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Electron Configuration
EQ: How are electrons arranged
around an atom?
HEISENBURG UNCERTAINTY
PRINCIPLE:
• Impossible to know precisely both velocity
& position of a particle at the same time.
• In order to find position of an electron,
need photon of light.
• Photon “bumps” into electron,
changing its position.
Quantum – Mechanical Model of
the Atom
• Our current model.
• Atomic Orbital:
– Describes the electron’s
probable location
– 3-D region around the
nucleus; a blurry cloud of
negative charge
(discuss with your neighbor)
Compare and contrast the plum
pudding model and the quantum
mechanical model.
Electron Configuration
• This is the arrangement of electrons in
an atom.
• Electrons are arranged so that the atom
has the lowest possible energy
• The most stable electron arrangement
is called the element’s ground-state
electron configuration
Arrangement of Electrons in Atoms
Electrons in atoms are arranged as:
LEVELS (n)
SUBLEVELS (l)
•Each energy level has a number called
the Principal Quantum Number, n
•Currently n can be 1 thru 7, because
there are 7 periods on the periodic table
Learning Check
1. Who wrote the uncertainty principle?
2. What was uncertain about it?
3. Create a simile, metaphor, or other
figure of speech to help you remember
this principle.
4. How many energy levels are there and
what do the correspond to?
Sublevels
• The most probable area to find
electrons takes on a particular shape.
• So far, we have 4 shapes. They are
named s, p, d, and f.
• No more than 2 e- assigned to an
orbital – one spins clockwise, one spins
counterclockwise.
4 Orbitals (s, p, d and f)
f-orbitals
The Four Orbitals
• All s orbitals are spherical
shaped (1 per level)
• All p orbitals are dumbbell
shaped and along three
axis’s
(x, y, z) (3 per level)
• All d (5 per level) and f
(7 per level) orbitals are
complex shapes
Orbitals and Electron Capacity of the First Four Principle
Energy Levels
Number of Maximum
Principle
Number of
Type of
orbitals
number of
energy
orbitals
sublevel
per
electrons
level (n)
per type
level(n2)
(2n2)
1
s
1
1
s
2
4
8
p
3
1
3
p
9
d
5
s
1
3
4
32
d
f
7
Orbitals and Electron Capacity of the First Four Principle
Energy Levels
Number of Maximum
Principle
Number of
Type of
orbitals
number of
energy
orbitals
sublevel
per
electrons
level (n)
per type
level(n2)
(2n2)
1
s
1
1
2
s
1
2
4
8
p
3
s
1
3
p
3
9
18
d
5
s
1
p
3
4
16
32
d
5
f
7
Aufbau principle
• Each electron
occupies the lowest
energy orbital
available
• They are filled in
order s, p, d, and f
(there is some
overlap between d
and f)
Learning Check
1. Which orbital is the simplest?
Why?
2. (think and pair share) Which
orbital do you like the best? Why?
Pauli exclusion principle
• a maximum of two electrons may occupy a
single atomic orbital, but only if the
electrons have opposite spins
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.
• Ex.  
p

then  
p
_
Quiz
• According to Aufbau, electrons fill the orbital
having the _________ energy.
• Pauli’s Exclusion Principle states that if 2
electrons are in the same orbital they must have
__________ spins.
• Hund’s Rule states that when filling p, ____, and f
orbitals, you must first fill in a single electron,
same _________ in each orbital before pairing up.
See Other Powerpoint
Writing Configurations
• Start by finding the number of electrons in
the atom
• Identify the sublevel that the last electron
added is in by looking at the location in
periodic table
• Draw out lines for each orbital beginning
with 1s and ending with the sublevel
identified
• Add arrows individually to the orbitals until
all electrons have been drawn
Electron Configurations
4
Number of
electrons in
the sublevel
Energy Level
Sublevel
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6
6s2 4f14…
What is the ending configuration for
the following elements?
•
•
•
•
•
•
•
•
•
•
H
He
Li
Na
Mg
Al
Ar
K
Sc (“d” is 1 step behind)
U (“f” is 2 steps behind)
ELECTRON NOTATION
• Summarize electron configuration.
• 1s2 2s2 2p4
NOBLE GAS NOTATION:
• 1) Write previous noble gas in brackets.
