Transcript Chapter 4 Section 3 Electron Configurations Lesson Starter • The electron configuration of carbon is 1s22s22p2. • An electron configuration describes the arrangement of electrons.

Chapter 4
Section 3 Electron Configurations
Lesson Starter
• The electron configuration of carbon is 1s22s22p2.
• An electron configuration describes the arrangement
of electrons in an atom.
• The integers indicate the main energy level of each
orbital occupied by electrons.
• The letters indicate the shape of the occupied
orbitals.
• The superscripts identify the number of electrons in
each sublevel.
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Homework:
Chapter 4 review questions pg. 124-126
#1, 3-11, 13-41, (1-41 except #2 & 12)
due by Tuesday.
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Chapter 4
Section 3 Electron Configurations
Objectives
• List the total number of electrons needed to fully
occupy each main energy level.
• State the Aufbau principle, the Pauli exclusion
principle, and Hund’s rule.
• Describe the electron configurations for the atoms
of any element using orbital notation, electronconfiguration notation, and, when appropriate,
noble-gas notation.
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4.3
Electron Arrangement in Atoms
If this rock were to tumble over,
it would end up at a lower
height. It would have less
energy than before, but its
position would be more stable.
You will learn that energy and
stability play an important role
in determining how electrons
are configured in an atom.
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Chapter 4
Section 3 Electron Configurations
Electron Configurations
• The arrangement of electrons in an atom is known
as the atom’s electron configuration.
• The lowest-energy arrangement of the electrons
for each element is called the element’s groundstate electron configuration.
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Chapter 4
Visual Concepts
Electron Configuration
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4.3
Electron Arrangement in
Atoms
>
Electron Configurations
Electron Configurations
What are the three rules for writing the
electron configurations of elements?
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4.3
Electron Arrangement in
Atoms
>
Electron Configurations
The ways in which electrons are arranged in
various orbitals around the nuclei of atoms are
called electron configurations.
Three rules—the Aufbau principle, the
Pauli exclusion principle, and Hund’s
rule—tell you how to find the electron
configurations of atoms.
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4.3
Electron Arrangement in
Atoms
>
Electron Configurations
Aufbau Principle
According to the Aufbau principle, electrons
occupy the orbitals of lowest energy first. In the
Aufbau diagram below, each box represents an
atomic orbital.
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Chapter 4
Visual Concepts
Aufbau Principle
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4.3
Electron Arrangement in
Atoms
>
Electron Configurations
Pauli Exclusion Principle
• According to the Pauli exclusion
principle, no two electrons in the same
atom can have the same set of four
quantum numbers.
According to the Pauli exclusion principle, an
atomic orbital may describe at most two
electrons. To occupy the same orbital, two
electrons must have opposite spins; that is, the
electron spins must be paired.
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Chapter 4
Section 3 Electron Configurations
Relative Energies of Orbitals
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Chapter 4
Visual Concepts
Pauli Exclusion Principle
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4.3
Electron Arrangement in
Atoms
>
Electron Configurations
Hund’s Rule
• According to Hund’s rule, orbitals of
equal energy are each occupied by one
electron before any orbital is occupied
by a second electron, and all electrons
in singly occupied orbitals must have
the same spin state.
*just stated differently..
Hund’s rule states that electrons occupy
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orbitals of the same energy in a way that makes
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Chapter 4
Section 3 Electron Configurations
Representing Electron Configurations
Orbital Notation
• An unoccupied orbital is represented by a line, with
the orbital’s name written underneath the line.
• An orbital containing one electron is represented as:

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Chapter 4
Section 3 Electron Configurations
Representing Electron Configurations,
continued
Orbital Notation
• An orbital containing two electrons is represented as:

• The lines are labeled with the principal quantum
number and sublevel letter. For example, the orbital
notation for helium is written as follows:
He

