Pauli Exclusion, Hund’s Rule, Orbital
Diagrams, Valence Electrons,
Unpaired Electrons
• Objective
– Today I will be able to:
• Explain the behavior of electrons based on Pauli’s exclusion
Principle and Hund’s Rule
• Illustrate the location of an electron by drawing an orbital diagram
• Determine the number of unpaired electrons in an atom
• Identify the location of valance electrons in an atom
• Evaluation/ Assessment
– Informal assessment – student responses when reviewing
electron configuration problems, orbital diagrams and
valence electrons. Listening to group interactions on
practice sheets
– Formal Assessment – collecting and analyzing responses to
electron configuration worksheet 2 and the where is the
electron lab. Reviewing responses to the exit ticket
Lesson Sequence
• Warm – Up
• Explain: principles, rules and
diagrams of electron
configurations
• Elaborate: Students complete
orbital diagrams worksheet
• Evaluate: Students will draw
orbital diagrams on the board
and explain their answers
(informal assessment)
• Explain: Valance Electrons
Notes
• Elaborate: Students complete
a valance electrons worksheet
• Evaluate: Students will share
responses to the worksheet
• Exit Ticket
Warm - Up
Write the electron configuration
for the following elements:
• Magnesium
• Iron
• Arsenic
What is the abbreviated configuration
for Sulfur?
Objectives
• Today I will be able to:
– Explain the behavior of electrons based on Pauli’s
exclusion Principle and Hund’s Rule
– Illustrate the location of an electron by drawing an
orbital diagram
– Determine the number of unpaired electrons in an
atom
– Identify the location of valance electrons in an
atom
Homework
• STEM Fair Conclusion Due Tuesday
Agenda
• Warm – Up
• Collect Flame Test Lab
• Notes Pauli Exclusion Principle, Hund’s Rule,
Orbital Diagrams
• Orbital Diagram Practice
• Review Practice as a class
• Valence Electron Notes
• Valance Electron Practice
• Exit Ticket
Electron Configuration Rules and
Principles
Aufbau Principle
• Electrons fill in lower energy levels before
filling in higher energy levels
Pauli Exclusion Principle
•
•
•
•
An orbital can hold a max of 2 eTo occupy the same orbital, they must spin
in opposite directions
If 2 e- occupy an orbital, they are said to be
“paired”
If only 1 e- is present in an orbital, it is
“unpaired”
Pauli Exclusion Principle
Hund’s Rule
• e- occupy orbitals so that a max number
of unpaired e- result
• More stable arrangement
Orbital Diagram
• Shows the electrons in their sublevels
• Represented with arrows
Orbital Diagram
1s
2s
2px
2py 2pz
H
↑
He
↑↓
C
↑↓
↑↓
↑
↑
Ne
↑↓
↑↓
↑↓
↑↓
↑↓
Complete the Electron Configuration
and Orbital Diagram Practice
Worksheet
Review the Electron Configuration
and Orbital Diagram Practice
Worksheet
Valence Electron Notes
Valence Electrons
• Electrons in the outermost energy level
• Determines the number of electrons an
atom gains, loses, or shares
• These are the electrons that are
involved in bonding
Valence Electrons (skip)
• Write the electron configuration for
oxygen
• 1s2 2s2 2p4
• Oxygen has six valence electrons (2s2 and
2p4)
Valence Electrons (skip)
• Write the electron configuration for
potassium
• 1s2 2s2 2p6 3s2 3p6 4s1
• Potassium has 1 valence electron (4s1)
Valence Electrons
•
•
•
•
Exceptions are the d and f sublevels! Use
the number of electrons in the last s sublevel
(and the p sublevel, if available)
Write the electron configuration for Bromine
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
Bromine has seven valence electron (4s2 and
4p5)
Foreshadowing: Octet Rule
• Most atoms want 8 electrons in their
outermost level OR full s and/or p
sublevels
• Atoms will form bonds to achieve the
desired amount of electrons
• Atoms are most stable when they have a
full outer shell
Complete Valence Electrons
Worksheet
Review Valence Electrons
Worksheet as a class
Exit Ticket
• For the element Chlorine:
– Write the electron configuration
– Write the abbreviated electron configuration
– Draw an orbital diagram
• Explain why you drew the electrons in the location of
the orbital's that you did
– Determine the number of valence electrons