• 2) Then write each block that is left over.
• Ex. for P, # 15. What is the previous
noble gas?
• 1) Write previous noble gas: Ne
• This represents Neon’s 10 electrons.
• 2) Write what is left over:
•
Ne 3s23p3.
VALENCE ELECTRONS
• Electrons in the atom’s
outermost energy level
• Include: s & p orbitals only
or
• Look at the Group Number
• Which group has a full set of
valence electrons? The Noble
gases. This is what makes the
noble gases stable.
Electron Dot/Lewis Dot Diagrams
• A visual representation used by scientists to help
show chemical bonds
• Only involves valence electrons
• Consists of the elements symbol, which represents
the innermost electrons too, and the valence
electrons surrounding it.
• Example: Lithium has 3 electrons but only 1
valence----Li
• The number of valence electrons determines how
many and what this atom (or ion) can bond to in
order to make a molecule
Valence Electrons
• In order to be stable, atoms must empty or fill
their outermost level.
• Since the outer level contains two s electrons and
six p electrons (d & f are always in lower levels),
the optimum number of electrons is eight.
• This is called the octet rule.
EQ #3
What is the
orbital
configuration
of a neutral
atom?
EQ #11
How can an
element be
identified by
light emission
and the
movement of
electrons?
WAVE NATURE OF LIGHT:
Important in understanding electrons.
• Electromagnetic radiation – This is the form of
energy which includes visible light, microwaves,
X-rays, radio waves, etc.
Long wavelength --> small frequency
Short wavelength --> high frequency
ELECTROMAGNETIC RADIATION
TRAVELS IN WAVES
• Wavelength () – distance between 2 waves
• Units: m, cm, nm (1nm = 1 x 10-9 m)
• Frequency () - # waves that pass a given point per
second
• Units: waves/sec, hertz (1 wav/s = 1 hz)
• Amplitude - wave’s height
from origin (middle) to crest.
PARTICLE NATURE OF LIGHT: Explains
why heated objects emit specific frequencies of light.
• Iron – dark gray at room
temperature, red when
hotter, bluish when very
hot.
• It is emitting a photon of
light that carries the
electromagnetic radiation.
VELOCITY: All electromagnetic radiation
travels at the speed of light, “c”.
• c = 3.00 x 108 m/s
• c = 
• Wavelength & frequency:
inversely proportional
• If wavelength increases,
frequency decreases.
WHITE LIGHT: Prism separates
into a continuous spectrum -- ROYGBIV
Red Light – Lower Frequency (longer wavelength) than
violet light.
Quiz
• 1) Name 3 types electromagnetic radiation.
• 2) What is the velocity of all
electromagnetic radiation?
• 3) The distance between waves is ____().
• 4) The number waves per second is ___().
• 5) The higher the frequency, the ___the
wavelength.
• 6) A prism separates white light into the ___
spectrum.
MAX PLANCK (1900)
Quantum concept of energy:
• Matter gains or loses
energy in small
specific amounts
called quanta.
• Quantum –
minimum amount of
energy that can be
gained/lost by an
atom.
ATOMIC EMISSION SPECTRA:
Set of frequencies of electromagnetic waves emitted
by atoms of an element
• Spectrum is unique for each element.
• Ex. Strontium atoms – Emit a characteristic red color.
• Can use spectrum to identify an element.
• Atomic spectrum consists of several individual lines of
color
• (Not continuous).
Flame Tests
•Elements emit a characteristic color.
•When the element is heated and gains
energy, the electron moves to higher energy
level.
•When electron returns to the ground state, a
photon of light is emitted corresponding to
the difference in energy
An excited lithium atom emitting a
photon of red light to drop
electrons to a lower energy state.
An excited H atom returns to a
lower energy level.
Quiz
• The set of frequencies emitted by atoms of an
element is called the atomic ____ _____.
• In the flame tests, what causes the characteristic
color of the element?
EQ #11
How can an
element be
identified by
light emission
and the
movement of
electrons?
EQ #4
How does an
atom’s
electron
configuration
affect its
chemical
properties?
Valence Electron Review
• Electrons in the atom’s
outermost energy level
• Include: s & p orbitals only
or
• Look at the Group Number
• Which group has a full set of
valence electrons?
