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Chemistry Chapter 5 Notes
Section 5.1: Light and
Quantized Energy
1) Rutherford’s model is great
for showing where the protons
and neutrons in an atom are,
but it did not given any
information about where to find
the electrons or why the
negative electrons did not just
get stuck to the positive
nucleus.
2) When elements were heated
in a flame, the light they gave
off was not a continuous
spectrum (like with white light)
but instead it was a series of
lines.
Each element gave off a
different set of lines (called the
atomic emission spectrum),
and it was found to be because
of the electrons in each
element.
This meant light could give
scientists a clue of how
electrons are arranged.
Unfortunately, scientists are not
certain about what light is like,
sometimes it is like a wave,
and sometimes it is like a
particle.
A) When light is like a wave it is
called electromagnetic
radiation, and is part of the
electromagnetic spectrum (also
includes radio waves, TV
waves, microwaves, UV waves,
X-rays, and gamma-rays).
As a wave, there are many
measurements that can be
made:
As a wave, there are many
measurements that can be
made:
i) The tops of a wave are called
crests.
As a wave, there are many
measurements that can be
made:
i) The tops of a wave are called
crests.
ii) The bottoms of a wave are
called troughs.
iii) The distance from the rest
position (no wave) to a crest or
trough is called the amplitude.
iv) The length of one wave is
called a wavelength and has a
symbol of “λ” (lambda).
Wavelength is measured in
meters. Usually wavelengths
are very small for
electromagnetic waves
v) The number of waves that
pass a point in one second is
called the frequency and has a
symbol of “ν” (nu). Frequency
is measured in Hertz (1/s)
How many hertz is the first wave?
How many hertz is the second wave?
vi) All electromagnetic radiation
travels at the same speed as
light, symbolized as “c”, and is
3 x 108 in the vacuum of space
vii) Speed, wavelength, and
frequency are all
mathematically related
as:
c = λ ν;
this means frequency and
wavelength are inversely
related
Label the crest, trough,
amplitude, and wavelength of
this wave:
Label the crest, trough,
amplitude, and wavelength of
this wave:
Crest
Wavelength
Amplitude
Trough
What is the frequency of red
light which has a wavelength of
700nm ( .0000007 m)?
What is the frequency of red
light which has a wavelength of
700nm ( .0000007 m)?
If c = λ ν, then v = c
λ
What is the frequency of red
light which has a wavelength of
700nm ( .0000007 m)?
v = c = 300000000 m/s
λ
.0000007 m
What is the frequency of red
light which has a wavelength of
700nm ( .0000007 m)?
v = c = 300000000 m/s
λ
.0000007 m
V = 4.29 x
14
10
1/s or Hz
What is the wavelength of
violet light which has a
14
frequency of 7.5 x 10 Hz ?
What is the wavelength of
violet light which has a
14
frequency of 7.5 x 10 Hz ?
If c = λ ν, then λ = c
v
What is the wavelength of
violet light which has a
14
frequency of 7.5 x 10 Hz ?
λ=c
v
= 300000000 m/s
7.5 x
14
10
1/s
What is the wavelength of
violet light which has a
14
frequency of 7.5 x 10 Hz ?
λ=c
v
= 300000000 m/s
7.5 x
14
10
1/s
λ = .0000004 m or 400 nm
B) When light is like a particle it
is called a photon. Light is like
a particle because there are
only certain amounts of energy
it can have, the minimum
amount is called a quantum.
i) Max Planck found this energy
could be calculated with the
formula:
E = h ν;
where E = energy, measured in J
h = Planck’s Constant = 6.626 x 10-34 Js
ν = frequency, measured in Hz or 1/s
What is the energy of violet
light ?
What is the energy of violet
light ?
E=hv
What is the energy of violet
light ?
E=hv
h = 6.626 x
-34
10
Js
v = 7.5 x 1014 1/s (from earlier)
What is the energy of violet
light ?
E = (6.626 x 10-34 Js)(7.5 x 1014 1/s)
What is the energy of violet
light ?
E = (6.626 x 10-34 Js)(7.5 x 1014 1/s)
E = 4.97 x
-19
10
J
ii) Once the minimum amount
of energy is calculated, the
actual energy can be a multiple
of the quantum amount. (1 x E,
or 2 x E, or 3 x E, etc)
Section 5.2 Quantum Theory
and the Atom
1) Because of the wave-particle
duality of light, electrons are
considered to be a particle that
can behave like a wave.
