Download Atomic Structure

Unit 5 :
Atomic Structure
Dalton’s Atomic Theory(1803)
1) Elements are made up of tiny invisible
particles called atoms.
2) Atoms of the same element are identical.
Atoms of different elements are different.
3) Compounds are formed when atoms
combine. Each compound has a specific
number and kinds of atom.
4) Chemical reactions are rearrangement of
atoms. Atoms are not created, destroyed,
nor broken apart.
Experiments to determine what
an atom was
• J. J. Thomson- used Cathode ray tubes
• Clip of Cathode Ray Tube
Thomson’s Experiment
Voltage source
-
+
Thomson’s Experiment
Voltage source
-
+
Thomson’s Experiment
Voltage source
n
+
Passing an electric current makes a beam
appear to move from the negative to the
positive end.
Thomson’s Experiment
Voltage source
• By adding an electric field
Voltage source
+
n
By adding an electric field, he concluded
that the particles were
A.
B.
C.
D.
Positively charged
Negatively charged
Not charged
Some negative and some positively charged
Thomsom’s Model
• Found the electron.
• Couldn’t find positive (for a
while).
• Said the atom was like plum
pudding (p. 101) (or Jello
with fruit)
• A bunch of positive stuff,
with the electrons able to be
removed.
Spread out
+ charge
Rutherford’s Experiment
• Used _________to produce alpha particles.
• Aimed alpha particles at gold foil by
drilling hole in _______ container.
• Since the mass is evenly distributed in
gold atoms alpha particles should go
straight through.
• Used gold foil because it could be made
atoms thin.
Rutherford’s Experiment
• After watching video, label the parts of his setup on your handout.
Lead
block
Polonium
Florescent
Screen
Gold Foil
Alpha Particle
What he expected
Because
Because, he thought the positive charge
(and mass)was evenly distributed in the
atom. (according to Thomson’s Model)
What he got
How he explained it
• Atom is mostly empty
• Small dense,
positive piece
at center.
Rutherford just concluded
that atoms have:
A. Electrons
B. Protons
C. Neutrons
D. a Nucleus
+
How he explained it
• Atom is mostly empty
• Small dense,
positive piece
at center.
• Alpha particles
are deflected by
it if they get close
enough.
+
+
Modern View
• The atom is mostly
empty space.
• Two regions
• Nucleus- protons
and neutrons.
• Electron cloudregion where you
might find an
electron.
Sub-Division of an Atom
• Atom has two parts:
Electron Cloud - space
where electrons travel
Nucleus - small, dense
Center of atom
Size of Atoms
• Very small, drawing a line across a penny
would cross over _______________ atoms
• Diameter of 1 atom = 1x10-8 cm --or-A. 350,000
1 Angstrom
(Å)
B. 4 million
C. 63 million
-- or –
D. 810 million
10 nanometers
Size of Atoms
• Most of atom is electron cloud
• Nucleus is a very tiny portion of atom
• Ratio, If an atom were the size of a football
stadium, the nucleus would be the size of a
pea !
