Ch.7 - Covalent Bonding and Electron-Dot Structures
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- The graph shows how potential energy changes as a function of the distance between two atoms. (LO 7.2)
Problem 1
What is the length of the bond between the two atoms? (a) 3.4 angstroms (b) 3.8 angstroms (c) 6.0 angstroms (d) 8.0 angstroms
- Which molecule has the shortest carbon–oxygen bond? (LO 7.3, 7.9) (a) CH3OH (b) CO (c) CO2 (d) HCOOH
Problem 2
- The compounds below are paired with a type of bonding. Which type of bonding is incorrectly classified? (LO 7.5) (a) Rb2O (polar covalent) (b) SO2 (polar covalent) (c) O3 (nonpolar covalent) (d) KBr (ionic) (e) HF (polar covalent)
Problem 3
- Which compound is a solid at room temperature? (LO 7.8) (a) H2O (b) Na2S (c) SO3 (d) Cl2
Problem 5
Problem 10
Which of the following pairs represent resonance structures? (LO 7.13) (a)(b)(c)
Problem 11
The structure for the DNA base cytosine is shown.
Which of the following is not a resonance structure of cytosine? (LO 7.13) (a)
(b)
(c)
(d)
- What is the best prediction for the carbon–oxygen bond length in the carbonate anion, CO3 2-? (LO 7.14) Data for average carbon-oxygen bond lengths: (a) 143 pm (b) 132 pm (c) 121 pm (d) 118 pm
Problem 12
- Which is the best electron-dot structure for the thiosulfate ion (S2O3 2-) based on the rules of formal charge? (LO 7.16) (a) (b) (c) (d)
Problem 14
Problem 15
Use formal charge to select which resonance structure makes the largest contribution to the resonance hybrid. (LO 7.16) (a) Structure I (b) Structure II (c) Structure III (d) All structures are equivalent and make the same contri-bution to the resonance hybrid. (I)
(II)
(III)
- Which of the following alkali metal halides has the largest lat-tice energy? Explain. (a) (b) (c)
Problem 29
- The following diagram shows the potential energy of two atoms as a function of internuclear distance. Match the descriptions with the indicated letter on the plot. (a) Repulsive forces are high between the two atoms. (b) The two atoms neither exert attractive nor repulsive forces on one another. (c) The attractive forces between atoms are maximized, resulting in the lowest energy state. (d) Attractive forces between atoms are present but are not at maximum strength.
Problem 31
- The following diagram shows the potential energy of two atoms as a function of internuclear distance. Which bond is the strongest? Which bond is the longest?
Problem 32
Problem 33
Two electrostatic potential maps are shown, one of methyl-lithium (CH3Li) and the other of chloromethane (CH3Cl). Based on their polarity patterns, which do you think is which? (a)
(b)
Problem 34
Electrostatic potential maps of acetaldehyde (C2H4), ethane (C2H6), ethanol (C2H6O), and fluorethane (C2H5F) are shown. Which do you think is which? (a)
(b)
(c)
(d)
- Characterize bonds between the two atoms as covalent or ionic. (a) Cl and F (b) Rb and F (c) Na and S (d) N and S
Problem 35
- The following ball-and-stick molecular model is a representation of thalidomide, a drug that causes birth defects when taken by expectant mothers but is valuable for its use against leprosy. The lines indicate only the connections between atoms, not whether the bonds are single, double, or triple. (Red = O, gray = C, blue = N, ivory = H). Give the formula of thalidomide, and indicate the positions of multiple bonds and lone pairs.
Problem 37
- Match the following descriptions with the type of bond (ionic, nonpolar covalent, covalent). (a) One or more electrons are transferred from a metal to a nonmetal atom.
Problem 40
- Why do two atoms come together to form a covalent bond? (a) Attractive forces between the positively charged nuclei and the electrons in both atoms occur when the atoms are close together. (b) Repulsive forces between protons in the nuclei of the two atoms are minimized when the atoms are close together. (c) Repulsive forces between electrons in the two atoms are minimized when the atoms are close together.
Problem 41
- Explain the difference in the bond dissociation energies for the following bonds: (C-F, 450 kJ/mol), (N-F, 270 kJ/mol), (O-F, 180 kJ/mol), (F-F, 159 kJ/mol).
Problem 42
Problem 46
What general trends in electronegativity occur in the periodic table?
Problem 47
Predict the electronegativity of the undiscovered element with Z = 119.
- Order the following elements according to increasing electronegativity: Li, Br, Pb, K, Mg, C.
Problem 48
- Order the following elements according to decreasing electronegativity: C, Ca, Cs, Cl, Cu.
Problem 49
- Which of the following substances contain bonds that are largely ionic? (a) HF (b) HI (c) PdCl2 (d) BBr3 (e) NaOH (f) CH3Li
Problem 50
- Show the direction of polarity for each of the bonds in Problem 7.51 using the notation. (b) Si-Li or Si-Cl
Problem 52
- Which of the substances CdBr2, P4, BrF3, MgO, NF3, BaCl2, POCl3, and LiBr contain bonds that are: (b) nonpolar covalent?
Problem 54
- Which of the substances S8, CaCl2, SOCl2, NaF, CBr4, BrCl, LiF, and AsH3 contain bonds that are: (a) largely ionic? (b) nonpolar covalent? (c) polar covalent?
Problem 55
- Order the following compounds according to the increasing ionic character of their bonds: CCl4, BaCl2, TiCl3, ClO2.
Problem 56
- Using only the elements P, Br, and Mg, give formulas for the following. (b) A molecular compound with polar covalent bonds that obeys the octet rule and has no formal charges
Problem 58
Problem 58a
Using only the elements P, Br, and Mg, give formulas for the following. (a) An ionic compound