your body consumes 11.9 moles of oxygen gas.
1) WHAT MASS (IN g) OF OXYGEN IS THIS? 2) HOW MANY ATOMS OF OXYGEN DID YOU USE?
II. Oxygen is carried in blood by hemoglobin, bound to iron atoms within the molecule.
If a typical person has 5 liters of blood, and in that blood, a typical person has about 46mg/dL of iron.
1) HOW MUCH IRON (in moles) DOES PERSON’S BLOOD CONTAIN? 2) HOW MANY ATOMS DOES THIS REPRESENT?
CHAPTER 7 – LIGHT AND MATTER: THE ELECTRONIC STRUCTURE OF THE ATOM
WHERE ARE WE NOW?
BUT WHAT ABOUT THE ELECTRONS?
HOW ARE THEY DISTRIBUTED AROUND THE ATOM???
NOT REALLY – THEY ARE DESCRIBED IN TERMS OF ENERGY, NOT OF POSITION!
GOAL: UNDERSTAND THE NATURE OF ELECTRONS
HOW? BY THE INTERACTIONS OF LIGHT WITH MATTER
Digression: how do particles and waves behave differently?
1) light can be described as a WAVE: using the concepts of wavelength & frequency
(“nu” – units of 1/seconds OR “Hz”)
c = l × n (speed = wavelength x frequency)
(lambda – units of length)
DON’T confuse wavelength and frequency with AMPLITUDE (or intensity)
SOUND EXAMPLE: What is the wavelength of a low-pitched sound wave?
frequency = 75 Hz (sec-1)
given: speed = 340 m/s (speed of sound at sea level)
(application: placing speakers in a room; locating low pitches)
NOW WITH LIGHT: What is the frequency of the light from a red laser pointer?
wavelength = 660 nm
speed = 3.00 x 108 m/sec (speed of light in a vacuum)