This element attacks a carbon singly-bonded to this element in the first step of native chemical ligation. This element is the central nonmetal in a compound that reacts with oxalyl chloride in the beginning (10[1])of the Swern oxidation. This element substituted with two methyl groups is doubly-bonded to an oxygen (10[1])in a common organic solvent. (10[2])Clusters of iron (10[1])and this element are widely (10[1])present in enzymes that mediate biochemical electron (-5[1])transfers. (10[1])Cross-links with this element are created in vulcanization. This element bonded (10[1])to itself creates a namesake “bridge,” and this element bonded to hydrogen forms a thiol group, such as that in cysteine. For 10 points, name this chalcogen found under oxygen in the periodic table, which has a characteristic odor of rotten eggs. ■END■ (10[1])