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Chemistry LibreTexts

3.2: Lewis Dot Diagrams

  • Page ID
    235754
  • Skills to Develop

    • Write Lewis symbols for neutral atoms and ions

    Thus far, we have discussed the various types of bonds that form between atoms and/or ions. In all cases, these bonds involve the sharing or transfer of valence shell electrons between atoms. In this section, we will explore the typical method for depicting valence shell electrons and chemical bonds, namely Lewis symbols and Lewis structures.

    Lewis Symbols

    We use Lewis symbols to describe valence electron configurations of atoms and monatomic ions. A Lewis symbol consists of an elemental symbol surrounded by one dot for each of its valence electrons:

    Figure \(\PageIndex{1}\) shows the Lewis symbols for the elements of the third period of the periodic table. Electron dots are typically arranged in four pairs located on the four "sides" of the atomic symbol.

    Figure \(\PageIndex{1}\): Lewis symbols illustrating the number of valence electrons for each element in the third period of the periodic table.

    Lewis symbols can be used to illustrate the formation of cations from atoms, as shown here for sodium and calcium:

    imageedit_42_3965005021.jpg

    Likewise, they can be used to show the formation of anions from atoms, as shown here for chlorine and sulfur:

    imageedit_46_6318422358.jpg

    Figure \(\PageIndex{2}\) demonstrates the use of Lewis symbols to show the transfer of electrons during the formation of ionic compounds.

    Figure \(\PageIndex{2}\): Cations are formed when atoms lose electrons, represented by fewer Lewis dots, whereas anions are formed by atoms gaining electrons. The total number of electrons does not change.

    Summary

    Valence electronic structures can be visualized by drawing Lewis symbols (for atoms and monatomic ions) . Lone pairs, unpaired electrons, and single, double, or triple bonds are used to indicate where the valence electrons are located around the atom.

    Glossary

    Lewis symbol
    symbol for an element or monatomic ion that uses a dot to represent each valence electron in the element or ion

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