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4: Compounds and Molecules

  • Page ID
    279974
  • Chemical Compounds

    Exercise \(\PageIndex{1.a}\)

    Using the periodic table, predict whether the following chlorides are ionic or covalent: KCl, NCl3, ICl, MgCl2, PCl5, and CCl4.

    Answer

    Ionic: KCl, MgCl2

    Covalent: NCl3, ICl, PCl5, CCl4

     

    Exercise \(\PageIndex{1.b}\)

    Using the periodic table, predict whether the following chlorides are ionic or covalent: KCl, NCl3, ICl, MgCl2, PCl5, and CCl4.

    Answer

    Ionic: KCl, MgCl2

    Covalent: NCl3, ICl, PCl5, CCl4

    Exercise \(\PageIndex{1.c}\)

    For each of the following compounds, state whether it is ionic or covalent. If it is ionic, write the symbols for the ions involved:

    1. NF3
    2. BaO
    3. IBr
    4. Na2O
    Answer a

    covalent

    Answer b

    ionic, Ba2+, O−2

    Answer c

    covalent

    Answer d

    ionic, Na+, O−2

     

    Molecular Compounds

    Exercise \(\PageIndex{2.a}\)

    Explain why the symbol for an atom of the element oxygen and the formula for a molecule of oxygen differ.

    Answer

    The symbol for the element oxygen, O, represents both the element and one atom of oxygen. A molecule of oxygen, O2, contains two oxygen atoms; the subscript 2 in the formula must be used to distinguish the diatomic molecule from two single oxygen atoms.

     

     

    Ionic Compounds and Formulas

    Exercise \(\PageIndex{3.a}\)

    For each of the following pairs of ions, write the formula of the compound they will form:

    1. Ca2+, S2−
    2. \(NH_{4}^{+}\), \(SO_{4}^{2-}\)
    3. Al3+, Br
    4. Na+, \(HPO_{4}^{2-}\)
    5. Mg2+, \(PO_{4}^{3-}\)
    Answer a

    CaS

    Answer b

    (NH4)2SO4

    Answer c

    AlBr3

    Answer d

    Na2HPO4

    Answer e

    Mg3(PO4)2

     

     

     

    Polyatomic Ions

     

     

    Nomenclature

    Exercise \(\PageIndex{5.a}\)

    Name the following compounds:

    1. CsCl
    2. BaO
    3. K2S
    4. BeCl2
    5. HBr
    6. AlF3
    Answer a

    cesium chloride

    Answer b

    barium oxide

    Answer c

    potassium sulfide

    Answer d

    beryllium chloride

    Answer e

    hydrogen bromide

    Answer f

    aluminum fluoride

    Exercise \(\PageIndex{5.b}\)

    Each of the following compounds contains a metal that can exhibit more than one ionic charge. Name these compounds:

    1. Cr2O3
    2. FeCl2
    3. CrO3
    4. TiCl4
    5. CoO
    6. MoS2
    Answer a

    chromium(III) oxide

    Answer b

    iron(II) chloride

    Answer c

    chromium(VI) oxide

    Answer d

    titanium(IV) chloride

    Answer e

    cobalt(II) oxide

    Answer f

    molybdenum(IV) sulfide

    Exercise \(\PageIndex{5.c}\)

    Write the formulas of the following compounds:

    1. rubidium bromide
    2. magnesium selenide
    3. sodium oxide
    4. calcium chloride
    5. hydrogen fluoride
    6. gallium phosphide
    7. aluminum bromide
    8. ammonium sulfate
    Answer a
    RbBr
    Answer b
    MgSe
    Answer c
    Na2O
    Answer d
    CaCl2
    Answer e
    HF
    Answer f
    GaP
    Answer g
    AlBr3
    Answer h
    (NH4)2SO4

    Exercise \(\PageIndex{5.d}\)

    Write the formulas of the following compounds:

    1. chlorine dioxide
    2. dinitrogen tetraoxide
    3. potassium phosphide
    4. silver(I) sulfide
    5. aluminum nitride
    6. silicon dioxide
    Answer a
    ClO2
    Answer b
    N2O4
    Answer c
    K3P
    Answer d
    Ag2S
    Answer e
    AlN
    Answer f
    SiO2

    Exercise \(\PageIndex{5.e}\)

    The following ionic compounds are found in common household products. Write the formulas for each compound:

    1. potassium phosphate
    2. copper(II) sulfate
    3. calcium chloride
    4. titanium dioxide
    5. ammonium nitrate
    6. sodium bisulfate (the common name for sodium hydrogen sulfate)
    Answer a
    K3PO4
    Answer b
    CuSO4
    Answer c
    CaCl2
    Answer d
    TiO2
    Answer e
    NH4NO3
    Answer f
    NaHSO4

     

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