Chemistry Chapter 10 Flashcards
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Questions and Answers

Which scientist developed a model that can be used to predict the structure of a molecule?

  • Joseph Proust
  • John Dalton
  • Ernest Rutherford
  • G.N.Lewis (correct)

    • Which atom has a Lewis structure with an octet?

  • Cl
  • Na
  • Mg
  • Ar (correct)

    • In a Lewis structure, a dash drawn between two atoms represents _______________.

    a shared electron pair

    Which of the following atoms would most likely be terminal in a Lewis structure?

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

    Which of the following descriptions best describes the type of electrons used to write a Lewis structure?

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

    Which of the following is an exception to the octet rule?

    <p>SF6</p> Signup and view all the answers

    Which of the following symbols are used to illustrate commonalities between two or more resonance structures?

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

    How many resonance structures exist for the formate ion, HCO2−?

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

    Which of these molecules or ions exhibit resonance?

    <p>O3 and CO32-</p> Signup and view all the answers

    Construct an orbital diagram to show the electron configuration for a neutral magnesium atom, Mg.

    <p>1s2, 2s2, 2p6, 3s2</p> Signup and view all the answers

    To form a stable ion, will magnesium gain or lose electrons? How many electrons?

    <p>Will lose two electrons</p> Signup and view all the answers

    Match each ion with the noble gas whose electron configuration it shares.

    <p>He = Li+ and Be2+ Ne = O2-, Na+, and N3- Ar = Cl-, Ca2+, and S2-</p> Signup and view all the answers

    How many electrons are transferred between the cation and anion to form the ionic bond in one formula unit of each compound?

    <p>1 electron: KBr, LiF, and NaCl; 2 electrons: BaS and CaO</p> Signup and view all the answers

    Which nonmetals could form an ionic compound with magnesium with the formula MgX2 (where X represents the nonmetal)?

    <p>Possible: F, Br, and Cl; Not possible: N, S, and O</p> Signup and view all the answers

    Use Lewis theory to determine the formula for the compound that forms from Al and S.

    <p>Al2S3</p> Signup and view all the answers

    Use Lewis theory to determine the formula for the compound that forms from Na and S.

    <p>Na2S</p> Signup and view all the answers

    Use Lewis theory to determine the formula for the compound that forms from Sr and Se.

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

    Use Lewis theory to determine the formula for the compound that forms from Ba and F.

    <p>BaF2</p> Signup and view all the answers

    Use the Lewis model to predict the correct formula for the compound that forms between Ca and Br.

    <p>CaBr2</p> Signup and view all the answers

    How many total valence electrons are in the Lewis structure of NO3−?

    <p>24</p> Signup and view all the answers

    Determine the electron geometry of N2O (oxygen is terminal).

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

    Determine the molecular geometry of N2O (oxygen is terminal).

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

    Determine the electron geometry of SO2.

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

    Determine the molecular geometry of SO2.

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

    Determine the electron geometry of H2S.

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

    Determine the molecular geometry of H2S.

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

    Determine the electron geometry of PF3.

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

    Determine the molecular geometry of PF3.

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

    CO2−3

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

    ClO−2

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

    NO−3

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

    NH+4

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

    What is the molecular geometry of N2O (Nitrogen is the central atom)?

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

    What is the molecular geometry of PBr3?

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

    Which bond is polar?

    <p>A bond between H and Cl</p> Signup and view all the answers

    Which molecule is polar?

    <p>SCl2</p> Signup and view all the answers

    If a molecule has polar bonds, is the molecule itself polar?

    <p>If a molecule has polar bonds, the molecule can be either polar or nonpolar.</p> Signup and view all the answers

    Why?

    <p>The two requirements of a polar molecule are: the molecule must have polar bonds and the polar bonds must be distributed asymmetrically, otherwise they cancel out.</p> Signup and view all the answers

    How do you determine the number of electrons that go into the Lewis structure of a molecule?

    <p>Add up the valence electrons from each atom that is forming the molecule.</p> Signup and view all the answers

    What happens if you try to mix a polar liquid with a nonpolar one?

    <p>They will separate to form two distinct regions.</p> Signup and view all the answers

    Use the Lewis model to explain why the compound that forms between hydrogen and sulfur has the formula H2S.

    <p>Each H atom in a compound can contribute 1 valence e−, a S atom contributes 6 valence e−. When H2S forms, each H atom shares their 1e− with S and in doing so has achieved a stable duet.</p> Signup and view all the answers

    Would you expect HS to be stable?

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

    Would you expect H3S to be stable?

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

    If all of the electron groups around a central atom are bonding groups (that is, there are no lone pairs), what is the molecular geometry for two electron groups?

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

    If all of the electron groups around a central atom are bonding groups (that is, there are no lone pairs), what is the molecular geometry for three electron groups?

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

    If all of the electron groups around a central atom are bonding groups (that is, there are no lone pairs), what is the molecular geometry for four electron groups?

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

    Indicate which of the electrons in the electron configuration are shown in the Lewis structure.

    <p>1s22s22p63s23p64s23d104p65s1−−−</p> Signup and view all the answers

    Indicate which of the electrons in the electron configuration are shown in the Lewis structure.

    <p>1s22s22p63s23p64s23d104p6−−−</p> Signup and view all the answers

    Electron groups: 2. Bonding groups: 2. Lone pairs: 0.

    <p>Angle: 180</p> Signup and view all the answers

    Bonding groups: 3. Lone pairs: 0.

    <p>Electron geometry: Trigonal planar</p> Signup and view all the answers

    Bonding groups: 2. Lone pairs: 1.

    <p>Electron geometry: Trigonal planar</p> Signup and view all the answers

    Bonding groups: 4. Lone pairs: 0.

