The Quantum Model of the Atom
By the end of this lesson, I will be able to:
 Differentiate between the Bohr model of the atom and the Quantum
model of the atom.
 Explain the following terms: orbital, electron cloud, suborbital,
Aufbau Principle, Hund’s Rule, Pauli Exclusion Principle, electron
configuration, orbital notation, noble gas electron configuration.
 Characterize s, p, d, and f orbitals by shape (s and p only), number of
suborbitals, and maximum number of electrons.
 Use the Aufbau Principle, Hund’s Rule, the Pauli Exclusion
Principle, and a periodic table to construct the electron
configuration, noble gas electron configuration, and orbital notation
of an element.
Compare the Quantum model of the atom to the earlier Bohr
model of the atom.
? What is the main difference between the Bohr model and the
Quantum model?
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Vocabulary!
Orbital a three-dimensional region around the nucleus
where there is a high probability of finding an electron –
these regions are collectively known as the electron
cloud .
Look at the handout titled “s and p Orbitals”.
This handout shows some of the s and p orbitals that exist around
the nucleus of the atom. It also shows the maximum number of
electrons that each orbital can hold.
? Describe the three-dimensional shape of an s orbital.
? What is the maximum number of electrons that can be found in
an s orbital?
? Describe the three-dimensional shape of a p orbital.
? What is the maximum number of electrons that can be found in a
p orbital?
 Open the envelope labeled “Atomic Orbital Cutouts” and ask your
teacher for a dry erase marker.
 Remove the s and p orbital cutouts from the envelope.
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 Fill the s orbital with electrons by coloring in the electron circles
with a dry erase marker.
 Separate the three p suborbitals and spread them out as shown
below.
 Fill the p orbital with electrons by coloring in the elecron circles
with a dry erase marker. Color in the electron circles in the p
orbitals exactly as described below –
st
2 Electron
th
5 Electron
1 Electron
4 Electron
nd
th
rd
3 Electron
th
6 Electron
? What is the maximum number of electrons that can be found in a
p suborbital?
 Reassemble the p orbital and clean off the orbital cutouts with a
paper towel.
Vocabulary!
Suborbital: probability regions within p, d, and f orbitals.
Each suborbital can contain a maximum of two electrons.
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Electrons are added to orbitals in a specific order. The lowest
energy orbitals are filled first. The illustration below shows the
order that the orbitals should be filled.
1s → 2s →
Vocabulary!
?
2p
3s
→
→
3p
→
4s
Aufbau Principle: Electrons fill the lowest energy
orbitals first.
For each of the following atoms, correctly fill the orbitals from
lowest to highest energy level by filling in the electron circles
on the orbitals. (The relative sizes of the orbitals are not
indicated.)
6
Carbon
electron
: Carbon (C)
C
12.01
# Electrons: __6__
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Oxygen – O
# Electrons: _____
Phosphorus – P
# Electrons: _____
Potassium – K
# Electrons: _____
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Look at the filled orbitals for the atom sodium.
The
for the atom sodium is shown beneath the
a picture showing sodium’s filled orbitals.
Compare the picture of sodium’s orbitals with its electron
configuration.
? What do you think the superscript numbers in the electron
configuration represent?
Vocabulary!
Electron Configuration: a notation that shows the
distribution of electrons in the quantum model of the
atom. The electrons are indicated by a superscript.
? Use the illustrations below to write the electron configurations
for the following atoms.
Electron Configuration: ___________________________
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Electron Configuration: __________________________
Electron Configuration: __________________________
Electron Configuration: __________________________
Notice that the sum of the superscripts in an electron
configuration is equal to the atomic number and can be
used to identify an element from the electron configuration.
The sum of the superscripts in the following electron
configuration is 5. The electron configuration represents
the atom boron whose atomic number is 5
1s 2s 2p
5
Boron
B
10.81
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? Identify the following elements from their electron
configurations.
1s22s22p63s2 ___________________
1s22s22p2 ___________________
1s22s22p63s23p4 ___________________
1s22s22p63s23p64s2 ___________________
Look at the electron configuration for the atom oxygen.
The
for the atom oxygen is drawn beneath its
electron configuration.
Compare the electron configuration for the oxygen atom with its
orbital notation.
? What do you think the arrows represent?
Vocabulary!
Orbital Notation: a notation that shows the
distribution of electrons in the quantum model of the
atom. The electrons are indicated by arrows.
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Look at the following 2p orbital.
? Why is an “up” arrow added to each of the 2p suborbitals before the
second arrow is added? (Hint!: Think about what you learned
about how to add electrons to p suborbitals earlier in this lesson.)
Vocabulary!
Hund’s Rule: each suborbital within an orbital is filled with
one electron before an additional electron is added.
Notice that each suborbital contains arrows pointed up and down.
The different directions of the arrows indicate that the electrons
have opposite spins.
Vocabulary!
Pauli Exclusion Principle: The two electrons in each
suborbital spin in opposite directions. Opposite spinning
electrons are indicated by up and down arrows.
? Use the electron configurations below to draw the orbital
notations for each atom.
1s22s22p63s2
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1s22s22p2
1s22s22p63s23p4
1s22s22p63s23p64s2
d and f orbitals have very complex shapes. Look at the orbital notations
for the d and f orbitals shown below.
?
What is the maximum number of electrons that can fill a d orbital?
?
What is the maximum number of electrons that can fill an f
orbital?
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Important!
Look at the handout titled “The Periodic Table and Orbitals”.
This handout shows how certain areas of the periodic table correspond to
the different types of orbitals.
The colored areas or “blocks” of the periodic table indicate
the location of the last electron added to the atom.
? For each of the following atoms, use the periodic table to
identify which orbital was filled by the atom’s last electron.
Iron (Fe)
_____________
Sodium (Na)
_____________
Bromine (Br)
_____________
Uranium (U)
_____________
Your teacher has created a large version of the periodic table on
the floor.
The periodic table can be used to determine the order of orbital filling.
Watch as your teacher demonstrates how to use the periodic
table to write the
for the element
silver (Ag), by walking along the periodic table rows.
? Record the electron configuration for Ag below.
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