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3. To go to the higher
floors in a
building, we need
to use the stairs
starting from the
lowest step until
we reach the top.
How do we
associate this with
the distribution of
electrons in an
atom?
4. Learning Competency
● Write electron configuration of atoms.
● Draw orbital diagrams to illustrate the electron
configuration of the atom.
At the end of this lesson, the given enabling or enrichment
competency should be met by the students.
5. Learning Objectives
At the end of this lesson, the learner should be able to
do the following:
● Assign quantum numbers to electrons in an atom.
● Write the electron configuration of an atom.
● Draw orbital diagrams to represent the electron
configuration of the atom.
6. Try it!
Warm-Up
Balloons? Orbitals!
Step 1 Secure some balloons and inflate them.
Step 2
Create the following models:
● 1s and 2s orbitals
● set of 2p orbitals
● set of 3d orbitals
7. Learn about It
The electron configuration is simply a description of how
electrons are distributed in an atom. An electron configuration
follows the spdf notation.
Electron Configuration
8. Learn about It
Aufbau Principle
● Atomic orbitals are filled from the
lowest energy to the highest energy as
shown in the diagram below:
Rules in Writing Electron Configuration
9. Learn about It
Hund’s Rule
● Every orbital in the same subshell must be filled singly
before being paired.
● All electrons in singly occupied orbitals should have a
parallel spin.
Rules in Writing Electron Configuration
10. Learn about It
Pauli’s Exclusion Principle
● No two electrons can have the exact same set of quantum
numbers. Electrons in the same orbital must have opposite
spins.
Rules in Writing Electron Configuration
11. Learn about It
The shorthand way of writing electron configuration is also
called the noble gas electron configuration.
1. Determine the atomic number of the element in the
periodic table. For neutral atoms, the atomic number (Z) is
equal to the number of electrons.
2. Fill up the maximum number of electrons per orbital
according to the Aufbau principle.
Writing Longhand Electron Configuration of
Neutral Atoms
12. Learn about It
The shorthand way of writing electron configuration is also
called the noble gas electron configuration.
3. Determine the nearest preceding noble gas. Substitute the
electron configuration of the noble gas by writing the
element symbol of the noble gas in brackets.
4. Retain the atomic orbitals that are not part of electron
configuration of the noble gas.
Writing Longhand Electron Configuration of
Neutral Atoms
13. Try It!
Write the longhand electron configuration of
argon. Draw its orbital diagram.
14. Try It! (Answer)
Write the longhand electron configuration of
argon. Draw its orbital diagram.
The longhand electron configuration is
1s2 2s2 2p6 3s2 3p6.
15. Key Points
● Electrons are specifically distributed in the orbitals using rules
of electron configuration.
● The electron configuration follows the spdf notation, where
the principal quantum numbers come into play.
16. Key Points
● The electron configuration of a neutral atom follows the
principles of Aufbau, Hund’s, and Pauli’s.
○ The Aufbau principle states that the electrons are filled up
from the lowest energy orbital to the highest energy
orbital.
○ Hund’s rule states that degenerate orbitals in a specific
subshell are filled with electrons one at a time first, with all
spins parallel to one another.
○ Pauli’s exclusion principle states that no two electrons in
the same atom can have the same set of quantum
numbers.
17. Key Points
● The electron configuration can be written in other ways aside
from the complete, longhand version. The shorthand notation
focuses only on the noble gas core and the valence orbitals,
while the orbital diagram notation focuses on electron
distribution in degenerate orbitals by illustrating the electron
spins of the electrons through arrows.
18. Check Your Understanding
Complete the table by indicating what is
needed.
Element Shorthand notation Longhand notation
[Kr] 5s2
1s22s22p4
1s22s22p63s23p64s23d8
An element with 20
electrons
An element with Z = 15
19. Bibliography
Chang, Raymond and Kenneth A. Goldsby. 2016. Chemistry. New York, NY: McGraw-Hill
Education.
Georgia State University. “Hund’s Rules”. Accessed June 21, 2017. http://hyperphysics.phy-
astr.gsu.edu/hbase/Atomic/Hund.html.
Silberberg, Martin. 2009. Chemistry: The Molecular Nature of Matter and Change, 5th edition.
New York, NY: McGraw-Hill Education.
University of Oregon. “Pauli Exclusion Principle”. Accessed June 21, 2017.
http://abyss.uoregon.edu/~js/glossary/pauli_exclusion_principle.html.
Whitten, Kenneth W. 2006. General Chemistry. Thomson Brooks/Cole.
