Which is the most active nonmetallic element in group 16?

Oxygen

For metals, reactivity increases as we move through the elements in the period table from top to bottom, and left to right. In contrast, for nonmetals, reactivity increases as we move through the elements in the periodic table, as we move from bottom to the top, and right to left.

Group 16 on the periodic table is also called the oxygen family or chalcogens. It includes the following elements from top to bottom: Oxygen, Sulfur, Selenium, Tellurium, and Polonium. Of these, only Oxygen, Sulfur, and Selenium are nonmetals. Since reactivity of nonmetals increases going up the periodic table, oxygen is therefore the most reactive nonmetal in the group. Shown in the figure below is the reactivity trend in the periodic table.