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. (10[1])This element (-5[1])substituted with two methyl groups is doubly-bonded to an oxygen (10[1])in a common organic solvent. (10[3])Clusters (10[1])of iron (10[3]-5[1])and this element are widely (10[1])present (10[2])in enzymes (10[1])that mediate (10[2])biochemical electron (-5[1])transfers. (10[2])Cross-links with this element (10[1])are created in vulcanization. (10[6])This element (10[1])bonded (10[2])to (10[1])itself (10[1])creates (10[1])a namesake “bridge,” (10[1])and this element bonded (10[2])to hydrogen (10[1])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[4])