Electrostatic potential diagram

FIGURE 6.34 An electrostatic potential diagram of ethanol, C2H OH. An electronegative atom (here, the O atom) can pull electrons toward itself from more distant parts of the molecule, as shown by the red tint over the O atom. Hence it can influence the strengths of bonds even between atoms to which it is not directly attached. 

For polyatomic molecules, it is important to distinguish between a polar molecule and a polar bond. Although each bond in a polyatomic molecule may be polar, the molecule as a whole will be nonpolar if the dipoles of the individual bonds cancel one another. For example, the two 8+C—O8- dipoles in carbon dioxide, a linear molecule, point in opposite directions, so they cancel each other (30). As a result, C02 is a nonpolar molecule even though its bonds are polar. The electrostatic potential diagram (31) illustrates this conclusion. In contrast, the two 8-0—H8+ dipoles in H20 lie at 104.5° to each other and do not cancel, so H20 is a polar molecule (32). This polarity is part of the reason why water is such a good solvent for ionic compounds. 

Another way to represent the charge distribution in HF is by an electrostatic potential diagram (see Fig. 8.4). For this representation the colors of visible light are used to show the variation in charge distribution. Red indicates the most electron-rich region of the molecule and blue indicates the most electron-poor region. 

Figure 8.6 (a) The structure and charge distribution of the ammonia molecule. The polarity of the N—H bonds occurs because nitrogen has a greater electronegativity than hydrogen, (b) The dipole moment of the ammonia molecule oriented In an electric field, (c) The electrostatic potential diagram for ammonia. 

IS. The following electrostatic potential diagrams represent H2, HCl, or NaCl. Label each and explain your choices. 

Given the following electrostatic potential diagrams, comment on the expected solubility of CH4 in water and NH3 in water. 

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