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Chemistry LibreTexts

Solutions

  • Page ID
    11087
  • For each molecule on the worksheet, the Lewis Dot Structure, the number of valence electrons, the electron arrangement (E.A.) and the molecular geometry (M.G.) are given, respectively. To see a larger view of the Lewis Dot Structure, point at the molecule, right click on the mouse and go to 'View image'.

    Lewis Dot works best for covalent compounds of group A elements, though Lewis Dot Structures can explain electron transfer in ionic compounds. By following the rules below, the Lewis Dot Structure can be written for covalent compounds and some polyatomic ions.

    1. Count the total number of valence electrons, adjust for charge if an ion. Add one electron for each negative charge, subtract one electron for each positive charge.
    2. Place a pair of electrons between the central atom (usually written first) and each of the outer atoms.
    3. Complete the octet of the outer atoms (except H, which needs only 2 electrons).
    4. Place extra electrons, if any, on the central atom in pairs.
    5. If the central atom does not have a complete octet, share extra electrons from the outer atoms until the central atom and the outer atoms have a complete octet. Note: halides do not form double bonds.

    PF5 40 electrons
    tbp
    tbp
    CS2 16 electrons
    linear
    linear
    BrO3- 26 electrons
    Td
    trigonal pyr.
    NH4+
    8 electrons
    Td
    Td
    SCl4 34 electrons
    tbp
    see-saw
    BrF5 42 electrons
    Oh
    square pyr.
    BF3
    24 electrons
    trigonal planar
    trigonal planar
    SCl6 48 electrons
    Oh
    Oh
    PH3
    8 electrons
    Td
    trigonal pyr.
    NF3
    26 electrons
    Td
    trigonal pyr.
    SO42-
    32 electrons
    Td
    Td
    CO32- 24 electrons
    trigonal planar
    trigonal planar
    SiCl4 32 electrons
    Td
    Td
    ClO3- 26 electrons
    Td
    trigonal pyr.
    CH2O 12 electrons
    trigonal planar
    trigonal planar
    NO3-
    24 electrons
    trigonal planar
    trigonal planar
    O3
    18 electrons
    trigonal planar
    bent
    CCl4 32 electrons
    Td
    Td
    AlH3
    6 electrons
    trigonal planar
    trigonal planar
    SO2 18 electrons
    trigonal planar
    bent
    SO3 24 electrons
    trigonal planar
    trigonal planar
    CO
    10 electrons
    linear
    linear
    CHCl3 26 electrons
    Td
    Td
    BrF3 28 electrons
    tbp
    T-shaped
    H2S
    8 electrons
    Td
    bent
    I3- 22 electrons
    tbp
    linear
    H3O+
    8 electrons
    Td
    trigonal pyr.