Bonding Review
1. How many valence electrons in each of the following atoms?
a) Br b) C c) Na d) Se e) S-2 f) Na+1
2. Write the electron dot diagram for each of the elements in question 1.
3. Using the electron dot diagrams for sodium and oxygen, show how sodium oxide
will form.
4. How many electrons do each of the following gain or lose to form an ion?
a) Br b) I c) Ca d) Se
5. Why do the elements listed in question 4 want to gain or lose electrons?
6. Write the formula for the ionic compound that forms when each pair of elements
combine.
a) magnesium and bromine b) aluminum and sulfur c) lithium and phosphorus
7. Name the compounds in question 6.
8. Explain the difference between an ionic bond and a covalent bond.
9. Explain the difference between a polar and nonpolar bond. What type of bonds
are these, ionic or covalent?
10. Draw electron dot structures (Lewis dot diagrams) for the following compounds.
a) CHCl3 b) NH3 c) O3 d) PO4-3 e) HCN f) XeF4 g) PCl5 h) SO3 i) NO
j) SF6
11. Identify the shape for all the molecules in question 10, except f).
12. State whether each molecule will be polar or nonpolar in question 10.
13. Which is harder to break, a single bond or a double bond?
14. Draw the resonance structures for SO3.
15. What is the VSEPR theory and how does it predict the shape of a molecule?
16. List the following pairs in order from least ionic character to most ionic character.
a) O - F b) Cl - O c) K- O d) Li - N
17. State whether each of the following compounds are ionic or covalently bonded.
a) NaCl b) CH4 c) K2O d) Li3N e) H2O
18. Explain how Na3PO4 has more than one type of bonding in it.
19. What is hydrogen bonding?
20. Explain how HCl can become a liquid (explain the intermolecular forces).
21. Explain how I2 can be a solid when it does not have a dipole to attract another
molecule.
22. Why will CaCl2 dissolve in water?
23. Will CH3OH dissolve in water? Why or why not?
24. Will C8H18 dissolve in water? Explain.
25. If either 23 or 24 did not dissolve in water, what might be an alternative? Why?
26. Draw the electron dot diagram and show the partial charges for the following:
a) HCl b) H2S c) CCl4
27. CCl4 has polar bonds in it. Why is the molecule nonpolar?
28. A given substance is a white solid at 25 °C. It melts at 450 °C and will conduct an
electric current when molten. What type of a substance might this be?
29. A white solid melts at 1500 °C and will not conduct electricity, even when
molten. Classify the substance as best you can from these properties.
30. Compare the bond angles in CH4, NH3, and H2O. Explain the differences.
31. List C2H6, C2H2, and C2H4 in order of shortest C - C bond to longest. Give your
reasoning.
32. Knowing the following bond energies in kJ mol-1: C-H = 413, C-Cl = 339, find
the energy required to make CHCl3 from its atoms.
33. Knowing the following bond energies in kJ mol-1: C-H = 413, Cl-Cl = 239, F-F=
154, C-F = 485, C-Cl = 339, H-F = 565, and H-Cl = 427, find the enthalpy of the
reaction:
CH4 (g) + 2 Cl2 (g) + 2 F2 (g) --> CF2Cl2 (g) + 2 HF (g) + 2 HCl (g)
Bonding Review
1. a) 7 b) 4 c) 1 d) 6 e) 8 f) 8
2.
3.
4.
5.
6.
7.
8.
9.
a) gain 1 b) gain 1 c) lose 2 d) gain 2
To obtain a full outer shell and become like an inert gas.
a) MgBr2 b) Al2S3 c) Li3P
a) magnesium bromide b) aluminum sulfide c) lithium phosphide
Ionic - complete transfer of electrons, covalent - sharing of electrons
Polar - net partial charge, difference in electronegativity between the two
elements. Nonpolar - very small difference in electronegativity, no partial
charges. Both are covalent bonds.
10.
11. a) tetrahedral b) pyramidal c) bent d) tetrahedral e) linear f) (square planar)
g) trigonal bipyramidal h) trigonal planar i) linear j) octahedron
12. a,b,e,i - polar the rest - nonpolar
13. double - shorter bond length, more electrons shared
14.
15. Valence Shell Electron Pair Repulsion theory - all atoms (shared pairs) and
unshared electrons want to spread out as much as possible.
16. (O - F, Cl - O), Li - N, K - O
17. a) ionic b) covalent c) ionic d) ionic e) covalent
18. It is ionic between the Na+ and the PO4-3 ions. Covalent within the PO4-3 ion.
19. Stronger dipole interactions which occur between molecules when H is bonded to
either F, N, or O. This occurs because H is very electron deficient, having more of
a partial positive charge than usual. The others have more of a partial negative
charge.
20. HCl is a dipole and the + on the H is attracted to Cl (with a -) on a separate
molecule. This attraction holds the molecules closer together to allow the
substance to become a liquid.
21. Dispersion forces or Induced dipoles. Dispersion forces are thought to be do to the
motion of electrons. The more electrons present, the stronger the dispersion
forces. Induced dipoles may also play a factor. An instantaneous dipole may form
on one I2 molecule which can induce a dipole in another and have an
instantaneous, weak attraction.
22. It is ionic and the + and - ions are attracted to the + and - on the water molecule.
23. Yes. It is polar and will have dipole interactions with water to allow it to dissolve.
24. No. It is nonpolar and will not be attracted to water. (Small amounts of nonpolar
substances may dissolve due to induced dipoles, but not much.)
25. For 24, use oil or another nonpolar liquid.
26.
27. The polar bonds pull evenly on the central atom, giving no net result.
28. metallic
29. network solid
30. CH4 has the largest bond angles because all the electron pairs are shared. NH3 is
smaller because the unshared pair of electrons repel the shared pairs (hydrogen
atoms) more than a shared pair, pushing the hydrogens closer together. H2O has
the smallest bond angle because it has two unshared pairs of electrons which repel
each other even more, pushing the hydrogens even closer together.
31. C2H2, C2H4, C2H6. Triple bonds are the shortest, single bonds the longest.
32. Forming 3 C-Cl bonds, 1 C-H bond. Enthalpy = 3(339) + 1(413) = 1430 kJ.
33. CH4 (g) + 2 Cl2 (g) + 2 F2 (g) --> CF2Cl2 (g) + 2 HF (g) + 2 HCl (g)
Hrxn = Energy needed to break bonds - Energy needed to form bonds.
Bonds to break: 4(C-H), 2(Cl-Cl), 2(F-F)
Bonds to form: 2(C-F), 2(C-Cl), 2(H-F), 2(H-Cl)
Hrxn = [4(413) + 2(239) + 2(154)] - [2(485) + 2(339) + 2(565) + 2(427)] = -1194
kJ