Transcript HNRS 227 Lecture #2 Chapters 2 and 3

HNRS 227 Lecture #9
Chapter 9
Atomic Structure
presented by Prof. Geller
24 September 2002
Overview of Chapter 9
Atoms and atomic structure
The Bohr Model
Atomic Spectra
Quantum Mechanics
Electron Configurations
Quarks
Atoms and Atomic Structure
Atoms
“smallest” unit of matter
Nucleus
protons (positively charged)
neutrons (neutral)
Electrons orbit nucleus
negatively charged
Kirchoff’s Spectral Laws
Kirchoff’s Spectral Laws (empirical)
Continuous Spectrum
what produces them?
Emission Spectrum
what produces them?
Absorption Spectrum
what produces them?
Kirchoff’s First Spectral Law
Any hot body produces a continuous
spectrum
if it’s hot enough it looks something like this
digitally like this
Intensity
Wavelength
Kirchoff’s Second
Spectral Law
Any gas to which energy is applied, either
as heat or a high voltage, will produce an
emission line spectrum like this
or digitally like this
Intensity
Wavelength
Kirchoff’s Third
Spectral Law
Any gas placed between a continuous
spectrum source and the observer will
produce a absorption line spectrum like this
or digitally like this
Intensity
Wavelength
The Photoelectric Effect
A prelude to the Bohr atom
experiment explained by Einstein, but
performed by others
what caused this strange result?
Prelude to Bohr
Einstein used Planck’s quantized
particles
energy of photon is related to
frequency of light, not intensity
need high enough frequency to get
electrons released from metallic
surface
•E = h f
Bohr’s Atom - Atomic Spectra
Best described the workings of the
Hydrogen atom
one proton and one electron “around”
the proton moving in orbits that are
discretized (quantized) so that no
intermediate orbits are allowed
Absorption
Emission
Quantum Mechanics and
Duality of matter
act as waves or particles
Matter waves
De Broglie
l = h / m*v
Electron Configurations
Atomic number = number of protons =
number of electrons
Pauli Exclusion Principle
no two electrons in an atom can have the
same 4 quantum numbers
energy level, sublevel, orientation, spin
Heisenberg Uncertainty Principle
can’t precisely measure both position and
momentum
Quarks
Too many subatomic particles
could there be smaller particles
Protons and neutrons consist of
quarks
have partial charges
• 1/3 and 2/3
Leptons - light particles like electrons
Hadrons - heavy particles like protons
made up of quarks