Sub-Atomic Particles
•
•
•
•
• ELECTRONS:
Negatively charged
Rotate around nucleus
All electrons are identical
Mass: insignificant compared to nucleus-0
Sub-Atomic Particles
•
•
•
•
•
•
• Protons:
Positively charged - same magnitude as eLocated in nucleus
Mass: “heavy” compared to an electron
All protons are identical
If proton were 1 kg, electron would be 1 cg
Mass = 1 atomic mass unit (amu)
Sub-Atomic Particles
•
•
•
•
•
• Neutrons:
Neutral - no charge
Located in nucleus
All neutrons are identical
Mass: same as proton ( 1 amu)
. Proton
Neutron Electron
1 amu
1 amu
0 amu
What the Numbers on Periodic Table
Tell us about the Atom
Atomic Number
 The number of Protons
 Equal to the number of
electrons if atom is
neutral
 Protons determine identity of
Element
 Number of Protons does not
change
1
H
1.0079
What the Numbers on Periodic Table
Tell us about the Atom
1
Atomic Mass
H
1.0079
Mass Number:
• The Mass of an Atom (NOT found on Pd Table)
• Mass of an atom = mass of the nucleus
• Determined by counting Protons & Neutrons
• Mass Number = # of Protons
Ex: Oxygen
+ # of Neutrons
Ex: Beryllium
# of protons =
8
+
# of neutrons = 8
# of protons =
4
+
# of neutrons = 5
Mass Number = 16
Mass Number =
9
Your Turn: Mass Number
Ex: Potassium
# of protons =
19
+
# of neutrons =
Mass Number =
40
Enter the # of neutrons into your clicker
Your Turn: Mass Number
Ex: Potassium
# of protons =
19
+
# of neutrons = 21
Mass Number =
40
More Examples
2O
Ex: Oxide (
)
Ex: Oxygen
# of protons =
# of electrons =
# of neutrons =
8
8
8
Mass Number = 16
# of protons =
# of electrons =
# of neutrons =
8
10
8
Mass Number = 16
How many neutrons and electrons ?
Your Turn: Number of Electrons
Ex: Bromide (Br-)
# of protons = 35
# of electrons =
# of neutrons =
Complete the Chart
Mass Number = 79
How many protons, then enter the # of
neutrons into your clicker?
Your Turn: Number of Electrons
Ex: Bromide (Br-)
# of protons = 35
# of electrons =
# of neutrons = 44
Mass Number = 79
Enter the # of electrons.
Your Turn: Number of Electrons
Ex: Bromide (Br-)
# of protons = 35
# of electrons = 36
# of neutrons = 44
Mass Number = 79
Your Turn: Number of Electrons
Ex: Magnesium (Mg+2)
# of protons = 12
# of electrons =
# of neutrons = 13
Complete the Chart
Mass Number = 25
Enter the # of neutrons in clicker
Your Turn: Number of Electrons
Ex: Magnesium (Mg+2)
# of protons = 12
# of electrons = 10
# of neutrons = 13
Mass Number = 25
Enter the # of electrons in clicker
Welcome Back !
1. Check Your Posted Grades
 Look at 2nd Marking Pd CLC’s and Verify Total
 Look at Separate CLC Gradesheet for 3rd MP
2. Pick up your “Clicker” and Log in.
3. Tell Your Lab Partner what “Mass Number” means
4. Enter in clicker the # of Neutrons that are in Mg-25
Welcome Back !
1. Have you or your partner Log in to a nearby
computer.
2. Ask your partner what “Atomic Number” means
3. Tell Your Lab Partner what “Mass Number” means
4. Enter in clicker the # of Neutrons that are in Mg-25
Warm-Up
Ex: Magnesium (Mg+2)
# of protons = 12
# of electrons = 10
# of neutrons = 13
Mass Number = 25
Enter the # of electrons in clicker
Lesson Review
1. The _____ is the total mass of a single
atom.
A.
B.
C.
D.
Atomic Mass
Mass Number
Atomic Number
Number of Protons
Lesson Review
2. The _____ is always equal to the number
of protons.
A.
B.
C.
D.
Atomic Mass
Mass Number
Atomic Number
Number of Neutrons
Lesson Review
3. The _____ is equal to the number of
protons and neutrons
A.
B.
C.
D.
Atomic Mass
Mass Number
Atomic Number
Number of Protons
Lesson Review
4. The _____ is the difference between the
number of protons and the number of
electrons
A.
B.
C.
D.
Number of Neutrons
Atomic Number
Mass Number
Charge
Time for Practice:
• Log in to Moodle and go to the pHet
Activity called “Build an Atom”
• Choose Game at Level 4
Isotopes
• Different “Varieties” of an Atom
• Isotopes are atoms of the same element, but
with different #’s of Neutrons. Therefore,
they have different Mass #’s.
