Download Lewis Structures & Bond Properties: H2, Cl2, H2O, H3CCH3, H2CCH2, HCCH, CO2, H2CO, N2, O2 and more Exams Chemistry in PDF only on Docsity!
Drawing Lewis Structures and
Correlating with Bond Orders, Bond Lengths, and Bond Energies
Draw the Lewis structure for each compound in the table and then answer the questions on the reverse side of this sheet. Molecule Lewis Structure Bond of Interest Bond Order Bond Length (nm) Bond Energy (kJ/mol) H 2 H–H 1 0.074 436 Cl 2 Cl–Cl 1 0.198 243 H 2 O (^) O–H 1 0.103 464 H 3 CCH 3 C–C 1 0.154 346 H 2 CCH 2 C–C 2 0.133 615 HCCH C–C 3 0.120 835 CO 2 C–O 2 0.120 804 H 2 CO (^) C–O 2 0.120 799 N 2 N–N 3 0.116 945 O 2 O–O 2 0.121 498
The bond order between two atoms is equal to the number of shared pairs of electrons mak- ing up the particular bond. In a single bond, for example, a single pair of electrons is shared, giving a bond order of one. When two electron pairs are shared we have a double bond, or a bond order of two. A triple bond, of course, involves the sharing of three pairs of electrons and a bond order of three. What is the bond order for the bond of interest in the com- pounds for which you drew Lewis structures? Answers shown on reverse side of this page. What correlation, if any, do you find between bond order and bond strength. Briefly summa- rize your reasoning. As bond order increases, the strength of the bond increases as well. The compounds H 3 CCH 3 , H 2 CCH 2 , and HCCH show this trend nicely. The bond energy for Cl 2 is shown on the other side of this page. The bond energy for the Br–Br bond in Br 2 is 224 kJ/mol and that for the I–I bond in I 2 is 151 kJ/mol. What corre- lation, if any, does this suggest between bond length and bond strength. Briefly summarize your reasoning. As bond length increases the bond becomes weaker; we know that the bond length in I 2 is greater than that in Br 2 , which is greater than that in Cl 2 and we see that the weakest of the bonds is for I 2 and the strongest is for Cl 2_._ Which do you think is more important when it comes to predicting a bond’s energy: bond order or bond length? Briefly explain. The more important predictor of bond strength is bond order. The two compounds with triple bonds have stronger bonds than the four compounds with double bonds, which, in turn, have stronger bonds than the four compounds with single bonds. Draw a Lewis structure for methanol, H 3 COH, and predict whether it will take more energy to break the C–O bond in methanol or that in formaldehyde, H 2 CO (see table on other side). Methanol has a single bond between C and O while formaldehyde as a double bond between C and O. Given the importance of bond order, we predict it will be easier to break the C–O bond in methanol.
