1. Chapter 5 Electrons In Atoms 5.2 Electron Arrangement in Atoms
5.1 Revising the Atomic Model
5.2 Electron Arrangement
in Atoms
5.3 Atomic Emission Spectra and
the Quantum Mechanical Model
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2. Electron Configurations
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Begin Atomic Orbitals Assignment
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3. Electron Configurations
Describes location of electrons in an atom
Looks like…
Titanium: 1s22s22p63s23p64s23d2
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4. Electron Configurations
Aufbau Principle
Aufbau principle: electrons occupy orbitals of lowest energy first.
Each box represents an atomic orbital.
Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p
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5. Electron Configurations
Pauli Exclusion Principle
Each orbital can only hold 2 electrons.
To occupy the same orbital, two electrons must have opposite spins
An orbital containing paired electrons is written as .
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6. Electron Configurations
Aufbau Principle
Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p
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7. Electron Configurations
Hund’s rule
Orbitals of the same energy level must be occupied by 1 electron before it can be occupied by two electrons.
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8. Electron Configurations
Hund’s Rule
Three electrons would occupy three orbitals of equal energy as follows.
Electrons then occupy each orbital so that their spins are paired with the first electron in the orbital.
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9. Quantum Numbers
The building = atom Apartment Floors = Energy Levels (shells) Specific Apartments = Orbitals (subshells) Residents = Electrons

10. Electron Configurations
Increasing energy 6s 5s 4s 3s 2s 1s 6p 5p 5d 4p 4d 4f 3p 3d 2p
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11. Writing Electron Configurations
Sample Problem 5.1
Writing Electron Configurations
The atomic number of phosphorus is 15. Write the electron configuration of a phosphorus atom.
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12. Writing Electron Configurations
Sample Problem 5.1
Writing Electron Configurations
The atomic number of phosphorus is 15. Write the electron configuration of a phosphorus atom.
1s22s22p63s23p3.
Note: The superscripts add up to the number of electrons.
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13. The Quantum Mechanical Model
Do Now
Write the electron configurations for
Phosphorus
Arsenic
Antimony
Bismuth
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14. Noble Gas Configurations
Sample Problem 5.1
Noble Gas Configurations
Write the symbol of the previous noble gas in brackets.
Continue your electron configuration using the row after the noble gas.
Examples
Cl: [Ne] 3s2 3p5
Os: [Xe] 6s2 4f14 5d6
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15. Electron Configurations in Groups
Blocks of Elements
Each period on the periodic table corresponds to a principal energy level.
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16. END OF 5.2
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