Download 4.2 Quantum Model File

Ch. 4.2
Quantum Model of the Atom
POINT > Recall Bohr’s atomic model
POINT > Identify electrons as wave-like particles
POINT > Define Heisenberg’s uncertainty principle
POINT > Describe electron orbitals as three
dimensional probabilities
POINT > Describe how quantum numbers define
electron orbitals
POINT > Recall Bohr’s atomic model
Problem:
Bohr’s model
worked for
hydrogen, but
was inaccurate
with atoms
having more
than one
electron
Bohr
POINT > Identify electrons as wave-like particles
Light has wave-like properties
Louis de Broglie showed that electrons
also have wave-like properties
de Broglie showed that electrons undergo
diffraction and interference like waves (see p 98-99)
POINT > Describe Heisenberg’s uncertainty principle
Heisenberg’s uncertainty principle: It is impossible
to know the position and velocity of an electron
Any attempt to locate an electron alters its path
This is true for any atomic particle or photon
WB CHECK:
What did de Broglie discover about electrons?
a)
b)
c)
d)
electrons only exist at discrete energy levels
the location and velocity of electrons is uncertain
electrons undergo diffraction and interference
electrons have a much smaller mass than protons
WB CHECK:
What did Heisenberg tell us about electrons?
a)
b)
c)
d)
electrons only exist at discrete energy levels
the location and velocity of electrons is uncertain
electrons undergo diffraction and interference
electrons have a much smaller mass than protons
POINT > Describe electron orbitals as
three dimensional probabilities
Erwin Shrödinger used mathematical
models to describe electron motion
Electrons are restricted to certain energy levels
(supported Bohr)
Electrons do not follow specific paths (unlike
Bohr model)
POINT > Describe electron orbitals as
three dimensional probabilities
Shrödinger’s equations were the
foundation of quantum theory
The location of an electron is described as a
mathematical probability in space
The result is the electron cloud model of the atom
POINT > Describe electron orbitals as three
dimensional probabilities
Electron cloud model of the atom
Where the cloud is more dense, there is a higher
probability of finding an electron (Usually drawn
where electrons are ~90% of time)
WB CHECK:
Shrodinger’s equations
a) supported Bohr’s idea that electrons have discrete
energy levels
b) supported Bohr’s idea that electrons move on
specific paths
c) described electron orbitals as mathematical
probabilities
d) a and b
e) a and c
f) b and c
Quantum Mechanical
(Electron Cloud Model)
POINT > Describe electron orbitals as three dimensional
probabilities
The quantum model:
Describes energy levels an electron can have
Describes an atomic orbital as a region of space
with a high probability of finding an electron
POINT > Describe electron orbitals as three
dimensional probabilities
Homework:
Read pages 98-100
Pre-read pages 101-104
Atomic Spectra Lab Due next Friday