• The Noble gases. This is what
makes the noble gases stable.
Valence Electrons Review
• In order to be stable, atoms
must empty or fill their
outermost level.
• Since the outer level contains
two s electrons and six p
electrons (d & f are always in
lower levels), the optimum
number of electrons is eight.
• This is called the octet rule.
Write Orbital Notation for each of the
following and determine the number
of valence electrons. Will each of
these gain or lose electrons for a stable
octet?
•
•
•
•
Lithium
Magnesium
Chlorine
Sulfur
Bohr’s Model
Increasing energy
Fifth
Fourth
Third
Second
First
Nucleus
 Further away
from the nucleus
means more
energy.
 There is no “in
between” energy
 Energy Levels
Bohr’s Model
Nucleus
Electron
Orbit
Energy Levels
Bohr Model
• We use the Bohr Model because of the
simplicity of drawing the valence electrons
and the sharing or loss/gain of these valence
electrons.
• Nucleus is far too large relative to the
distance of the electrons.
• Remember that electrons do not orbit the
nucleus, but drawing and using a model of
the quantum mechanical atom is complex.
Valence Electrons and Chemical
Properties
• The number of valence electrons determines
the atom’s ability to gain, lose, or share
electrons to combine and form compounds.
• Atoms gain or share valence electrons in
order to achieve a stable noble gas
configuration with a full energy level.
EQ #4
How does an
atom’s
electron
configuration
affect its
chemical
properties?
EQ #12
Compare
and
contrast the
types of
chemical
bonds.
Periodic Table
• Metals – Cations (+)
• Nonmetals – Anions (-)
• Metalloids
Cations
• Metals
• Positive Ion
• Metal atoms loses 1 or more
valence electrons to have a
stable octet.
Anions
• Nonmetals
• Negative Ion
• Nonmetal
atoms gain
electrons to
have a stable
octet (8) in
valence shell.
Periodic
Table
• Main Group Elements
• Transition Metals
• Inner Transition Metals
Chemical Bond
• The force of attraction
between two elements.
• Three Types of Bonds:
1. Ionic
2. Covalent
Polar and Nonpolar
3. Metallic
1. Ionic Bonds
Transfer of
electrons
(from metal
to nonmetal).
1. Ionic Bonds continued
• The bone represents an electron.
• The dog that takes the bone is negative.
• The dog that loses the bone is positive.
1. Ionic Bonds continued
• Electrons are transferred
from a metal to a
nonmetal.
– Cations give up electrons;
anions take electrons
– Both atoms achieve an
octet in their outermost
orbital
– The attractive forces bring
the cation and anion
together
Ionic Bonds Quiz
• 1) In an ionic bond, electrons are _____.
• 2) The type of electrons involved are ___ or outer shell
electrons.
• 3) Metals ___ electrons, nonmetals ___ electrons in
order to get a ___ gas configuration (stable octet).
• 4) Cations have a __ charge and are formed by __.
• 5) Anions have a __ charge and are formed by __.
• 6) ____ charges hold the compound together.
2. Covalent Bonds
• Valence Electrons are shared by both atoms
– Between nonmetals and nonmetals
– Electron pairs form a bond
– Both atoms achieve an octet in their outermost
orbital
2. Covalent Bonds Continued
2 Types of Covalent bonds
• 1. Polar Covalent:
Electrons are
shared unequally.
2. Nonpolar Covalent
Electrons are
shared equally.
Polar Covalent Molecules
• Unevenly matched but willing to share
• Stronger dog gets a larger portion of the bone
• Element that’s more electronegative pulls the pair of
electrons towards it
Nonpolar Covalent Molecules
• Dogs of equal strength
• Both dogs have equal attraction for the bone
3. Metallic Bonds
•
Occur when the large d and f sublevels of
transition metals overlap and allow the
electrons to travel freely between them.
3. Metallic Bonds continue
• “Mellow dogs with plenty of bones to go
around.”
• Electrons move through the substance with
little restriction
EQ #12
Compare
and
contrast the
types of
chemical
bonds.
EQ #6
Compare
and
contrast
alpha,
beta, and
gamma
radiation.