• Isotopes are Chemically Identical
• About 300 Stable Isotopes of the first 83
elements exist, plus several hundred more
unstable isotopes
Isotopes of Hydrogen:
WhatWhat
has to
be
the
same
for
all
will be different?
three?
1 proton
0 neutrons
Mass #: 1 amu
1 proton
1 neutron
2 amu’s
1 proton
2 neutrons
3 amu’s
Isotopes of
Have you ever heard
Hydrogen:
of “tritium” before?
Hydrogen-1
Hydrogen-2
“Protium”
“Deuterium”
Mass Number
1 proton
0 neutrons
Mass #: 1 amu
1 proton
1 neutrons
2 amu’s
Hydrogen-3
“Tritium”
1 proton
2 neutrons
3 amu’s
Isotopes of Hydrogen:
Hydrogen-1
“Protium”
Hydrogen-2
“Deuterium”
1 proton
0 neutrons
Mass #: 1 amu
1 proton
1 neutrons
2 amu’s
Hydrogen-3
“Tritium”
1 proton
2 neutrons
3 amu’s
Naming Isotopes
• The hydrogen isotope with 0 neutrons can
be written as hydrogen-1 or 1H
Mass Number
14
6
Number of Protons
C
How many
Neutrons?
Your Turn: Writing Isotopes
How many of each particle are in this
isotope:
A
48 protons
51 electrons
124 neutrons
B
51 protons
48 electrons
73 neutrons
C
51 protons
51 electrons
124 neutrons
124
51
-3
Sb
D
51 protons
54 electrons
73 neutrons
Your Turn: Writing Isotopes
•
•
•
•
The following element has how many
51 protons
______
54 electrons
______
______
73 neutrons
124
-3
51
Sb
Atomic Mass
1. Time for Grade Check
2. Look at your grade sheet and Calculate the
Average of your grades for each unit
1. Is this your actual grade?
3. Grade = Unit1*(Weight) + Unit2*(Weight)….
Atomic Mass
1. Use this formula to calculate grade
2. Grade = Unit1*(Weight) + Unit2*(Weight)….
Atomic Mass
• The AVERAGE mass of an atom of that
element
• Weighted according to the abundance of
each Isotope
• Ex: Football team
Abundance of Hydrogen Isotopes:
Hydrogen-1
“Protium”
Hydrogen-2
“Deuterium”
Hydrogen-3
“Tritium”
Mass = 1 amu
Mass = 2 amu
Mass = 3 amu
99.985%
0.015%
1 x 10-16%
Average Mass = 1.0079 amu = Atomic Mass
Atomic Mass
• The AVERAGE mass of an atom of that
element
• Weighted according to the abundance of
each Isotope
• Ex: Football team
• Why are 99% of hydrogen atoms H-1?
Pre-Knowledge Check
• Get out your Atomic Structure Pre-Quiz and
correct any incorrect answers you might
have
Alert:
“ScienceStability
Sense”
Nuclear
is Tingling
• Rutherford says that nucleus is incredibly dense
and small.
• We now know that the nucleus consists of a
bunch of individual protons
• Nucleus consists of a bunch of protons crammed
together in a tiny area
Nuclear Stability
• Protons Repel other protons.
+
+ +
• Putting Protons together in a tiny nucleus is
unstable because of this repulsion
• Neutrons act as “glue” to hold the protons
together in the nucleus
Stable
Ratio of Neutrons to Protons
• For smaller elements (1-30), about 1
neutron per proton seems to work best
• 1:1 ratio
Ex: Oxygen
Protons = 8
Neutrons = 8
Most Stable Isotope
has 1:1 Ratio
Ex: Beryllium
Protons = 4
Neutrons = 5
Most Stable Isotope
has close to 1:1 Ratio
Alert:
“ScienceStability
Sense”
Nuclear
is Tingling
• Therefore, without this proper ratio of neutrons,
the nucleus would be unstable and fly apart.
