Lewis structure

(noun)

Formalism used to show the structure of a molecule or compound, in which shared electrons pairs between atoms are indicated by dashes. Non-bonding, lone pairs of electrons must also be shown.

Related Terms

  • Lewis symbols
  • Lewis
  • principal energy levels
  • valence level
  • Lewis Symbols for Atoms
  • Lewis Symbols
  • valence level
  • lewis electron-dot structure
  • exceptions to the octet rule
  • covalent bond
  • octet rule
  • valence electrons
  • group
  • Noble Gases
  • Lewis symbol

Examples of Lewis structure in the following topics:

  • Lewis Structures for Polyatomic Ions

    • The Lewis structure of an ion is placed in brackets and its charge is written as a superscript outside of the brackets, on the upper right.
    • The total number of electrons represented in a Lewis structure is equal to the sum of the numbers of valence electrons in each individual atom.
    • Non-valence electrons are not represented in Lewis structures.
    • Lewis structures for polyatomic ions are drawn by the same methods that we have already learned.
    • When the Lewis structure of an ion is written, the entire structure is placed in brackets, and the charge is written as a superscript on the upper right, outside of the brackets.
  • Formal Charge and Lewis Structure

    • In particular, chemists use Lewis structures (also known as Lewis dot diagrams, electron dot diagrams, or electron structures) to represent covalent compounds.
    • Non-valence electrons are not represented when drawing the Lewis structures.
    • In the Lewis structure, carbon should be double-bonded to both oxygen atoms.
    • Lewis structures can also be drawn for ions.
    • Sometimes multiple Lewis structures can be drawn to represent the same compound.
  • Introduction to Lewis Structures for Covalent Molecules

    • The former, known as a 'Lewis dot diagram,' indicates a pair of shared electrons between the atomic symbols, while the latter, known as a 'Lewis structure,' uses a dash to indicate the pair of shared electrons that form a covalent bond.
    • The resulting molecule that is formed is F2, and its Lewis structure is F—F.
    • We have looked at how to determine Lewis structures for simple molecules.
    • The Lewis structure for carbon dioxide, CO2, is a good example of this.
    • Predict and draw the Lewis structure of simple covalent molecules and compounds
  • Resonance

    • Lewis dot structures can be drawn to visualize the electrons and bonds of a certain molecule.
    • However, for some molecules not all the bonding possibilities cannot be represented by a single Lewis structure; these molecules have several contributing or "resonance" structures.
    • Each contributing resonance structure can be visualized by drawing a Lewis structure; however, it is important to note that each of these structures cannot actually be observed in nature.
    • For example, the nitrate ion, NO3-, has more than one valid Lewis structure.
    • Because atoms with electric charges are not as stable as atoms without electric charges, these resonance structures will contribute less to the overall resonance structure than a structure with no charges.
  • Representing Valence Electrons in Lewis Symbols

    • Lewis symbols use dots to visually represent the valence electrons of an atom.
    • Lewis symbols (also known as Lewis dot diagrams or electron dot diagrams) are diagrams that represent the valence electrons of an atom.
    • Lewis structures (also known as Lewis dot structures or electron dot structures) are diagrams that represent the valence electrons of atoms within a molecule.
    • These Lewis symbols and Lewis structures help visualize the valence electrons of atoms and molecules, whether they exist as lone pairs or within bonds.
    • Lewis symbols for atoms are combined to write Lewis structures for compounds or molecules with bonds between atoms.
  • Writing Lewis Symbols for Atoms

    • The Lewis symbol for an atom depicts its valence electrons as dots around the symbol for the element.
    • In order to write the Lewis symbol for an atom, you must first determine the number of valence electrons for that element.
    • Lewis symbols for the elements depict the number of valence electrons as dots.
    • Once you can draw a Lewis symbol for an atom, you can use the knowledge of Lewis symbols to create Lewis structures for molecules.
    • In the Lewis symbol, the electrons are depicted as two lone pair dots.
  • Trihalides: Boron-Halogen Compounds

    • Trihalides adopt a planar trigonal structure and are Lewis acids.
    • Boron undergoes halogenation to form trihalides with the molecular structure BX3, as in the following:
    • The trihalides form planar trigonal structures and are Lewis acids because they readily form adducts with electron-pair donors, which are called Lewis bases.
    • Such measurements have revealed the following sequence for the Lewis acidity: BF3 < BCl3 < BBr3 (in other words, BBr3 is the strongest Lewis acid).
    • Boron (III) trifluoride structure, BF3, showing the "empty" boron p orbital in pi-type coordinate covalent bonds.
  • Lewis Acid and Base Molecules

    • Lewis bases are electron-pair donors, whereas Lewis acids are electron-pair acceptors.
    • A Lewis acid is defined as an electron-pair acceptor, whereas a Lewis base is an electron-pair donor.
    • A Lewis base, therefore, is any species that donates a pair of electrons to a Lewis acid.
    • Under the Lewis definition, hydroxide acts as the Lewis base, donating its electron pair to H+.
    • We first look at the Bronsted-Lowry theory, and then describe Lewis acids and bases according to the Lewis Theory.
  • Metal Cations that Act as Lewis Acids

    • Transition metals can act as Lewis acids by accepting electron pairs from donor Lewis bases to form complex ions.
    • The modern-day definition of a Lewis acid, as given by IUPAC, is a molecular entity—and corresponding chemical species—that is an electron-pair acceptor and therefore able to react with a Lewis base to form a Lewis adduct; this is accomplished by sharing the electron pair furnished by the Lewis base.
    • However, metal ions such as Na+, Mg2+, and Ce3+ often form Lewis adducts upon reacting with a Lewis base.
    • Ligands create a complex when forming coordinate bonds with transition metals ions; the transition metal ion acts as a Lewis acid, and the ligand acts as a Lewis base.
    • Usually, metal complexes can only serve as Lewis acids after dissociating from a more weakly bound Lewis base, often water.
  • Acid-Base Reactions

    • Structurally related acid-base pairs, such as {H-A and A:(–)} or {B:(–) and B-H} are called conjugate pairs.
    • Lewis bases are also Brønsted bases; however, many Lewis acids, such as BF3, AlCl3 and Mg2+, are not Brønsted acids.
    • Carbocations are also Lewis acids, as the reverse reaction demonstrates.
    • A terminology related to the Lewis acid-base nomenclature is often used by organic chemists.
    • Here the term electrophile corresponds to a Lewis acid, and nucleophile corresponds to a Lewis base.
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