which like O 2 is paramag-netic). Because the S 8 molecule is nonpolar, it is soluble in liquids such as CS 2 and C 6 H 6.Selenium also consists of cyclic molecules that contain eight atoms, and tellurium is essentially metallic in char-acter. In their vapors, several species are found that contain 2, 6, or 8 atoms. Both are useful as semi-conductors, and selenium has been used in rectifiers. Because the electrical conductivity of selenium increases as the intensity of illumination increases, it has been used to operate electrical switches that open or close as a light beam is broken. Selenium was also used in light meters, but other types of meters are now available that are more sensitive. Table 15.1gives a summary of the properties of the group VIA elements.