We present first-principles molecular dynamics simulations of the formation of monatomic gold nanowires with different impurities (H, C, O, S). Special care was taken not to bias the probability that the impurity atoms participate in the monatomic wire, which is the main focus of this work. Hydrogen always evaporated before the formation of the monatomic chains. Carbon and oxygen were found in the final chains with low probability ( approximately 10%), while sulfur almost always participated in it (probabability approximately 90%). The mean distances between gold atoms bridged by carbon, oxygen, and sulfur were 3.3, 4.4, and 5.0 A, respectively, in good agreement with experimental observations. The contributions of carbon, oxygen, and sulfur to the density of electronic states at the Fermi level are neglegible, moderate, and large, respectively.