Chemistry Chapter 13: Structure and Shape
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Questions and Answers

What is the first step in drawing a Lewis diagram?

  • Join atoms by single bonds.
  • Place the least electronegative atom(s) in the center of the molecule or ion.
  • Calculate the total number of valence electrons. (correct)
  • Draw a tentative diagram.

    • What is the second step in drawing a Lewis diagram?

  • Place the least electronegative atom(s) in the center of the molecule or ion. (correct)
  • Join atoms by single bonds.
  • Calculate the total number of valence electrons.
  • Draw a tentative diagram.

    • What is the purpose of step 4 in drawing a Lewis diagram?

  • To calculate the number of valence electrons in the tentative diagram.
  • To compare the number of valence electrons in the tentative diagram with the actual number of valence electrons.
  • To remove a lone pair from the central and terminal atoms and replace them with an additional bonding pair.
  • All of the above. (correct)

    • What is the main goal of this chapter?

    <p>To learn about the structure and shape of molecules. (B)</p> Signup and view all the answers

    What is the difference between hydrocarbons and other organic compounds?

    <p>Hydrocarbons contain only carbon and hydrogen atoms, while other organic compounds contain other atoms as well. (A)</p> Signup and view all the answers

    What is the difference between alcohols, ethers, and carboxylic acids?

    <p>They differ in the functional group that they contain. (A)</p> Signup and view all the answers

    What is the central atom in the hydrogen carbonate ion, HCO3-

    <p>Carbon (B)</p> Signup and view all the answers

    How many valence electrons are there in the hydrogen carbonate ion, HCO3-

    <p>24 (C)</p> Signup and view all the answers

    What is the electron-pair geometry for a molecule with 3 regions of electron density surrounding the central atom?

    <p>Trigonal planar (D)</p> Signup and view all the answers

    What is the total number of electron pairs in the hydrogen carbonate ion, HCO3-

    <p>11 (C)</p> Signup and view all the answers

    What is the shape of the hydrogen carbonate ion, HCO3-, according to VSEPR theory?

    <p>Trigonal planar (D)</p> Signup and view all the answers

    What is the bond angle for a molecule with a linear electron-pair geometry?

    <p>180° (C)</p> Signup and view all the answers

    What is the electron-pair geometry of the hydrogen carbonate ion, HCO3-

    <p>Tetrahedral (D)</p> Signup and view all the answers

    Which of the following describes the molecular geometry of a molecule with two bonding regions and one lone pair of electrons?

    <p>Angular (C)</p> Signup and view all the answers

    What is the electron-pair angle in a tetrahedral geometry?

    <p>109.5 degrees (D)</p> Signup and view all the answers

    What is resonance?

    <p>The process of creating a molecule or ion by changing only the positions of the electrons (C)</p> Signup and view all the answers

    What is the bond angle for a molecule with a tetrahedral electron-pair geometry?

    <p>109.5° (D)</p> Signup and view all the answers

    What is the molecular geometry of a molecule with three bonding regions and no lone pairs?

    <p>Trigonal planar (B)</p> Signup and view all the answers

    What is a resonance hybrid?

    <p>The actual molecule or ion that is an average of the resonance structures (D)</p> Signup and view all the answers

    What are isomers?

    <p>Two compounds having the same molecular formulas but different structures (B)</p> Signup and view all the answers

    What type of line is used to represent an atom that is behind the plane of the page in a wedge-and-dash diagram?

    <p>Dashed line (D)</p> Signup and view all the answers

    What is VSEPR theory?

    <p>The idea that electron pairs repel each other (B)</p> Signup and view all the answers

    In a wedge-and-dash diagram, what does a wedge-shaped line represent?

    <p>An atom in front of the plane of the page (A)</p> Signup and view all the answers

    What is the first step in predicting the molecular geometry of a molecule?

