Electrons
• Bill Nye
• Sponge Bob element song
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
 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
• Electrons not really in “planetary”
orbits
• Are really in areas of “probability”
called “electron clouds”
• Quantum Model of electron
placement

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

WAKE UP!!!!!!!!
• 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
Wish you were here?
Well, you’re not, so pay attention!
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
Don’t give up!
You can’t escape!
I know you’d rather be here,
but it gets better, I promise!
Are you ready????????
“s” sublevel – 1 orbital allowed
 “p” sublevel – 3 orbitals allowed
 “d” sublevel – 5 orbitals allowed
 “f” sublevel – 7 orbitals allowed

Principal Energy Levels
 Are
divided into sublevels
 the number of sublevels allowed is
equal to the principal energy level (n)
 PEL = 1
1 sublevel
 PEL = 2
2 sublevels
 PEL = 3
3 sublevels
 PEL = 4
4 sublevels

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 !
• 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)