Modern Atomic Model
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Sometimes called:
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Crash Course: History of Atomic Theory (9:45)
https://www.youtube.com/watch?v=thnDxFdkzZs
Charge Cloud Model
Wave Mechanical Model
Orbital Model
Quantum Theory
How is it Different from the
Planetary Model?
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We can’t tell exactly
where an electron is!!
Heisenberg’s Uncertainty
Principle:
We can’t know exact
location and momentum
of an electron at the
same time.
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Electrons exist in
“orbital clouds”
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Denser the cloud
region the higher the
probability of finding
an electron there.
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Can’t tell exactly where an
electron is, but can tell
region of higher probability
of finding it.
Extra Videos
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Quantum Mechanics and the Bohr Model (6 minutes)
http://www.youtube.com/watch?v=-YYBCNQnYNM
Developing Modern Atomic Theory (6min)
Rutherford to Bohr to the Modern Model
http://youtu.be/45KGS1Ro-sc
The Uncertainty Principle (6min) Honors
Probability & Chance of Finding an e- and Orbital Shapes
http://www.youtube.com/watch?v=Fw6dI7cguCg
How are Electrons Organized?
Energy Levels
Sublevels
Orbitals
Spin
The Electron Hotel
Energy Levels (1-7)
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Electrons exist at different distances from
the nucleus.
 Energy
1
Levels
2 3
Lowest energy
Closest to nucleus
4
5
6
7
Highest energy
Farthest from Nucleus
Sublevels (s, p, d, f)
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Energy levels have certain number of sublevels.
Energy Level Sublevels Possible
1
s
2
s, p
3
s, p, d
4
s, p, d, f
5
s, p, d, f, (g)
6
s, p, d, f, (g, h)
7
s, p, d, f, (g, h, i)
Theoretical sublevels
Energy of Sublevels
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Sublevels have different levels of energy.
s
Lowest energy
p
d
f
Highest energy
Orbitals in
Sublevels
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Sublevels contain different numbers of orbitals.
Maximum 2 electrons can exist in an orbital.
Sublevel
s
p
d
f
# of Orbitals
1
3
5
7
Max e- in Sublevel
2 e6 e10 e14 e-
Aufbau Diagram
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Shows:
order of
electron filling
 order of
electron energy
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Follow the
“diagonal rule”
Writing Electron Configurations
 Let’s
write some electron
configurations!
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Ex: Magnesium
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Follow the diagonal rule
Overlap
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Some sublevels
“overlap”
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Results in certain
sublevels having
higher energy than
others
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Ex: 3d has higher
energy than 4s
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Electron Configurations for Atoms
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http://employees.oneonta.edu/viningwj/sims/atomic_electron_configurations_s1.html
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Extremely Corny Song About Electron Configurations
http://www.youtube.com/watch?v=Vb6kAxwSWgU&safe=active
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Electron Spin
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Electrons in an orbital spin
in opposite directions
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Pauli Exclusion Principle:
In order for two electrons to
occupy the same orbital, they
must have opposite spins.
Otherwise they
create a magnetic
field!
Orbital Diagrams
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Show electrons in individual orbitals
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s = 1 orbital, p = 3 orbitals, d = 5 orbitals, f = 7 orbitals
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“Hund’s Rule for Orbital Filling”
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When filling orbitals in a sublevel, place one electron in
each orbital before adding the second.
Paramagnetic vs.
Diamagnetic
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Diamagnetic: only paired electrons
in orbitals
Paramagnetic: at least one orbital
with an unpaired electron.
Diamagnetic atoms repel magnetic fields.
The unpaired electrons of paramagnetic atoms
realign in response to external magnetic fields and
are therefore attracted. Paramagnets do not retain
magnetization in the absence of a magnetic field,
because thermal motion randomizes the spin
orientations.
http://employees.oneonta.edu/viningwj/sims/electron_configurati
ons_t2.html
Shapes of Orbitals
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Orbitals come in different shapes and sizes.
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Region of highest probability of finding an
electron.
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Orbitals Shape & Energy & Spectral Line
http://www.youtube.com/watch?v=fKYso97eJs4
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s Orbital
Probability cloud has a spherical shape
p Orbitals (px, py, pz)
“Dumbell”
shape
Three p orbitals can
exist, on the x, y, z
axis in space
Clouds and Probability
d Orbitals
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Five possible d orbitals exist
f Orbitals
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Seven possible f orbitals exist
Valence Electrons
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Usually found in the s and p sublevels of
highest occupied energy level.
How many valence electrons?
 Draw a Lewis Dot Diagram of this element.
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1s22s22p63s23p64s23d104p2
Kernel
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All electrons except the valence
How many kernel electrons?
 How many valence?
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 1s22s22p63s23p3
Excited vs.
Ground State
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Ground State:
Electron configuration you would normally write
by following the order of filling
 Lowest to highest energy.
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Excited State:
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one or more electrons have jumped up to a
higher energy level.
Ex: 1s22s22p63s23p54s23d104p3
Atom vs. Ion Configurations
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Ions: atoms that have gained or lost electrons.
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Figure out how many electrons the ion has
then write configuration.
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Ex: 20Ca+2 has 18 electrons
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1s22s22p63s23p6 = 18 electrons
Electron Configurations for Ions
http://employees.oneonta.edu/viningwj/sims/atomic_electron_configurations_s2.html
DONE!
Impossible Configurations
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Break the rules.
Ex: 1s22s22p63s22d103p64s23d104p2
Ex: 1s22s32p63s23p6
s, p, d, f, “Blocks”
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Indicates what sublevel is being filled last
in the atom
Some Exceptions to Orbital Filling
(HONORS)
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When d and f sublevels get filled near the end of a
configuration we sometimes see exceptions.
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It is more stable for the orbitals of the d and f
sublevels to be half filled or filled completely than
to be one shy.
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Electrons from the sublevel below get “promoted”
up to make the atom more stable
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Ex: Copper
Crash Course Chemistry: The Electron
(13 minutes)
 http://www.youtube.com/watch?v=rcKilE9
CdaA
Quantum Numbers (Honors)
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Set of 4 numbers that help to describe most
probable location of each of an atom’s electrons.
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Principal Quantum Number: (n)
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describes principle energy level electron is in
values n = 1, 2, 3, ...7
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n=2 can describe the 8 electrons in 2nd energy level
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Azimuthal Quantum Number: (ℓ)
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Describes sublevel electron is in (s, p, d, f)
Values of (ℓ) range from: 0 to (n-1)
Ex:
If n=4
If n=2
ℓ can be 0, 1, 2, 3 (representing s, p, d, f sublevels)
ℓ can be 0, 1 (representing s, p sublevels)
n=2
n=3
ℓ = 1 means the electrons in 2”p”
ℓ = 2 means the electrons in 3 “d”
Magnetic Quantum Number: (mℓ)
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Describes the orbital the electron is in on sublevel
 Relates to it’s general orientation in space
Values from (-ℓ….0….+ℓ) **note the middle orbital is ZERO
Number of possible m values within a sublevel is = to the
number of orbitals within a sublevel
Ex:
ℓ= 1 (p sublevel),
Ex:
n= 3, ℓ= 2, mℓ= -1
(describes the 2 electrons in the 2nd orbital in 3d)
mℓ= -1, 0, +1
(representing px, py, pz orbitals)
Spin Quantum Number: (ms )
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Values of +1/2 or -1/2 (arrow up or arrow down)
1st electron in orbital is “clockwise” = +1/2
2nd electron in orbital is “counterclockwise” = -1/2
Ex: n=2, ℓ = 1, mℓ = +1, ms = -1/2
Represents 2p6 electron