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8.2: Covalent Bonding and Lewis Structures

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    Exercise \(\PageIndex{1}\)

    Name each molecule.

    1. What homonuclear diatomic molecule(s) have single bonds?  That is, both atoms are the same element (A-A or B-B, not A-B)
    2. What homonuclear diatomic molecule(s) have double bonds?
    3. What homonuclear diatomic molecule(s) have triple bonds?
    4. How many electrons are in the valence shell of nitrogen?
    Answer a

    H2, F2, Cl2, Br2, I2 

    Answer b

    O2 

    Answer c

    N2​​​​​​​ 

    Answer d

    5

     

     

    Exercise \(\PageIndex{2}\)

     

    1. What is the octet rule?
    2. What atom can never have an octet, and why?
    3. What group of the periodic table forms stable molecules with 6 electrons in its valence shell?
    4. Atoms of what periods can not have an expanded octet?
    Answer a

    Atoms in a molecule tend to have 8 electrons that reside in 4 orbitals.  These may be lone pairs (localized on the atom) or bonding pairs (shared with another nucleous)

    Answer b

    Hydrogen, as there is only one orbital in its valence shell, the 1s orbital​​​​​​ 

    Answer c

    Group IIIA

    Answer d

    the first and second period, as there are no d orbitals.  The first period only has a 1s orbital, while the second has 2s and three 2p

     

    Exercise \(\PageIndex{3}\)

     

    1. How many electrons are in a double bond?
    2. How many electrons are in a triple bond?
    3. What group of the periodic table forms stable molecules with 6 electrons in its valence shell?
    4. Carbon and sulfur are in group IVA and both have 4 valence electrons in their valence shell.  Why can sulfur have an expanded octet, but carbon can not?
    Answer a

    4

    Answer b

    6​​​​​​ 

    Answer c

    Group IIIA

    Answer d

    Carbon is in the second period and so there are only 4 orbitals in the valence shell (2s and three 2p) and thus it can only have 8 electrons, while sulfur is in the third period and has 8 orbitals (one 3s, threee 3p and five 3d), and so it can hold more electrons and have an expanded octet.

     

    Exercise \(\PageIndex{1}\)

    Which of the following statements is/are CORRECT?

    1. Chemical reactions result in the gain, loss, or rearrangement of valence electrons.
    2. For main group elements, the number of valence electrons equals eight minus the element’s group number.
    3. Core electrons are not involved in bonding or in chemical reactions.

    a. 1 only        b. 2 only        c. 3 only        d. 1 and 3        e. 1, 2, and 3

    Answer

    d. 1 and 3

    Exercise \(\PageIndex{2}\)

    The given representation of an atom is called the _____.

    P.png

    1. a Lewis dot structure.
    2. an ion.
    3. a structural formula.
    4. an electrostatic potential map.
    5. an ionic bond.
    Answer

    a. a Lewis dot structure.

    Exercise \(\PageIndex{3}\)

    In the Lewis formula for sulfur dioxide, SO2, the number of lone pairs of electrons around the sulfur atom is

    Answer

    1. 

    Exercise \(\PageIndex{4}\)

    What is the total number of electrons (both lone and bond pairs) in the Lewis structure of SO42-?

    Answer

    32

    Exercise \(\PageIndex{5}\)

    How many valence electrons are present in the Lewis formula for the chlorite ion, Cl2–?

    Answer

    20

    Exercise \(\PageIndex{6}\)

    Which of the following molecules or ions are isoelectronic: SO3, NF3, NO3–, CO32–?

    Answer

    SO3, NO3– and CO32–

    Exercise \(\PageIndex{7}\)

    Which of the following has a Lewis structure similar to OCS?

    a. NH2−        b. O3        c. CO2        d. SO2        e. ClO2−   

    Answer

    c. CO2

    Exercise \(\PageIndex{8}\)

    The correct Lewis structure for Cl2CO is (the 2 Cl's and the O are bound to the C and not to each other):

    a. a..png        b. b..png        c. c..png        d. d..png        e. None of these

    Answer

    d.  d..png

    Exercise \(\PageIndex{9}\)

    Which of the following is the Lewis electron dot structure for carbon monoxide?

    a. 13a.png        b. 13b.png        c. 13c.png        d. 13d.png        e. 13e.png

    Answer

    a. 13a.png  

     

    Exercise \(\PageIndex{10}\)

     Which of the following will often have a Lewis dot structure with 6 electrons in the valence orbital?

    B, Be, Al, Mg, C, S, Cl

    Answer

    B and Al

     

    Exercise \(\PageIndex{10}\)

     Which of the following will often have a Lewis dot structure with 4 electrons in the valence orbital?

    B, Be, Al, Mg, C, S, Cl

    Answer

    Be, Mg

     

    Exercise \(\PageIndex{10}\)

     Which of the following will often have a Lewis dot structure with 12 electrons in the valence orbital?

    B, Be, Al, Mg, C, S, Cl

    Answer

    S

     

    Exercise \(\PageIndex{10}\)

     Which of the following will often have a Lewis dot structure with 10 electrons in the valence orbital?

    B, Be, Al, Mg, C, P, S 

    Answer

    P

     

    8.2: Covalent Bonding and Lewis Structures is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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