So how can Hydrogen-1 exist as a stable atom?
Ratio of Neutrons to Proton
• As the elements get larger (>30), a higher
ratio of neutrons is needed.
• Example: Mercury has 80 protons, but
around 120 neutrons are needed to hold
them together
• 120 / 80 is a 1.5 : 1 ratio.
Your Turn: Predicting Stability
1. Who would more likely be stable?
A.
B.
C.
D.
Phosphorous – 15
Phosphorous – 31
Phosphorous – 44
Phosphorous – 58
Protons
15
15
15
15
Neutrons
0
16
29
43
Your Turn: Predicting Stability
2. Who would more likely be stable?
Protons Neutrons
0
74
A. 74W
74
76
B. 150W
110
74
C. 184W
74
151
D. 225W
Radioactivity
• After element # 83, the repulsive force of so
many protons is so strong that no amount of
neutrons will hold nucleus together permanently
• Thus, no stable isotopes exist for these elements
• These elements are called radioactive elements
•
The nucleus breaks apart and pieces of
radiation come flying out
Types of Radioactive Decay
• Alpha Particle (α) – positively charged
• Beta Particle (β) - negatively charged
• Gamma Radiation (γ)- no charge
Alpha (α ) Decay
240
Pu
94
236
U
92
+
4
He
2
Your Turn: Alpha Decay
• Write down your description of what
happens during alpha decay
Beta (β ) Decay
228
Ra
88
228
Ac
89
+
0
e
-1
Your Turn: Beta Decay
• Write down your description of what
happens during beta decay
Gamma (γ ) Radiation
• Gamma Radiation is NOT a particle
• It is Electromagnetic Radiation given off
during Alpha or Beta Decay
Your Turn: Decay Equations
• Write an equation of the alpha decay of Polonium-214
214
84 Po
210
82 Pb
+
4
2 He
• Write an equation of the beta decay of the Lead-210
210
Pb
82
210
Bi
83
+
0 e
-1
Comparison of Radiation
B
o
n
e
Skin
Tissue
Organs
Your Turn: Radiation Comparison
• Write a few sentences describing the
penetrating ability and harmfulness of the
three types of radiation
Half-Life
16
1st half-life
5 seconds
8
5 seconds
2nd half-life
4
Red Balls have a
5 second half-life
3rd half-life
5 seconds
2
Half-Life
• Add applications of half-life
• Carbon-14 dating
• Radioactive Waste
• Assumptions & Limitations
• Calibration and validation
• Interpolating vs extrapolating
• Other radiodating – age of the earth &
universe
Selected Answers to Page 11 & 12
1) nucleus
2) Strong nuclear
3) stable
4) Radioactive (unstable)
5) Mass
6) Nuclear (radioactive)
7) It can only be used to date organic things
9) Protons repel each other, so they would fly apart
14) 21084Po -> 20682Pb +42He
11) 42He
3 H -> 3 He +0 e
0
15)
1
2
-1
12) -1e
230 Th -> 226 Ra +
16)
90
88
13) 42He
4 He
2
14)
17) B
18) B
Answers to Page 13 & 14
1) 0.0313 kg
3) 2.5 hr
5) 460 g
6) 7.81 g
8*) .0625 mol
(don’t panic if
you didn’t get this one)
2) 23,000 years
4) 90 years
7) 26 ug
9) 9 x 10-7 g
10) 160 sec.
238
1)
Np
93
238
Pu
94
238
2)
92 U
234
Th
90
+
+
To
Electrons
0
-1 e
4
2 He
Nuclear Fission
• Fission is when a large, unstable nucleus breaks
apart into 2 similar-sized nuclei
235
1
+ n
U
0
92
94
139
+
+
Kr
Ba
36
56
• Gives off a HUGE amount of energy!