Mainly, it is seen that there are
only certain energy levels
where an electron can be found
Much like going up a ladder,
the electron cannot go up or
down a partial energy level,
and the more energy it has the
higher the energy level it can
be in.
•
A) Niels Bohr used this to
explain why hydrogen (only has
1 electron) would give several
lines in the emission spectrum.
He said the electron could be in
different rings around the
nucleus just like the planets are
in different orbits around the
sun. This is sometimes called
the planetary model of the
atom
B) Louis de Broglie (18921987), Werner Heisenburg
(1901-1976), and Erwin
Schrődinger (1887-1961)
separately did experiments and
calculations that showed Bohr’s
model was not correct for any
element other than hydrogen.
Bohr’s model was replaced by
the quantum mechanical
model of the atom.
This new model used
principal quantum
levels that were similar
to Bohr’s orbits, but
then divided the
principal quantum level
into sublevels.
i) The principal quantum level is
a number from 1-7, with 1
being the lowest energy and 7
being the highest in energy.
This number often represents
the period on the periodic table
in which we find the element
ii) The sublevels are s, p, d,
and f, with s being the first
sublevel and f the last
(1) The s sublevel only has 1
orbital, and the orbital holds 2
electrons
(2) The p sublevel has 3
orbitals, and each orbital holds
2 electrons, for a total of 6
(3) The d sublevel has 5
orbitals, and each orbital holds
2 electrons, for a total of 10
(4) The f sublevel has 7
orbitals, and each orbital holds
2 electrons, for a total of 14
iii) We put together the principal
quantum number and sublevel
letter to talk about a specific
orbital, but not all sublevels are
possible for each energy level.
principal Quantum Level
1
2
3
4–7
1s
2s 2p
3s 3p 3d
4s 4p 4d 4f
Possible Sublevels
s
s, p
s, p, d
s, p, d, f
5s 5p 5d 5f
6s 6p 6d
7s 7p
Section 5.3: Electron
Configurations
1) Now that scientists know
more specifically where the
electrons are, we need to be
able to show this in a simple
manner so we can
communicate easily with
other scientists
This arrangement of electrons
in an atom is called an electron
configuration.
2) There are three rules that
we must follow when making
an electron configuration:
a) The aufbau principle says
electrons must fill lower
energy levels before
electrons can fill higher
energy levels. This means 1s
is filled before 2s, etc
B) The Pauli exclusion principle
says that only two electrons
can fill each orbital (remember
s has 1 orbital, p has 3, d has
5, and f has 7).
So s holds 2 electrons, p holds 6
electrons, d holds 10 electrons,
and f hold 14 electrons.
C) Hund’s rule says electrons
must spread out between the
orbitals (p, d, or f) before they
double up.
Yes
No
□□□
□□□
2p
2p
3) If we use boxes to represent
orbitals, then the following
aufbau diagram shows all the
possible places an electron
could be:
Notice that the energy
increases from bottom to top,
High
Energy
Low
Energy
and some of the orbitals do not
fill in the same number order as
the others.
If you fill from the bottom to the
top, spreading out the electrons
before doubling them up, then
you should be just fine.
Hydrogen
H
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Helium
He
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Completely
Filled
Lithium
Li
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Beryllium
Be
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Boron
B
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Carbon
C
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Nitrogen
N
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Oxygen
O
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Fluorine
F
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Neon
Ne
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Completely
Filled
Sodium
Na
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Magnesium
Mg
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Aluminum
Al
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Silicon
Si
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Phosphorus
P
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Sulfur
S
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Chlorine
Cl
□ □ □ 3p
□ 3s
□ □ □ 2p
□ 2s
□ 1s
Argon
Ar
□ □ □ 3p
□ 3s
□
□ 2s
□ 1s
Completely
Filled
□ □ 2p
4) The actual order of filling is:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d
5p 6s 4f 5d 6p 7s 5f 6d 7p
At this time show the orbital viewer at
http://intro.chem.okstate.edu/WorkshopFolder/
Electronconfnew.html
Have out color-coded periodic
tables before starting.
4) The actual order of filling is:
1s 2s 2p 3s 3p 4s 3d 4p 5s 4d
5p 6s 4f 5d 6p 7s 5f 6d 7p
5) In order to save paper, often
this is condensed to just a
horizontal row called an orbital
diagram:
6) Arrows are
used to
represent the
electrons, so if
two arrows go in
the same box,
one points up
and the other
points down.
