Quantum Theory
-based partly on Heisenberg’s
Uncertainty Principle
the position and the
momentum of a moving
object cannot simultaneously
be measured and known
exactly
there is an inherent limitation
to knowing both where a
particle is at a particular
moment and how it is moving
in order to predict where it
will be in the future


Hesisenberg Uncertainty Principle
-an electron is in an electron orbital– probability space where an electron can be
found a certain percentage of the time as defined by Schrodinger’s
equations
-An orbital can hold 2 electrons (this means the bigger the energy level, the
more orbitals it has!).
-Schrodinger’s equations (once all the mathematics has been done) describe
where a particular electron is likely to be found
So, what do we know about where
electrons are found in an atom???
Type of
information
Energy Level
Sublevel
Labe What it represents
l
Distance from the
n
nucleus
l
Shape of Orbitals
Magnetic
lm
Spin
ls
Orientation of
Orbital (which
direction it is
pointing)
How electron is
spinning
How many options?
n=1 through n=7
n = 1  1 sublevel (s)
n = 2  2 sublevels (s, p)
n = 3  3 sublevels (s, p, d)
n = 4  4 sublevels (s, p, d, f)
Depends on the number of
sublevels.
p-orbitals follow the x, y, and z axes
(one orbital per axis)
Up = + ½
Down = - ½
The spinning of electrons generates
an electric field.
How many e- can
it hold?
2n2
Level 1 = ______
Level 2 = ______
Level 3 = ______
Level 4 = ______
Level 5 = ______
(each orbital can
hold 2 electrons)
For 2 electrons to
occupy the same
orbital they must
have opposite
spin.
Shape of S- Orbitals
Shape of P-Orbitals
Shape of D- Orbitals
Quantum Theory Review:
1) According to the quantum theory, are
electrons particles, waves, or both?
2) What are the 4 quantum numbers, and what
do they describe?
Distribution of electrons around the
nucleus
Aufbau Principle
• Each electron occupies
the lowest energy
orbital
– i.e. Electrons are Lazy!
• All orbitals related to an
energy level are of equal
energy.
– i.e. The three 2p orbitals
are the same energy
level.
Hund’s Rule
• Single electrons with the same spin must
occupy each equal-energy orbital before
additional electrons with opposite spins can
occupy the same orbitals.
– i.e. Electrons are unfriendly!
Analogy: Seats on a bus
Hund’s Rule
Example
Pauli Exclusion Principle
• A maximum of two electrons
may occupy a single orbital, but
only if the electrons have
opposite spins.
• spin-- Electrons have an
associated “spin,” either one
way or the other, like a top.
• These spins are called “spin up”
and “spin down.”
Exceptions to filling order are copper, chromium
and some others- because half-filled shells are
more stable, so an atom may borrow an electron
from next s shell to half fill a lower energy level.
Correct or Incorrect?
Complete the following diagram for Magnesium.
How many electrons will a neutral atom of magnesium have? ____
If you were to summarize the information about Magnesium, how might you write it more simply?
HOMEWORK:
Complete “Practice- Orbital Notations &
Electron Configurations”
DUE TOMORROW!!!
Apartment Analogy: What description would go in the right column?
Apartment Rules
From the Bottom Up: Rooms must be filled from
the ground floor up. Fill the one room on the first
floor before starting to put new tenants on the
second floor. Then fill the s room before the p
rooms. At higher floors the order might change a
bit.
Singles First: the owner of the building wants to
have the tenants spread out as much as possible.
For that reason singles are placed in rooms before
couples. If couples must be placed into a room
then all of the other rooms on that floor must
already have a single in them.
Opposite Gender Only: When two people are
placed in a room they must be of opposite
genders. No men may room together and no
women may room together. This is an arbitrary
rule on the part of the owners: in a just world we
wouldn’t have to follow it. But quantum
mechanics has nothing to do with justice.
Electron Rules