1
3 0n
Uses for Nuclear Fission
• Atomic Bombs are an uncontrolled fission reaction
• Nuclear Power plants use a controlled fission reaction
• Energy produced by nuclear reactions is HUGE!
• 1 Uranium pellet (2 oz) produces as much energy as:
• 17,000 cubic feet of natural gas
• 1,780 pounds of coal
• 149 gallons of oil
• A nuclear bomb can release about 1-20 million times more
energy than the same mass of TNT
Advantages of Nuclear Fission
• The Good News!
• Very efficient … a little bit of fuel makes a
lot of energy
• Nuclear Power Plants do not pollute! (No
NOx, SOx, or CO2)
• Reactors do not have enough uranium for an
uncontrolled chain reaction. (subcritical mass)
• They will never explode like a nuclear bomb
Disadvantages of Nuclear Fission
• The Bad News
• Stuff left after fission reaction is unstable (“Dirty”)
• Nuclear bombs affect area for miles around blast with
radiation which takes decades to diminish
• Radioactive Waste –
• What do we do with it?
• Dangerous for 1000’s of years
• An accident could release radioactive
material
• Chernobyll
• Reactor is housed in a containment unit to prevent this
Why did Doc Oc want the tritium?
Why did Doc Oc want the tritium?
What is nuclear fusion?
• Fusion is when 2 small nuclei combine to
make a single, larger nucleus
What is nuclear fusion?
• Fusion reactions occur on stars (the sun)
• This is source of energy given off by stars
• Fusion rxns make new elements
• H + H  He
Why the big deal over nuclear fusion?
• Like fission, it produces lots of energy. (Even
more per mass of fuel used)
• Fusion would be MUCH SAFER than fission
• Products are “clean” – not radioactive
• Accidents are much less likely and less
dangerous (it can’t meltdown)
Are we close to using nuclear fusion?
• Hydrogen Bombs use nuclear fusion (not dirty)
• In over 50 years of trying, still no controllable
production of energy by fusion
• Since
positively
charged
Wouldlike
youcharges
predictrepel,
it to be
easy or hard
to fuse
nuclei repel
each
other
two
nuclei
together? Why?
• Extremely high speeds are needed to overcome
repulsion – Temperature must be 40,000,000 K
Are we close to using nuclear fusion?
• High temps would obliterate anything used to try
to contain the reaction (metal, concrete walls)
• Can use high-powered lasers to try to get up to
extremely high temperatures
• Tokamak – device that uses a magnetic field as
the “wall” to try to contain the reaction
Joint European Torus (JET) Tokamak in Oxfordshire, UK
Are we close to using nuclear fusion?
• Reactors do exist, but currently use more energy
than they produce.
• Hopefully by 2010 we will “break even”
• Possible major source of power in world by
2050
Revision: Law of Conservation
of Matter and Energy
• During both fission and fusion, Mass IS
LOST
• The mass that is lost is transferred into
HUGE amounts of energy (E=MC2)
• One little pellet of Uranium can produce as
much energy as 2000 pounds of coal
• This is why nuclear reactions give off such
a HUGE amount of energy – lost mass
changes into energy!
Time to
Check HW
Things Associated with Nuclear Chemistry
Mass Number
Nuclear Fission
Beta Decay
Ion
Atomic Mass
Plum Pudding Model
98
Things Associated with Nuclear Chemistry
Alpha Particle
Half-Life
Isotope
Atomic Number
Ground State
1.5 to 1 Ratio
99
Understanding the Motion of Electrons
• Do electrons just randomly move about the nucleus?
• If so, they could possess any given energy at any given
point in time
Story of Trumpet & Guitar
Max Planck & The PhotoElectric Effect
• When some metals are exposed to certain
wavelengths of light, the electrons absorb
the energy and are emitted. Other
wavelengths of light show no effect
Page 18B
Story of Trumpet & Guitar
Max Planck & The PhotoElectric Effect
 This seemed to indicate that electrons in the
atoms possessed specific energies and not
just any random amount of energy.
