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# CP5.2-electrons

## on Nov 11, 2010

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## CP5.2-electronsPresentation Transcript

• Chapter 5: Electrons in Atoms
Section 2:Electron Arrangement in Atoms
• Apply the aufbau principle, the Pauli exclusion principle, and Hund’s Rule to generate electron configurations and spin diagrams;
Explain that there can be exceptions to the normal rules for electron configurations; and
Draw modified Bohr diagrams for atoms
Student will be able to:
Energy level
Sublevel
Orbital
Spin
Where do electrons live?
• State
• Town
• Street
• House
Need a system for electron addresses...
• Energy levels are numbered(1, 2, 3...)
Each energy level adds one more sublevel (letters)
Each sublevel adds two more orbitals
Sublevels and orbitals
• Sublevels addressed by the number of their energy level and letter of sublevel
Example: 1s, 2s, 2p, 3s, 3p, 3d
Still two more parts to address (orbital and spin)...
Electron configuration: arrangement of electrons in an atom in its ground state
Orbital diagram: illustrates arrangement and spin of electrons
Keeping track of all the sublevels
• Aufbau principle: electrons occupy orbitals of lowest energy first
Electrons (like some students) are lazy
Orbitals in same sublevel are same energy
Rules for Electron Configurations
• Pauli Exclusion Principle
Orbital can hold maximum of two electrons
(Two per seat on the bus)
If two electrons in an orbital, must be opposite spins
Two possible spins: up and down
Rules for Electron Configurations
• Hunds Rule
Orbitalsin same sublevel are same energy
Electrons fill orbitals of same energy so they maximize same spin
Students don’t pair up in a seat until they have to
Rules for electron configurations
• One electron for every proton
Periodic table arranged by atomic number
Typewriter method: start at H, read left to right, and stop at the element you’re configuring
Putting the rules to use...
• Further down the table...
La starts 4f sublevel
Comes after 6s and before 5d
Lu is actually 5d1
Ac starts 5f sublevel
Comes after 7s and before 6d
Lr is actually 6d1
Try some...
• There are exceptions to the normal rules for electron configurations
Based on stability
Just know that they exist, not how to do them
Just when you learn the rules...
• Atom drawn with nucleus in center and one ring for each energy level
Electrons drawn as dots on the rings
Example: S
1s2, one ring, 2 dots
2s2, 2p6, one ring, 8 dots
3s2, 3p4, one ring, 6 dots
Bohr Diagrams
• Group electrons by sublevels
Show spins
Example: S
1s2
one ring, 2 arrows paired
2s2, 2p6
one ring, 2 arrows paired (s), 6 arrows paired (p)
3s2, 3p4
One ring, two arrows paired (s) four arrows with two paired (p)
“Modified” Bohr Diagrams
16 p
16n
• Apply the aufbau principle, the Pauli exclusion principle, and Hund’s Rule to generate electron configurations and spin diagrams?
Explain that there can be exceptions to the normal rules for electron configurations?
Draw modified Bohr diagrams for atoms?
Can you…?
• Page 135 & 136, 8-13
Homework