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Chemistry Notes. Electron Configurations. Electron Configurations. Studying the arrangement of electrons in atoms helps one understand chemical activity. From an electron configuration you can determine: Most stable electron arrangement Charge Bonding patterns Etc.

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Chemistry notes

Chemistry Notes

Electron Configurations


Electron configurations
Electron Configurations

  • Studying the arrangement of electrons in atoms helps one understand chemical activity.

  • From an electron configuration you can determine:

    • Most stable electron arrangement

    • Charge

    • Bonding patterns

    • Etc.


Electron configurations1
Electron Configurations

Electron Configurations: Shows the Principle Energy Levels, the sublevels and the number of electrons in those sublevels.

Examples of electron configurations:

  • H  1s1

  • He  1s2

  • Li  1s22s1

  • O  1s22s22p4



Electron configurations3
Electron Configurations

Rule to remember when writing an electron configuration for a certain atom:

  • Auf Bau Principle – The lowest energy levels fill first in atoms

    • Some Energy Levels do overlap

      • In atoms a 4s level will fill before a 3d level because the 4s sublevel has a lower energy than the 3d.


Electron configurations4
Electron Configurations

  • Notice: the 4s is lower in energy than the 3d sublevel, therefore, it fills first.


Electron configurations5
Electron Configurations

Start at the top of the arrow, go down. Once you are at the head of the arrow go to the top of the next. Repeat until you have reached the desired number of electrons.

Using this diagram can help you understand how to write the correct electron configuration for each atom.


Electron configurations6
Electron Configurations

EX: Ag has 47 electrons

  • Fill sublevels unit they add up to 47.

  • Remember how many electrons can go in each sublevel.

    1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d9

s = 2

p = 6

d = 10

f = 14

Notice: the last sublevel only contains 9 (not 10) electrons


Electron configurations7
Electron Configurations

  • Another Ex:  Titanium has 22 electrons

    Ti: 1s2 2s2 2p6 3s2 3p6 4s2 3d2

2 6 10 14


Electron configurations8
Electron Configurations

  • Here is a similar diagram for EC


Electron configurations9
Electron Configurations

  • EC can be abbreviated  a noble gas configuration (seen below).

Notice: [Ar] represents the EC of Argon


Orbital filling diagrams
Orbital Filling Diagrams

An orbital diagram give more detailed information than an electron configuration.

  • Boxes or blanks are used to represent orbitals.

  • Arrows represent electrons.

    • Upward-pointing arrows represent electrons with +1/2 spin

    • Downward-pointing arrows represent electrons with -1/2 spin

  • Like EC but arrows are used instead of #’s



Orbital filling diagrams2
Orbital Filling Diagrams

Rules to remember when writing an orbital filling diagram for a certain atom:

  • Hund’s Rule – each orbital gets one electron before any get two

    • EX: Nitrogen  each 2p orbital gets on e- before any get 2 e-.


Orbital filling diagrams3
Orbital Filling Diagrams

  • Hund’s Rule (cont.)

    Notice that the 2p electrons are shown as…

    rather than.

This is WRONG!!!


Orbital filling diagrams4
Orbital Filling Diagrams

Rules to remember when writing an orbital filling diagram for a certain atom:

  • Pauli Exclusion Principle – electrons in the same orbital must spin opposite directions.

    • This is why one arrow is drawn up and one is drawn down.


Orbital filling diagrams5
Orbital Filling Diagrams

Examples of An Orbital Filling Diagrams



Summary
Summary

Be able to…

  • Explain what EC and OFD are

  • Write and EC

    • Recall the Auf Bau Principle

  • Write and OFD

    • Recall Hund’s Rule

    • Recall the Pauli Exclusion Principle


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