Electron Configuration Anomalies


  • Some of the elements have electron configurations that differ slightly from what our general procedure would lead us to predict. Because a few of these elements are important elements, it is useful to know their actual electron configurations. Six of these are listed on the table below. 

     

    Unusual Electron Configurations

    Element

    Predicted Electron Configuration

    Actual Electron Configuration

    copper, Cu

    [Ar] 3d9 4s2

    [Ar] 3d10 4s1

    silver, Ag

    [Kr] 4d9 5s2

    [Kr] 4d10 5s1

    gold, Au

    [Xe] 4f14 5d9 6s2

    [Xe] 4f14 5d10 6s1

    palladium, Pd

    [Kr] 4d8 5s2

    [Kr] 4d10

    chromium, Cr

    [Ar] 3d4 4s2

    [Ar] 3d5 4s1

    molybdenum, Mo

    [Kr] 4d4 5s2

    [Kr] 4d5 5s1