Bohr Model of Atom
(The Solar System Model)
1
2
3
• Electrons “orbit” the nucleus in
fixed, quantized energy levels
• Electrons exist only on these
energy levels
• Electrons can “jump” up energy
levels if a matching photon of
energy is absorbed (excited
state)
Bohr Model of Atom
(The Solar System Model)
1
2
3
• Electrons can “jump” up energy
levels if a matching photon of
energy is absorbed (excited
state)
• Electrons give off energy when
they “jump” back down to the
more stable ground state.
• Ground State – when the
electrons in an atom are
arranged in the lowest possible
energy level.
• Further Evidence for Bohr Model
• When heated, each element emits energy in
certain wavelengths (neon lights) -- demo
• These energies given off can be separated by a
spectroscope producing a line spectra
Lithium
• Each line a specific amount of energy with a
specific wavelength
• Each line represents a specific jump that an
electron is making within that atom
• Each element has energy levels in different places,
so they have different ‘jumps’
• Each element produces its own unique spectrum
Sodium
Mercury
Lithium
Hydrogen
Atomic Line Spectra
• Spectrum are often called the “fingerprint” of an
element
• Use spectra to determine what gases are in stars
• Demo – flame test
Jumping of Electrons
Show possible jumps for Elliot
This chart shows all the possible jumps an electron of
hydrogen can make
Each jump produces a specific amount of energy
with a specific wavelength
Each arrow represents a jump an electron can make
Energy
Level #3
Energy
Level #2
This arrow represents
an electron jumping
from level 3 to 2
Each arrow represents a jump an electron can make
Energy
Level #3
Energy
Level #2
This jump is labeled
“a” in the
“Balmer Series”
Each jump produces a specific amount of energy
with a specific wavelength
500
400
e d c
b
600
700
a
Hydrogen Balmer Series
An electron jumping from level 3 to 2
will always give off energy with a
wavelength of 650 nm (red light)
“a” in the
“Balmer Series”
Warm-Up:
Turn to page 28 in your packet and determine
the wavelength of the energy produced when
a hydrogen electron jumps from energy level
# 6 to 3
B) If 1 Angstrom = 1 x 10-9 m, what is this
wavelength in meters?
What
jump
makes this
blue?
500
400
e d c
b
600
a
Hydrogen Balmer Series
700
Page 28 – jumps of hydrogen
• HW – Page 29
Quantum Mechanical Model
Our Modern View of the Atom
Bohr Model vs Quantum Model
The electrons do not travel in fixed paths as
Bohr suggested, however their motion is not
entirely random either.
The electrons have regions where have high
probabilities of being found
Space Orbital - area where an electron will be
within 90% of the time.
Quantum Numbers
The 4 Quantum Numbers are like an “address”
describing the location of an electron
No two electrons have the exact same set of
quantum numbers
Principal Quantum Number (n)
Describes the energy level that electron is in
Energy level represents average distance an
electron is from nucleus
The larger the energy level, the larger the orbital
and farther away from nucleus electron is
12
3
Angular Quantum Number (l)
Sometimes called
“Orbital” or “Azimuthal”
Q.N.
Describes which type of
orbital electron is in.
Orbitals are defined by
their shape.
Book page 142…..
S orbitals (l=0)
Shaped like a sphere or
ball
Only 1 present in each
energy level
P orbitals (l=1)
Shaped like an hourglass,
dumbbell, peanut
“P’s come in 3’s” -- have
three on an energy level
D orbitals (l=2)
Four leaf clover shaped,
Daisy, “Double-peanut”
How many?
5 on an energy level.
F orbitals (l=3)
Too complex and variable to visualize shape
How many?
7
Magnetic Quantum Number(ml)
Tells which “p” orbital electron is in.
Named according to axis they are oriented
along.
