1.
Get out your notes
2.
Wait quietly

1.
Aufbau Principle
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Each electron MUST occupy the lowest energy orbital available first
2.
Pauli Exclusion Principle
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A maximum of 2 electrons can occupy a single orbital, but only if the electrons have opposite spins
3.
Hund’s Rule
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Single electrons with the same spin must occupy each equal energy orbital before additional electrons with opposite spins can occupy those same orbitals

Each electron MUST occupy the lowest energy level and sublevel available first
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Determine the order of energy levels, sub-levels, and the orbitals within the sub-levels
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Energy levels are in the order of the periods down the periodic table
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Order: 1, 2, 3, 4, 5, 6, and 7
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Sub-levels: are in the order of s, p, d, and f

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Notice that d and f sub-levels are “behind” s and p sub-levels

Pauli Exclusion Principle
A maximum of 2 electrons can occupy a single orbital, but only if the electrons have opposite spins

Remember the amount of orbitals in each sub-level

S-sublevel = 1 orbital = 2 electrons
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P-sublevel = 3 orbitals = 6 electrons
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D-sublevel = 5 orbitals = 10 electrons
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F=sublevel = 7 orbitals = 14 electrons
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Each energy level holds a set amount of electrons:
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1 st energy level = 1 sublevel and 1 orbital = max 2 electrons
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2 nd & 7 th energy level = 2 sublevels and 4 orbitals = max 8 electrons
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3 rd & 6 th energy level = 3 sublevels and 9 orbitals = max 18 electrons
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4 th – 5 th energy levels = 4 sublevels and 16 orbitals = max 32 electrons
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Remember that d and f sublevels are behind s and p

Single electrons with the same spin must occupy each equal energy orbital before additional electrons with opposite spins can occupy those same orbitals
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Orbital Notation:

Shows the electrons in an orbital and their spin
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S- 1 orbital, p- 3 orbitals, d – 5orbitals, and f – 7 orbitals
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Lines/boxes represent the orbitals
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The number of the energy level and its sublevel are written below the line

Uses up and down arrows to represent the electrons and their spins
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Example: Lithium – 1s 2 2s 1
_________ _________
1s 2s

Hund’s Rule
Orbital Notation

Let’s Try Nitrogen:

1s 2 2s 2 2p 3
___________
1s
_____________
2s
__________ ___________ ___________
2p
*This is called an orbital diagram/notation


What is Sulfur’s electron configuration?
________________________________________________________

What is Sulfur’s orbital notation?
*Remember:
S- 1 orbital, p- 3 orbitals, d – 5orbitals, and f – 7 orbitals

Your Turn:
Complete these in your notes

Write the orbital diagrams for the following elements:
Manganese
Potassium
Gallium


The electrons that determine the chemical properties of an element
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The electrons in the highest (outermost) energy level
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How do we know what is the highest/outermost energy level?

The electron configuration for Chlorine is:
1s 2 2s 2 2p 6 3s 2 3p 5
• The outermost energy level is the 3 rd energy level
• Chlorine has 7 valence electrons (2 + 5 = 7)


How many valence electrons are found in the following atoms?
Element Electron Configuration # of Valence Electrons
Sodium
Carbon
Gallium
Oxygen
Fluorine

Valence Electrons
THERE IS AN EASIER WAY!!!!

Lewis Dot Structure
A model that uses electron-dot structures to show how electrons are arranged in molecules.

Shows the valence electrons around the element symbol

What is an element symbol?

Aluminum =

Aluminum has _____ valence electrons

Imagine aluminum symbol with a box around it
Al
*Each side of the box can only hold 2 electrons
*Put 1 dot (to represent 1 electron) on each side before adding a second dot to that side of the box – Pauli’s Exclusion Principle
So the final product looks like this: Al

How many valence electrons does Sulfur have? ______
S

Your turn:
Complete these in your notes

Draw the Lewis Dot Structure for the following elements:
Element Symbol and number of valence electrons
Lewis Dot Structure
Lithium
Nitrogen
Calcium
Bromine
Carbon
Selenium

Work on your homework: Page 7 in packet and prelab
REMEMBER:
LAB TOMORROW YOU MUST BE DRESSED IN LAB
ATTIRE

Closed shoes

Long pants (no skin, not even ankles)

NO baggie sleeves

Hair pulled back