Which element has one electron in its fourth and outermost main energy level

oxygen, selenium, tellurium, and polonium.

they're all from the same group as sulfur (group 16).

each chemical family is represented as a group or column on the periodic table. based on chemical properties, there are 6 types of chemical families. group 1 represents alkali metals, group 2 represents alkaline earth metals, groups 3 to 12 represent transition metals, groups 13 to 16 represent non-metals and other metals, group 17 represents halogens and group 18 represents noble gases.