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Essay Questions for Unit 8 & 9 Bonding

1. Answer the following questions using principles of chemical bonding and molecular geometry. Lewis electron – dot diagrams and sketches of molecules may be helpful as part of your explanations. For each answer you must include references to both substances.

i.Consider the carbon dioxide molecule, CO2, and the carbonate ion, CO32-

  1. Draw the complete Lewis electron dot structure for each species.
  2. Account for the fact that the carbon – oxygen bond length in CO32- is greater than the carbon – oxygen bond length in CO2

ii.Consider the molecules CF4 and SF4.

  1. Draw the complete Lewis electron dot structure for each species.
  2. In terms of molecular geometry, account for the fact that CF4 molecule is nonpolar, whereas the SF4 molecule is polar.

iii.The bonds in nitrite ion, NO21- are shorter than the bonds in nitrate ion, NO31-

iv.The CH2F2 molecule is polar, whereas the CF4 molecule is not.

v.The atoms in a C2H4 molecule are located in a single plane, whereas those in C2H6 molecule are not.

vi.The shape of a PF5 molecule differs from that of an IF5 molecule.

vii.Compounds containing Kr have been synthesized, but there are no known compounds that contain He.

viii.The shape of ICl41- ion is square planar, whereas the shape of the BF41- ion is tetrahedral.

ix.Draw the Lewis structure for CF4, PF5 and SF4.

  1. What is the bond F --- C --- F bond angle in CF4?
  2. What is the hybridization of the valence orbitals of P in PF5?
  3. What is the geometric shape formed by the atoms in SF4?

xii. GeCl4SeCl4ICl41-ICl41+

The species represented above all have the same number of chlorine atoms attached to the central atom.

  1. Draw the Lewis structures of each of the four species. Show all valence electrons in your structures.
  2. What is the Cl – Ge -- Cl bon angle in GeCl4?
  3. Is SeCl4 polar? Explain.
  4. What is the hybridization of the I atom in ICl41-?
  5. What is the geometric shaped formed by the atoms in ICl41+?

x.Boron commonly forms molecules of the type BX3. These molecules have a trigonal planar structure.

xi.Answer the following questions about the structures of ions that contain only sulfur and fluorine.

  1. The compounds SF4 and BF3, react to form an ionic compound according to the following equation.

SF4 + BF3 SF3BF4

  1. Draw a complete Lewis structure for the SF31+ cation in SF3BF4
  2. Identify the type of hybridization exhibited by sulfur in the SF31+ cation.
  3. Identify the geometry of the SF31+ cation that is consistent with the Lewis structure draw above.
  4. Predict whether the F – S – F bond angle in the SF31+ cation is larger than, equal to, or smaller that 109.5o. Justify your answer.
  1. The compounds SF4 and CsF react to form an ionic compound according to the following equation.

SF4 + CsF  CsSF5

  1. Draw a complete Lewis structure for the SF51- anion in CsSF5.
  2. Identify the type of hybridization exhibited by the sulfur in the SF51- anion.
  3. Identify the geometry of the SF51- anion that is consistent with the Lewis structure drawn above.
  4. Identify the oxidation number of sulfur in the compound CsSF5.