1s
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Orbital Notation
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Chapter 4
Section 3 Electron Configurations
Representing Electron Configurations,
continued
Electron-Configuration Notation
• Electron-configuration notation eliminates the lines
and arrows of orbital notation.
• Instead, the number of electrons in a sublevel is
shown by adding a superscript to the sublevel
designation.
• The helium configuration is represented by 1s2.
• The superscript indicates that there are two electrons
in helium’s 1s orbital.
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Chapter 4
Visual Concepts
Reading Electron-Configuration Notation
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Chapter 4
Section 3 Electron Configurations
Representing Electron Configurations,
continued
Sample Problem A
The electron configuration of boron is 1s22s22p1.
How many electrons are present in an atom of
boron? What is the atomic number for boron?
Write the orbital notation for boron.
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Chapter 4
Section 3 Electron Configurations
Representing Electron Configurations,
continued
Sample Problem A Solution
The number of electrons in a boron atom is equal to
the sum of the superscripts in its electronconfiguration notation: 2 + 2 + 1 = 5 electrons. The
number of protons equals the number of electrons in
a neutral atom. So we know that boron has 5 protons
and thus has an atomic number of 5. To write the
orbital notation, first draw the lines representing
orbitals.
1s
2s
1 4 2 43
2p
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Chapter 4
Section 3 Electron Configurations
Representing Electron Configurations,
continued
Sample Problem A Solution, continued
Next, add arrows showing the electron locations.
The first two electrons occupy n = 1 energy level
and fill the 1s orbital.

1s
2s
1 4 2 43
2p
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Chapter 4
Section 3 Electron Configurations
Representing Electron Configurations,
continued
Sample Problem A Solution, continued
The next three electrons occupy the n = 2 main
energy level. Two of these occupy the lowerenergy 2s orbital. The third occupies a higherenergy p orbital.
  
1 4 2 43
1s
2s
2p
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Chapter 4
Section 3 Electron Configurations
Elements of the Second Period
• In the first-period elements, hydrogen and helium,
electrons occupy the orbital of the first main
energy level.
• According to the Aufbau principle, after the 1s
orbital is filled, the next electron occupies the s
sublevel in the second main energy level.
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Chapter 4
Section 3 Electron Configurations
Elements of the Second Period, continued
• The highest-occupied energy level is the electroncontaining main energy level with the highest
principal quantum number.
• Inner-shell electrons are electrons that are not in
the highest-occupied energy level.
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4.3
Electron Arrangement in
Atoms
>
Electron Configurations
Orbital Filling Diagram
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Models of the Atom
>
Atomic Orbitals
Click here for animation
Animation 5
Observe the characteristics of atomic orbitals.
ANIMATION TOOK A MINUTE TO LOAD. - This is a good animation
for how the orbitals fill up.
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Chapter 4
Section 3 Electron Configurations
Writing Electron Configurations
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Chapter 4
Section 3 Electron Configurations
Elements of the Third Period
•
After the outer octet is filled in neon, the next
electron enters the s sublevel in the n = 3 main
energy level.
Noble-Gas Notation
• The Group 18 elements (helium, neon, argon,
krypton, xenon, and radon) are called the noble
gases.
•
A noble-gas configuration refers to an outer
main energy level occupied, in most cases, by
eight electrons.
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Chapter 4
Section 3 Electron Configurations
Orbital Notation for Three Noble Gases
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Chapter 4
Visual Concepts
Noble-Gas Notation
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Chapter 4
Section 3 Electron Configurations
Elements of the Fourth Period
• The period begins by filling the 4s orbital, the
empty orbital of lowest energy.
• With the 4s sublevel filled, the 4p and 3d
sublevels are the next available vacant orbitals.
• The 3d sublevel is lower in energy than the 4p
sublevel. Therefore, the five 3d orbitals are next to
be filled.
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Chapter 4
Section 3 Electron Configurations
Orbital Notation for Argon and Potassium
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Chapter 4
Section 3 Electron Configurations
Elements of the Fifth Period
• In the 18 elements of the fifth period, sublevels fill
in a similar manner as in elements of the fourth
period.
• Successive electrons are added first to the 5s
orbital, then to the 4d orbitals, and finally to the 5p
orbitals.
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Chapter 4
Section 3 Electron Configurations
Sample Problem B
a. Write both the complete electron-configuration
notation and the noble-gas notation for iron, Fe.
b. How many electron-containing orbitals are in an atom
of iron? How many of these orbitals are completely
filled? How many unpaired electrons are there in an
atom of iron? In which sublevel are the unpaired
electrons located?
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Chapter 4
Section 3 Electron Configurations
Sample Problem B Solution
a. The complete electron-configuration notation of iron is
1s22s22p63s23p63d64s2. Iron’s noble-gas notation is
[Ar]3d64s2.
b. An iron atom has 15 orbitals that contain electrons.
They consist of one 1s orbital, one 2s orbital, three 2p
orbitals, one 3s orbital, three 3p orbitals, five 3d orbitals,
and one 4s orbital.
Eleven of these orbitals are filled, and there are four
unpaired electrons.
They are located in the 3d sublevel.
 


