Honors Chemistry
Chapter 5
Electrons
“The more success the quantum theory has, the sillier it looks.”
~Albert Einstein, Nobel Prize in Physics, 1921.
“If quantum mechanics has not yet profoundly shocked you, you have not
yet understood it.”
~Niels Bohr, Nobel Prize in Physics, 1922.
“Quantum mechanics: the dreams that stuff is made of.”
~unknown
Where are electrons located?
• Outside the nucleus
• How are they arranged?
Bohr model of electron
placement
 Called the “planetary” model
 Electrons closer to the nucleus –
lower “energy level”
 Electrons farther away from the
nucleus – higher “energy level”
 Called the “shells” K, L, M, N
 2, 8, 18, 32 electrons
 Studied the emission spectrum of
Hydrogen
 Specific colors that are emitted
(given off) when an atom releases
energy
Quantum Staircase
Niels Bohr
An electron in a stable orbit will
have a specific, restricted
(quantitized) energy:
Max Planck
• Stated that the object (metal)
emits energy in small,
specific amounts called
Quanta.
• Quantum is the minimum
quantity of energy that can
be lost or gained by an atom.
• Step ladder analogy
Albert Einstein
 Took Planck’s idea a little
further.
 He introduced that
electromagnetic radiation has a
dual wave-particle nature.
 Light exhibits many wavelike
properties
 Can also be thought of as a
stream of particles
Bohr’s Model
• Two important concepts from
Bohr:
• Electrons exist only in
certain discrete energy
levels
• Energy is involved in
moving an electron from
one level to another
• IN REALITY, ELECTRONS DO
NOT ORBIT THE NUCLEUS
LIKE PLANETS ORBITING A
STAR!!!!
• Electrons not really in “planetary”
orbits
• Are really in areas of “probability”
called “electron clouds”
• Quantum Model of electron
placement
Quantum Mechanical
Model
• This model determines the
allowed energies an electron
can have and how likely it is to
find the electron in various
locations around the nucleus
• Heisenburg’s Uncertainty Principle
– it is not possible to know both the
velocity and position of a particle at
the same time
– velocity = speed and direction

Orbital - 3 dimensional region
around the nucleus where a
particular electron can be located
“clouds” - that show a region of
high probability of finding an
electron
 size and shape of “cloud” depends
on energies of electrons that
occupy them

Principal Energy Levels
Indicates main energy
level of an electron in an
atom
 called “shells”
 1 = lowest
7 = highest
 can be any positive
integer

Sublevel
• Indicates the shape of an
orbital
labeled s, p, d, f
s
= sphere
p = dumbbell or figure-eight
d = 4 lobes
f = complicated
• Orbital shapes for Sc
• funky orbitals
Principal Energy Levels
 Are
divided into sublevels
 the number of sublevels allowed is
equal to the principal energy level (n)
(up to n=4)
 PEL = 1
1 sublevel
 PEL = 2
2 sublevels
 PEL = 3
3 sublevels
 PEL = 4
4 sublevels
Wish you were here?
Well, you’re not, so pay attention!
“s” sublevel – 1 orbital allowed
 “p” sublevel – 3 orbitals allowed
 “d” sublevel – 5 orbitals allowed
 “f” sublevel – 7 orbitals allowed


PEL
1
2
3
4
sublevels allowed
s
s, p
s, p, d
s, p, d, f
Each sublevel has a certain number
of orbitals allowed
Sublevel
s
p
d
f
orbitals allowed
1
3
5
7
• Maximum of 2 e- in any
orbital !
• They “spin” in opposite
directions
WAKE UP!!!!!!!!
Don’t give up!
You can’t escape!
I know you’d rather be here,
but it gets better, I promise!
Are you ready????????
• Chart that follows this slide:
• Principal energy level
• type of sublevel
• #orbitals per type
• #orbitals per level
• Max. # electrons
Principal
Energy Level
(pel)
Type of
sublevel
# orbitals per
type of
sublevel
# orbitals per
pel
n2
Maximum
number of
electrons per
pel
2n2
1
s
1
1
2
2
s
p
1
3
4
8
s
p
d
s
p
d
f
1
3
5
1
3
5
7
9
18
16
32
3
4
Rules for writing electron
configurations
• Add one electron at a time according to
these rules:
• 1. each added electron is placed in a
sublevel of lowest energy available
(Aufbau Process)
• 2. No more than 2 electrons can be placed
in any orbital (Pauli Exclusion Principle)
• 3. Before a second electron can be placed
in any orbital, all the orbitals of the
sublevel must contain at least one electron
(Hund’s Rule)
• 4. No more than 4 orbitals are occupied in
the outermost principal energy level of any
atom. (next electron must enter the next
principal energy level)
NOW!!!!
• We will start writing electron configurations
•
“Regular” and
• “Exceptions”
• Stanford explanation
 Atoms
absorb a SPECIFIC amount of
energy – quanta
 Electrons “jump” up into energy
levels where they really don’t belong
 Immediately drop back and release
that specific amount of energy in the
form of light of specific wavelength
and frequency (color)
Spectroscopy
 Used
to study structure of atoms
 substances heated
– e- move to higher energy levels
– “fall back” - release photons of
energy of specific wavelength
 produce
lines”
a series of “spectral
– are characteristic to specific
substances
– used as an identifying tool
Ground state atom where the
electrons are in the
lowest available
energy levels
 excited state atom has electrons
that have
“jumped” to higher
energy levels

• Can identify elements by
the colors they produce
• FIREWORKS!!!
• Flame tests – lab we will
do
• flame test lab!