    <p>Draw the Lewis diagram (A)</p> Signup and view all the answers

    What two factors are considered when determining the electron-pair geometry of a molecule?

    <p>Number of lone pairs and number of bonding pairs (B)</p> Signup and view all the answers

    Which of the following molecules would be considered a polar molecule?

    <p>CH2Cl2 (A), CHCl3 (D)</p> Signup and view all the answers

    Which of the following is NOT classified as an inorganic compound?

    <p>Hydrocarbons (D)</p> Signup and view all the answers

    What is the defining characteristic of an alkane?

    <p>Each carbon atom forms four single bonds. (B)</p> Signup and view all the answers

    Which functional group is characteristic of alcohols?

    <p>Hydroxyl group (C)</p> Signup and view all the answers

    Which of the following statements accurately describes carboxylic acids?

    <p>They are weak acids that only slightly ionize in water. (A)</p> Signup and view all the answers

    What is the molecular geometry of a molecule with three regions of electron density, one of which is a lone pair?

    <p>Trigonal pyramidal (A)</p> Signup and view all the answers

    What is the electron-pair geometry around a central atom with two lone pairs and two bonding regions?

    <p>Tetrahedral (A)</p> Signup and view all the answers

    Which of the following features can result in a nonpolar molecule?

    <p>All bonded atoms are identical (B)</p> Signup and view all the answers

    In a wedge-and-dash diagram, what does a dashed line represent?

    <p>A bond pointing away from the viewer (D)</p> Signup and view all the answers

    What is the molecular geometry of nitrogen trichloride, NCl3?

    <p>Trigonal pyramidal (A)</p> Signup and view all the answers

    How does a polar molecule behave in an electric field?

    <p>It aligns with the more electronegative atoms pointing towards the positive plate (C)</p> Signup and view all the answers

    Which of the following molecules will have a linear molecular geometry?

    <p>CO2 (D)</p> Signup and view all the answers

    What is the electron-pair geometry around the carbon atom in tetrafluoroethylene, C2F4?

    <p>Trigonal planar (B)</p> Signup and view all the answers

    What is the main factor that determines the electron-pair geometry around a central atom?

    <p>The number of regions of electron density around the central atom (C)</p> Signup and view all the answers

    Which of the following statements accurately describes a wedge-and-dash diagram?

    <p>It shows the arrangement of bonds and lone pairs around the central atom (B)</p> Signup and view all the answers

    Flashcards

    Lewis Diagram

    A representation showing all valence electrons in a molecule or ion.

    Electron-Pair Geometry

    The spatial arrangement of regions of electron density around a central atom.

    Molecular Geometry

    The 3D arrangement of atoms in a molecule, determined by electron-pair geometry.

    Wedge-and-Dash Diagram

    A 2D representation of a molecule that shows 3D connectivity with bonds.

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    Polar vs Nonpolar Molecules

    Polar molecules have a net dipole moment; nonpolar do not.

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    Organic Compounds

    Compounds primarily made of carbon, often including hydrogen.

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    Inorganic Compounds

    Compounds that typically do not contain carbon-hydrogen bonds.

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    Valence Electrons

    Electrons in the outermost shell of an atom, involved in bonding.

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    Central Atom

    The atom in a molecule that other atoms bond to, typically less electronegative.

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    Resonance Structures

    Different Lewis diagrams for the same molecule, differing only in electron positions.

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    Resonance Hybrid

    A representation of a molecule that is an average of multiple resonance structures.

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    Electron-Pair Repulsion

    The principle that electron pairs around a central atom repel each other and maximize distance.

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    VSEPR Theory

    Theory that predicts molecular shapes based on electron pair repulsion.

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    Electron-Pair Angle

    The angle formed between two electron pairs around a central atom.

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    Isomers

    Compounds that have the same molecular formula but different structural arrangements.

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    Tetrahedron

    A geometric shape with four triangular faces, common in molecular geometry.