Nitrogen
N
□ □ □ 2p
□ 2s
□ 1s
Becomes:
□
□
□□□
1s
2s
2p
Cobalt (27 electrons – 27 arrows)
□ □ □□□ □ □□□ □ □□□□□
1s 2s
2p 3s
3p 4s
3d
Cobalt (27 electrons – 27 arrows)
□ □ □□□ □ □□□ □ □□□□□
1s 2s
2p 3s
3p 4s
3d
Bromine (35 electrons)
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s
3p 4s
3d
4p
Oxygen (how many arrows?)
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s 3p
4s
3d
4p
Oxygen
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s 3p
4s
3d
4p
Calcium (how many arrows?)
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s 3p
4s
3d
4p
Calcium
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s 3p
4s
3d
4p
Gallium (how many arrows?)
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s 3p
4s
3d
4p
Gallium
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s 3p
4s
3d
4p
7) Even horizontal boxes can
be too much to write, so the
number of electrons in each
sublevel is turned into a
superscript and is written out
with the quantum number and
the sublevel letter.
This is called an electron
configuration.
A) If all the orbitals are filled,
the entire sequence would be:
2
2
6
2
6
2
10
6
1s 2s 2p 3s 3p 4s 3d 4p
5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2
14
10
6
5f 6d 7p
Nitrogen
N
□
□
□□□
1s
2s
2p
Becomes:
1s2 2s2 2p3
Cobalt
□ □ □□□ □ □□□ □ □□□□□
1s 2s
2p 3s
3p 4s
Becomes:
1s2 2s2 2p6 3s2 3p6 4s2 3d7
3d
Bromine (35 electrons)
□ □ □□□ □ □□□ □ □□□□□ □□□
1s 2s
2p 3s
3p 4s
3d
Becomes:
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
4p
What is the electron
configuration for:
Oxygen?
What is the electron
configuration for:
Oxygen:
2
2
4
1s 2s 2p
What is the electron
configuration for:
Oxygen:
2
2
4
1s 2s 2p
Calcium?
What is the electron
configuration for:
Oxygen:
2
2
4
1s 2s 2p
Calcium:
2
2
6
2
6
2
1s 2s 2p 3s 3p 4s
What is the electron
configuration for:
Oxygen:
2
2
4
1s 2s 2p
Calcium:
2
2
6
2
6
2
1s 2s 2p 3s 3p 4s
Gallium?
What is the electron
configuration for:
Oxygen:
2
2
4
1s 2s 2p
Calcium:
2
2
6
2
6
2
1s 2s 2p 2s 3p 4s
Gallium:
2
2
6
2
6
2
10
1
1s 2s 2p 3s 3p 4s 3d 4p
8) If writing out the entire
electron configuration is too
much, we can use the previous
(in the periodic table) noble gas
to take the place of part of the
electron configuration:
Example:
2
2
6
2
1s 2s 2p 3s
Magnesium:
Neon: 1s22s22p6
Noble Gas configuration:
Magnesium: [Ne] 3s2
Example:
Polonium:
1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p4
Xenon:
1s22s22p63s23p64s23d104p65s24d105p6
Polonium:[Xe]
2
14
10
4
6s 4f 5d 6p
9) When the electron
configuration is written for an
element using the noble gas
configuration the electrons
written after the noble gas are
the ones that appear on the
outside of the atom.
These electrons are called
valence electrons.
When elements bond to form
compounds, it is these
electrons that are involved.
The amount of valence
electrons makes a big
difference in how the element
will bond, so to make it easy to
predict, we draw electron dot
diagrams.
A) In an electron dot diagram,
we use the symbol of the
element and dots to represent
the number of valence
electrons.
B) Only s and p electrons with
the highest quantum number
count for dot diagrams, even if
there are d and f electrons after
the noble gas.
Lithium = [He]
So
1
2s
Li
Beryllium = [He]
So
Be
2
2s
Boron = [He]
2
1
2s 2p
So
B
Carbon = [He]
So
2
2
2s 2p
C
Nitrogen = [He]
So
N
2
3
2s 2p
Oxygen = [He]
So
2
4
2s 2p
O
Fluorine = [He]
So
F
2
5
2s 2p
Neon = [He]
So
2
6
2s 2p or
Ne
[Ne]