Resonance Structures in Chemistry
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Questions and Answers

What is a characteristic of a more important resonance structure?

  • Adjacent atoms have similar formal charges
  • Atoms have high formal charges
  • Adjacent atoms do not have similar formal charges (correct)
  • Electronegative atoms bear positive formal charges

    • What is a condition for a resonance structure to be more important?

  • Formal charges are high
  • Number of unpaired electrons is inconsistent with the magnetic property
  • Electronegative atoms bear positive formal charges
  • Formal charges are close to zero (correct)

    • What is a factor that determines the importance of a resonance structure?

  • Electronegativity of atoms (correct)
  • Molecular geometry
  • Number of unpaired electrons
  • Bonding between atoms

    • What is the purpose of calculating formal charges?

    <p>To evaluate the importance of resonance structures</p> Signup and view all the answers

    What is a characteristic of a neutral molecule?

    <p>Formal charges are close to zero</p> Signup and view all the answers

    Which of the following factors does not affect the importance of a resonance structure?

    <p>Bonding energy</p> Signup and view all the answers

    What is the purpose of drawing resonance structures?

    <p>To evaluate the importance of resonance structures</p> Signup and view all the answers

    What determines the magnetic property of a molecule?

    <p>Number of unpaired electrons</p> Signup and view all the answers

    What determines the preferred resonance structure of an element?

    <p>The number of formal charges</p> Signup and view all the answers

    What is the general rule for elements in the third period and beyond?

    <p>They prefer a structure that obeys the octet rule</p> Signup and view all the answers

    What is a characteristic of the given structure?

    <p>It has fewer formal charges</p> Signup and view all the answers

    What is the relationship between formal charges and resonance structures?

    <p>A structure with fewer formal charges is preferred</p> Signup and view all the answers

    Why is structure (b) considered the most important?

    <p>Because the negative charge is on the more electronegative oxygen atom.</p> Signup and view all the answers

    What is the conditions under which an expanded octet is preferred?

    <p>When it bears fewer formal charges</p> Signup and view all the answers

    What is a characteristic of a resonance structure that is preferred?

    <p>It bears fewer formal charges</p> Signup and view all the answers

    Which of the following is true about structure (c)?

    <p>It has a larger separation of formal charges.</p> Signup and view all the answers

    What is the charge on the sulfate ion?

    <p>2–</p> Signup and view all the answers

    How many oxygen atoms are bonded to the central S atom in the sulfate ion?

    <p>4</p> Signup and view all the answers

    Which of the following is a characteristic of the sulfate ion?

    <p>It has a negative charge.</p> Signup and view all the answers

    What is the source of the information about the sulfate ion?

    <p>Chang, 2010</p> Signup and view all the answers

    What is the molecular structure of ClF3?

    <p>T-shaped</p> Signup and view all the answers

    What is the hybridization of the central atom in ClF3?

    <p>sp3d</p> Signup and view all the answers

    What is the number of bond pairs in ClF3?

    <p>3</p> Signup and view all the answers

    What is the number of lone pairs on the central atom in ClF3?

    <p>2</p> Signup and view all the answers

    Is ClF3 a polar or nonpolar molecule?

    <p>Polar</p> Signup and view all the answers

    What is the shape of the molecule ClF3?

    <p>T-shaped</p> Signup and view all the answers

    What is the reason for the increase in London forces with molar mass?

    <p>The molecules have more electrons, and dispersion forces increase in strength with the number of electrons</p> Signup and view all the answers

    What is the relationship between the number of electrons in a molecule and its melting point?

    <p>The melting point increases as the number of electrons in the molecule increases</p> Signup and view all the answers

    What is the trend observed in the boiling points of hydrogen compounds of Group 14?

    <p>The boiling point increases as the molar mass increases</p> Signup and view all the answers

    Why do larger atoms have a more easily disturbed electron distribution?

    <p>Because their outer electrons are less tightly held by the nuclei</p> Signup and view all the answers

    What is the relationship between the molar mass of a molecule and its electron distribution?

    <p>The electron distribution is more easily disturbed at higher molar masses</p> Signup and view all the answers

    Which of the following compounds has the highest boiling point?

    <p>SnH4</p> Signup and view all the answers

    What happens to the strength of dispersion forces as the number of electrons in a molecule increases?

    <p>The strength of dispersion forces increases</p> Signup and view all the answers

    Why do compounds with larger molar mass tend to have higher melting points?

    <p>Because they have more electrons and increased dispersion forces</p> Signup and view all the answers

    Study Notes

    Resonance Structures

    • A resonance structure is more important when adjacent atoms do not have similar formal charges.
    • Electronegative atoms bearing negative formal charges make a resonance structure more important.
    • Formal charges on atoms being close to zero for neutral molecules makes a resonance structure more important.
    • The number of unpaired electrons being consistent with the magnetic property of the species makes a resonance structure more important.

    Sample Problem 1: Nitrous Oxide

    • Draw three resonance structures for the molecule nitrous oxide (NNO).
    • Structure (b) is the most important because the negative charge is on the more electronegative oxygen atom.
    • Structure (c) is the least important because it has a larger separation of formal charges and the positive charge is on the more electronegative oxygen atom.

    Sample Problem 2: Sulfate Ion

    • Draw a Lewis structure for the sulfate ion (SO42–) in which all four O atoms are bonded to the central S atom.
    • The structure involves an expanded octet on S but may be considered more plausible because it bears fewer formal charges.

    General Rule for Elements

    • A resonance structure that obeys the octet rule is preferred over one that involves an expanded octet but bears fewer formal charges.

    Sample Problem 3: ClF3

    • Draw the Lewis structure of ClF3 and classify as polar or nonpolar.

    Intermolecular Forces

    • London forces usually increase with molar mass because molecules with larger molar mass tend to have more electrons, and dispersion forces increase in strength with the number of electrons.
    • Larger molar mass often means a bigger atom whose electron distribution is more easily disturbed because the outer electrons are less tightly held by the nuclei.
    • As expected, melting point increases as the number of electrons in the molecule increases.
    • Hydrogen compounds of Group 14 follow the trend of increasing boiling point with increasing molar mass.

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    Description

    This quiz covers resonance structures in chemistry, including factors that make them more important and how adjacent atoms and electronegative atoms affect formal charges.

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