    <p>Angle: 109.5</p> Signup and view all the answers

    Bonding groups: 3. Lone pairs: 1.

    <p>Molecular: Trigonal pyramidal</p> Signup and view all the answers

    Bonding groups: 2. Lone pairs: 2.

    <p>Molecular: Bent</p> Signup and view all the answers

    How many bonding electrons are in the Lewis structure of N2?

    <p>6</p> Signup and view all the answers

    How many bonding electrons are in the Lewis structure of carbon monoxide, CO?

    <p>6</p> Signup and view all the answers

    How many valence electrons are in the nitrate ion?

    <p>24</p> Signup and view all the answers

    The correct Lewis structure for BF3 would be exactly:

    <p>no double bonds</p> Signup and view all the answers

    Which of the following compounds have resonance structures?

    <p>O3</p> Signup and view all the answers

    The VSEPR theory predicts that the angle between the central carbon atom and the two oxygen atoms in CO2 measures 180°.

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

    What is the angle between electron groups in the linear electron geometry?

    <p>180</p> Signup and view all the answers

    When you have 4 electron groups and none of them are lone pairs, the molecular geometry is trigonal pyramidal.

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

    What is the molecular geometry if you have 4 single bonds around the central atom?

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

    What is the electron geometry if you have 3 electron groups around the center atom?

    <p>trigonal planar</p> Signup and view all the answers

    What is the molecular geometry of CCl4?

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

    The electron geometry and the molecular geometry of ammonia (NH3) are, respectively:

    <p>tetrahedral, trigonal pyramidal</p> Signup and view all the answers

    The elements with the highest electronegativity values tend to be found in the:

    <p>upper right-side of the periodic table.</p> Signup and view all the answers

    Which molecule listed below has a polar covalent bond?

    <p>H2O</p> Signup and view all the answers

    Which molecule listed below has a nonpolar covalent bond?

    <p>H2</p> Signup and view all the answers

    Which molecule listed below is a polar molecule?

    <p>HCN, NH3, and H2O</p> Signup and view all the answers

    Which of the following statements are TRUE about the BF3 molecule?

    <p>BF3 has a trigonal planar molecular geometry. BF3 is nonpolar. BF3 violates the octet rule for the central atom.</p> Signup and view all the answers

    Consider the following electronegativity values: H = 2.1, Cl = 3.0, F = 4.0. Which molecule below would you expect to have the more polar bond?

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

    The electronegativity value for Mg is 1.2 and the value for O is 3.5. Based on these values, what type of bond is expected for a compound formed between Mg and O?

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

    Electronegativity Difference

    <p>2.0 +</p> Signup and view all the answers

    CBr4

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

    H2CO

    <p>trigonal planar</p> Signup and view all the answers

    CS2

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

    BH3

    <p>trigonal planar</p> Signup and view all the answers

    Study Notes

    G.N. Lewis and Lewis Structures

    • G.N. Lewis developed a model for predicting molecular structures.
    • Lewis structures use symbols to represent atoms, with dots for valence electrons.
    • A dash between atoms indicates a shared electron pair.

    Valence Electrons and Octet Rule

    • Valence electrons are the electrons involved in chemical bonding.
    • Noble gases typically have a complete octet, contributing to their stability (e.g., Ar has an octet).
    • Exceptions to the octet rule include molecules like SF6.

    Resonance Structures

    • Resonance occurs when more than one valid Lewis structure can be drawn for a molecule.
    • The symbol ↔ illustrates shared characteristics between multiple resonance structures.
    • The formate ion (HCO2−) has 2 resonance structures.

    Electron and Molecular Geometry

    • Electron geometry considers bonding and lone pairs around a central atom.
    • For two electron groups: linear geometry (180° angle).
    • For three electron groups: trigonal planar geometry (120° angle).
    • For four electron groups: tetrahedral geometry (109.5° angle).

    Bonding and Ions

    • Ionic compounds form from the transfer of electrons between metals and nonmetals.
    • Magnesium typically loses two electrons to form a stable ion.
    • Common ionic compounds include Na2S and BaF2.
    • Elements with high electronegativity often form polar bonds, as seen in H2O and HF.

    Polar vs. Nonpolar Molecules

    • Polar molecules have an uneven distribution of charge due to their molecular structure and bonds.
    • Nonpolar molecules, like H2, have an even charge distribution.
    • Geometry plays a crucial role in determining whether a molecule is polar or nonpolar.

    Molecular Shapes

    • Molecular geometry determines physical properties and reactivity.
    • Examples of molecular geometries include:
      • NH3: Trigonal pyramidal
      • H2S: Bent
      • CO2: Linear
      • CF4: Tetrahedral

    Electronegativity and Bonding Types

    • Electronegativity differences determine bond types:
      • Pure covalent (0-0.4), polar covalent (0.4-2.0), and ionic (2.0+).
    • Compounds formed from Mg and O are expected to be ionic due to their significant electronegativity difference.

    Summary of Notable Compounds

    • Ozone (O3) exhibits resonance structures.
    • BF3 is nonpolar with trigonal planar geometry and violates the octet rule.
    • The molecule HCN and others like NH3 and H2O are polar due to their structure and electronegativity differences.

    Important Concepts in Lewis Structures

    • When counting electrons for Lewis structures, sum the valence electrons from all atoms involved.
    • Mixing polar and nonpolar liquids results in separation into distinct regions rather than forming a homogenous solution.
    • Stable compounds can form despite differing electron configurations, emphasizing understanding of valence electrons and molecular geometries.

    VSEPR Theory

    • VSEPR (Valence Shell Electron Pair Repulsion) theory predicts molecular shapes based on repulsion between electron groups.
    • Molecules with no lone pairs around a central atom exhibit clear geometric arrangements (linear, trigonal planar, tetrahedral).

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