In some molecules, there is a more negative charge on one side of the molecule and a more positive charge on the other.  Hydrogen bromide is an example of a molecule in which there is such a charge distribution.  

     In order to visualize the electrostatic potential for this molecule, do the following:

  1.  Use the mouse to position the molecule in a left-right orientation. With your cursor on the model, use the right mouse button to open the Chime menu. (One a Mac, Click the mouse on the molecule and hold the click.) 

  2.  Go to Select, then to Display List, and finally to Create Molecular Surface.  

  3. Click again on the molecule and choose Select, Display List, Color, Electrostatic Potential and finally Color Red-White-Blue.  In this color scheme, the blue represents positive and the red negative.