ADAM HART-DAVIS / SCIENCE PHOTO LIBRARY ADAM HART-DAVIS / SCIENCE PHOTO LIBRARY
Molecular models of assorted chlorofluorocarbons (CFCs), showing the positions of the carbon (black), hydrogen (white), chlorine (dark green) & fluorine (red) atoms. The three smaller molecules all have an extra chlorine atom hidden from view behind the central carbon atom. At upper left is trichlorofluoromethane (CFCl3), used for blowing foams, & at lower left is dichlorodifluoromethane (CF2Cl2), which is used in refrigeration. At lower right is trichloromethane (chloroform, CHCl3) & at upper right is tetrachlorofluoro- ethane. Atmospheric pollution by CFCs is thought to be responsible for the annual appearance of a hole in the ozone layer over Antartica.
Model release not required. Property release not required.