Keep in Mind:
Nuclear Reactions vs. Chemical Changes
• Nuclear reactions involve the nucleus
(protons and neutrons and electrons) (change
of element).
• Chemical Reactions involve electrons
(bonding) (no change of element).
• The opening of the nucleus releases a
tremendous amount of energy.
• Chemical reactions involve releases of
smaller amounts of energy.
What is Radiation?
• When an unstable isotope nucleus decays
(to become more stable), radiation is
released.
• This releases a tremendous amount of
energy.
• The element decays into a new element.
• There are three types of radiation
1. alpha
2. beta
3. gamma
TYPES OF RADIATION
Type
Relative Size and
Composition
Penetration
Alpha
Large
Helium Nucleus
(positive +)
Very Small
Electrons
(negative -)
Sheet of
Paper
Beta
Gamma
Not a particle,
only energy
(no size, no
charge)
Aluminum
Foil
Lead
Shielding
EQ #6
Compare
and
contrast
alpha,
beta, and
gamma
radiation.
EQ #7
Compare
and
contrast
fission and
fusion.
Fission
Fusion
Fission
• This is the
process of
breaking larger,
unstable atoms
apart into
smaller ones.
• Fission releases
tremendous
amounts of
energy.
• Nuclear power
plants
Chain Reaction
Fission – Chain Reaction
Fission in Nuclear Power Plants
Fission in Nuclear Power Plants
Fusion
• Fusion is the
process of fusing
together smaller
elements to make
larger ones.
• Fission releases
tremendous
amounts of
energy.
• Occurs in the sun
and other stars.
EQ #7
Compare
and
contrast
fission and
fusion.
EQ #8
How does
nuclear
fusion create
all elements
heavier than
helium?
Fusion
• In stars, nuclear fusion of hydrogen atoms
with other elements creates elements with
even larger atomic numbers.
EQ #8
How does
nuclear
fusion create
all elements
heavier than
helium?
EQ #10
What are the
pros and cons
to nuclear
energy as an
alternative
energy
source?
Nuclear Energy
Pros
• Nuclear energy does not cause air pollution.
Cons
• There is a limited amount of nuclear fuel.
• The spent fuel is radioactive, causing a
transportation and storage issue.
• The water used in the cooling process can cause
problems when released into the environment.
Nuclear Power Plant Locations
Nuclear Fission and Power
• Currently about 103
nuclear power plants
in the U.S. and about
435 worldwide.
• 17% of the world’s
energy comes from
nuclear energy.
EQ #10
What are the
pros and cons
to nuclear
energy as an
alternative
energy
source?
EQ #9
How is the
process of
half-life
related to
radioactive
decay?
Decay of 20.0 mg of 15O.
What remains after 3 half-lives? _____
After 5 half-lives? _____
Half-Life
• Half-life is the
average time for
one-half of a
radioisotope to
decay into more
stable isotopes.
• The amount of the
radioisotope
follows the
sequence ½, ¼, 1/8,
1/16 …0 after each
half-life.
Don’t Forget: Radiation is
released during radioactive
decay.
Half-Life Problem:
• The half-life of tritium, H-3 is 12 years.
• If you start with 200 g of tritium, then how
many half-lives have passed if you only
have 25 g remaining?
• 200 g  100 g (1 half-life)
• 100 g  50 g (2 half-lives)
• 50 g  25 g (3 half-lives)
• Ans. 3 half-lives.
Half-Life Quiz
• Half-life of Ra-222 is 3.8 seconds. How
much of a 200 g sample remains after 11.4
seconds?
• # half-lives = 11.4 sec/3.8 sec = 3
• After 0 half-life = 200 g (0 s)
•
1
= 100 g (3.8s)
•
2
= 50 g (7.6s)
•
3
= 25 g (11.4s)
Half-Life Quiz
• What is the half-life of an isotope of Tritium (H-3)
if a 400 g sample decays to 50 g in 36 years?
• Find # half lives:
•
•
•
400 g = 0 half life
200 g = 1 half life
100 g = 2 half lives
50 g = 3 half lives
• It took 36 years for 3 half-lives.
• 36 years/3 half-lives
• = 12 yrs./half-life
EQ #9
How is the
process of
half-life
related to
radioactive
decay?
Atomic
Theory
The
End