CHEM 1411 Chapter 6 Flashcards
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Questions and Answers

Which of the following Lewis structures are invalid? (Select all that apply)

  • NO3 (correct)
  • OF2 (correct)
  • CO2 (correct)
  • F2 (correct)

    • What is the Lewis structure for HF?

    Single bond between H and F; F has three lone pairs.

    What is the Lewis structure for H2O?

    Single bonds among all three atoms; O has two lone pairs.

    What is the Lewis structure for HNO?

    <p>Double bond between O and N, single bond between N and H; O has two lone pairs; N has one lone pair.</p> Signup and view all the answers

    Order the following elements by electronegativity from most electronegative to least electronegative.

    <p>O, N, Al, Na, Rb</p> Signup and view all the answers

    Which molecules cannot be adequately described by a single Lewis structure?

    <p>CO3^2- and O3</p> Signup and view all the answers

    Add formal charges to each resonance form of HCNO. Which structure is favored?

    <p>A: (triple bond between N and O, single bonds between all other atoms) -2 on C; +1 on N, +1 on O.</p> Signup and view all the answers

    What is the Lewis structure for CO?

    <p>C and O both have one lone pair, bonded by a triple bond. C is -1, and O is +1.</p> Signup and view all the answers

    Assign formal charges to each atom in the resonance forms of SCN-. Which resonance structure contributes the most?

    <p>C: (S with 2 lone pairs and a double bond to C) 0 on S and C, -1 on N.</p> Signup and view all the answers

    Identify the likely identity for X, Y, and Z in the structures provided.

    <p>A: Be, B: B, C: O</p> Signup and view all the answers

    What are the Lewis structures for SO2 obeying the octet rule?

    <p>O = S - O with +1 on S, -1 on O and O = S = O with double bonds among all.</p> Signup and view all the answers

    What is the Lewis structure for ClF2^-1?

    <p>F - Cl - F with both F having 3 lone pairs, Cl has 3 lone pairs.</p> Signup and view all the answers

    What is the Lewis structure for XeF2?

    <p>F - Xe - F with all atoms having three lone pairs each.</p> Signup and view all the answers

    What bond is expected to be the most polar?

    <p>C - F</p> Signup and view all the answers

    Indicate the direction of polarity of the bonds: C______ - O______

    <ul> <li> <ul> <li></li> </ul> </li> </ul> Signup and view all the answers

    Indicate the direction of polarity of the bonds: O______ - Cl______

    <ul> <li> <ul> <li></li> </ul> </li> </ul> Signup and view all the answers

    Indicate the direction of polarity of the bonds: O______ - F______

    <ul> <li> <ul> <li></li> </ul> </li> </ul> Signup and view all the answers

    Indicate the direction of polarity of the bonds: C______ - N______

    <ul> <li> <ul> <li></li> </ul> </li> </ul> Signup and view all the answers

    Indicate the direction of polarity of the bonds: Cl______ - C______

    <ul> <li> <ul> <li></li> </ul> </li> </ul> Signup and view all the answers

    Indicate the direction of polarity of the bonds: S______ - H______

    <ul> <li> <ul> <li></li> </ul> </li> </ul> Signup and view all the answers

    Indicate the direction of polarity of the bonds: S______ - Cl______

    <ul> <li> <ul> <li></li> </ul> </li> </ul> Signup and view all the answers

    Calculate the percent ionic character of a hypothetical molecule X-Y with a dipole moment of 1.15 D and a bond length of 151 pm.

    <p>15.9%</p> Signup and view all the answers

    Arrange the tripod-shaped molecules in order of decreasing dipole moment.

    <p>NH3, PH3, AsH3</p> Signup and view all the answers

    Arrange the bonds from most ionic to most covalent.

    <p>K-F, Ca-F, Br-F, Cl-F, F-F</p> Signup and view all the answers

    What are the Lewis formulas for the reactants and products of the hydrogen peroxide formation?

    <p>Reactant: OH with one lone pair and one solitary electron, Product: H2O2 with single bonds and lone pairs.</p> Signup and view all the answers

    Study Notes

    Lewis Structures and Resonance

    • Lewis structures depict the arrangement of electrons in molecules, highlighting shared and lone pairs.
    • Errors in Lewis structures can arise from wrong electron totals or octet-rule violations.
    • The nitrate ion (NO₃⁻) has three resonance forms, each involving shifting double bonds and specifying formal charges.

    Electronegativity and Bond Polarity

    • Electronegativity describes an atom's ability to attract electrons; the order from most to least electronegative: O > N > Al > Na > Rb.
    • The bond C-F is expected to be the most polar among various chemical bonds.
    • Polar covalent bonds can be marked with delta notation to indicate partial charges.

    Formal Charges and Molecular Geometry

    • Formal charges help determine the stability of different resonance structures.
    • For HCNO, structures can have various formal charges, influencing their favorability.
    • Xenon (Xe) can exceed the octet rule, forming stable structures like XeF₂.

    Molecular Shapes and Dipole Moments

    • Tripod-shaped molecules can be ranked by their dipole moments: NH₃ > PH₃ > AsH₃.
    • Percent ionic character quantifies the degree of ionic versus covalent character in a bond, with a formula based on dipole moment.

    Free Radicals and Bond Formation

    • Free radicals can combine to form stable molecules, such as hydrogen peroxide (H₂O₂), through the formation of new electron-pair bonds.
    • Lewis formulas for reactants and products emphasize nonbonding electrons, showcasing the transition from radicals to stable compounds.

    Special Compounds and Ions

    • Certain molecules, like CO₃²⁻ and ozone (O₃), cannot be represented accurately by a single Lewis structure due to resonance.
    • Polyhalide ion ClF₂⁻ contains single bonds, with the central atom (Cl) having three lone pairs, while both fluorine (F) atoms each possess three lone pairs as well.

    Summary of Bonding Characteristics

    • Arrange bonds according to their ionic character, with K-F being the most ionic and F-F being the most covalent.
    • Explore different molecular geometries and varying electron arrangements to better understand chemical bonding and molecular interaction dynamics.

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    Description

    Test your understanding of Lewis structures in CHEM 1411 Chapter 6 with these flashcards. Identify the errors in various Lewis structures and complete others by adding the correct number of electrons. This quiz is designed to enhance your comprehension of molecular geometry and bonding.

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