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    Linear Electron-Pair Geometry

    Occurs with 2 regions of electron density, bond angle 180°.

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    Trigonal Planar Geometry

    Occurs with 3 regions of electron density, bond angle 120°.

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    Tetrahedral Geometry

    Occurs with 4 regions of electron density, bond angle 109.5°.

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    Bond Angle

    The angle between two adjacent bonds.

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    Regions of Electron Density

    Represents areas where electrons reside around a central atom (bonds + lone pairs).

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    Angular/Bent Molecular Geometry

    Occurs when there are 2 bonding and 1 lone pair electron regions.

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    Predicting Molecular Geometries

    A systematic approach using Lewis diagrams to determine geometry by counting electron density regions.

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    Polar molecules

    Molecules that have an uneven distribution of charges, resulting from asymmetry around an axis.

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    Hydrocarbons

    Compounds composed only of hydrogen and carbon atoms; includes alkanes, alkenes, and alkynes.

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    Alcohols

    Organic compounds that contain a hydroxyl group (-OH) which determines their chemical properties.

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    Ethers

    Compounds with two hydrocarbon groups bonded to a single oxygen atom.

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    Carboxylic Acids

    Compounds with a carboxyl group (-COOH), weak acids that ionize partially in water.

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    Trigonal Pyramidal

    A molecular geometry with three bonding regions and one lone pair.

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    Bent Molecular Geometry

    A molecular shape with two bonding regions and two lone pairs.

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    Conditions for Nonpolarity

    Central atom has no lone pairs and all bonded atoms are identical.

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    Study Notes

    Chapter 13: Structure and Shape

    • This chapter focuses on the structure and shape of molecules and polyatomic ions.

    • Key goals include drawing Lewis diagrams, describing electron-pair geometries, predicting molecular geometries, and drawing wedge-and-dash diagrams.

    • Determining if a molecule is polar or nonpolar and identifying polarity.

    • Distinguishing between organic and inorganic compounds, as well as hydrocarbons and other organic compounds. Differences in structure and geometry for various organic compound classes (alcohols, ethers, carboxylic acids).

    • A step-by-step process is outlined for drawing Lewis diagrams, including calculating valence electrons and ensuring octet completion.

    • Resonance structures are explored, representing equivalent Lewis diagrams where electrons are repositioned.

    • The actual molecule is a 'resonance hybrid,' a blend of the resonance structures. Isomers are also introduced: different molecules with the same molecular formula.

    • Valence Shell Electron Pair Repulsion (VSEPR) theory explains how electron pairs arrange themselves to maximize distance, influencing molecular shapes.

    • Electron-pair angles and specific geometries (linear, trigonal planar, tetrahedral) are presented based on the number of electron-pair regions around the central atom.

    • Tables and figures illustrate various molecular geometries for different numbers of regions of electron density (2, 3, and 4).

    • Wedge-and-dash diagrams are explained for illustrating 3D molecular structures.

    • Steps for predicting molecular geometries based on electron density around the central atom are given

    • Examples and exercises (like ammonia NH3 and hydrogen carbonate HCO3-) are provided to further illustrate the concepts.

    • Differences between organic and inorganic compounds are detailed.

    • Organic chemistry focuses on carbon compounds.

    • Alkane definition: Each carbon atom forms four single bonds.

    • Isomers and their structures (such as butane and pentane isomers) are described.

    • Hydroxyl (-OH), ethers, and carboxylic acids (-COOH) groups are part of specific classes of organic compounds.

    • Differences between alcohols, ethers, and carboxylic acids in terms of their structure and properties are shown.

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    Chapter 13 Structure and Shape PDF

    Description

    This quiz covers the essential concepts of molecular structure and shape from Chapter 13. You'll learn to draw Lewis diagrams, predict molecular geometries, and distinguish between polar and nonpolar molecules. The quiz also explores resonance structures and isomers, providing a thorough understanding of both organic and inorganic compounds.

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