Py
Px
Pz
Spin Quantum Number(ms)
Each orbital can hold up to 2 electrons
2 Electrons may occupy the same orbital only if
they are spinning in opposite directions.
+1/2 (or 1) - first electron in orbital
-1/2 (or -1) - second electron in orbital
“+” and “-” indicate direction, NOT CHARGE
Learning Check
Give the quantum numbers for the second
electron placed in a dumbbell-shaped orbital in
the horizontal position in the 4th energy level.
Orbitals & Energy Levels
Not every energy level
has every orbital:
Energy
Level
Orbitals
Present
Max eCapacity
1
s
2
2
s,p
8
3
s,p,d
18
4
s,p,d,f
32
HomeWork – due tomorrow
Complete Page 21 & 22
Complete Pages 14B & 14C
Orbital “Order of Filling”
Shortcut Electron Config
Looking at the Pd Table
s1
(special no rule-breaker version)
p1 p2.........
s2
s-Block
d1
d2 d3
d4* d5
d6 d7 d8 d9* d10
p-Block
d-Block
p6
Looking at the Pd Table
s1
p1 p2.........
s2
s-Block
d1
d2 d3
d5 d5
d6 d7 d8 d10 d10
p-Block
d-Block
p6
Your Turn: Shorthand Config
• Do Shorthand Electron Configuration for:
• Sr
• Mo
• Sb
3. Electron Dot Notation
•
•
•
•
Electron dot notation shows only outer shell (valence) e’s
Valence electrons are the outermost electrons in an atom
– or - the electrons in the highest energy level
Example: Oxygen 1s22s22p4
6 valence electrons
Outer Shell
What’s the
highest energy
level that
has
e’s
How
many
valence e’s
3. Electron Dot Notation
Inner Shell
4 valence electrons
• Example: Ge 1s22s22p63s23p64s23d104p2
Outer Shell
Can d orbital
electrons ever be in
the outer shell?
What’s the
highest energy
How many
level that has
e’s e’s
valence
Electron Dot Notation
•
Only s and p electrons can ever be in outer shell
8 electrons to fill the outer shell
• It takes __
• A filled outer shell is called an octet
• An octet is the most stable configuration an atom
can have
What elements
• Noble Gases have octets
have octets?
1 2
# of valence e’s
3 4 5 6 7 8
How many valence
e’s does sulfur have?
Electron Dot Notation
S
How many valence
electrons?
S
3s
3p
Electron Dot Notation
Unpaired
electron
S
Electron Pair
Electron Dot Notation
5
7
4
8
X
6
3
1
2
Your Turn: Electron Dot
• Do the electron dot notation for the
elements listed on the top part of page
• Also – tell how many pairs and unpaired
electrons each element has
The following slides are generally not
covered in CP Chem
Don’t worry about the following unless instructed
to.
Order of Filling “Rule Breakers”
 The Reasons:
 Having a filled energy level is a very
stable configuration (Noble Gases)
Ne
2s
2p
 Having a filled subshell is also extra
stable
Mg
3s
3p
 Having a half-filled subshell is also a
bit extra stable
P
3s
3p
Order of Filling “Rule Breakers”
Who breaks the rules?
Elements whose last d and f orbitals are 1
electron short of being filled or half filled
4s
4s
3d
Almost
Filled
3d
Almost
Half- Filled
Order of Filling “Rule Breakers”
 What do they do?
An electron is moved from the higher ‘s’ orbital and
placed in the d orbital to fill or half-fill it
4s
4s
3d
3d
Filler
Half-Filler
s and p orbitals do not do this. The energy
difference between them is too great. (see poster)
Order of Filling “Rule Breakers”
Bottom Line:
You will never have a final answer with d
orbitals looking like this:
Or this:
5s24d9
5s14d10
5s24d4
5s14d5
Order of Filling Rule Breakers
Go to Your Homework
Identify any rule-breaker
Write the correct configurations in