 .
The notation 3d6 represents 3d
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Chapter 4
Section 3 Electron Configurations
Sample Problem C
a. Write both the complete electron-configuration
notation and the noble-gas notation for a
rubidium atom.
b. Identify the elements in the second, third, and
fourth periods that have the same number of
highest-energy-level electrons as rubidium.
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Chapter 4
Section 3 Electron Configurations
Sample Problem C Solution
a. 1s22s22p63s23p63d104s24p65s1, [Kr]5s1
b. Rubidium has one electron in its highest
energy level (the fifth). The elements with the
same outermost configuration are,
in the second period, lithium, Li;
in the third period, sodium, Na;
and in the fourth period, potassium, K.
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Electron Arrangement in
Atoms
>
Electron Configurations
Simulation 2
Fill atomic orbitals to build the ground state of
several atoms.
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Practice Problems
for Conceptual Problem 1.1
Problem Solving 5.9 Solve Problem 9
with the help of an interactive guided
tutorial.
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4.3
Electron Arrangement in
Atoms
>
Exceptional Electron Configurations
Exceptional Electron Configurations
Why do actual electron configurations
for some elements differ from those
assigned using the aufbau principle?
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Electron Arrangement in
Atoms
>
Exceptional Electron Configurations
Some actual electron configurations
differ from those assigned using the
aufbau principle because half-filled
sublevels are not as stable as filled
sublevels, but they are more stable than
other configurations.
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4.3
Electron Arrangement in
Atoms
>
Exceptional Electron Configurations
Exceptions to the aufbau
principle are due to subtle
electron-electron
interactions in orbitals with
very similar energies.
Copper has an electron
configuration that is an
exception to the aufbau
principle.
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5.2 Section Quiz.
Assess students’ understanding of
the concepts in Section
5.2.
Continue to:
-or-
Launch:
Section Quiz
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4.3 Section Quiz.
1. Identify the element that corresponds to the
following electron configuration: 1s22s22p5.
a. F
b. Cl
c. Ne
d. O
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4.3 Section Quiz.
2. Write the electron configuration for the atom N.
a. 1s22s22p5
b. 1s22s22p3
c. 1s22s1p2
d. 1s22s22p1
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4.3 Section Quiz.
3. The electron configurations for some
elements differ from those predicted by the
aufbau principle because the
a. the lowest energy level is completely filled.
b. none of the energy levels are completely
filled.
c. half-filled sublevels are less stable than
filled energy levels.
d. half-filled sublevels are more stable than
`
some other arrangements.
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Online Self-Check Quiz
Complete the online Quiz and record answers.
Ask if you have any questions about your
answers.
click here for online Quiz 4.3
(10 questions)
You must be in the “Play mode” for the
slideshow for hyperlink to work.
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VIDEOS FOR ADDITIONAL INSTRUCTION
Additional Videos for Section 4.3: Electron Configuration
•Electron Configuration (3:53)
•Exceptions to Electron Configuration (2:58)
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SCI LINKS FOR CHAPTER
Additional Student SCI LINKS for CHAPTER 4
The NSTA-sponsored SciLinks Web site contains links to accurate and upto-date science
information on the Internet. Just click on the button below to go to the
SciLinks site at
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you want to
research. The following is a list of the SciLinks codes for this chapter.
Chapter 4: Arrangement of Electrons in Atoms
Topic: Electromagnetic Spectrum
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SciLinks code: HC60482
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