According to the Brönsted-Lowry concept, a conjugate acid is formed when a base accepts a proton ($\text{H}^+$) . The given species is the amide ion ($\text{NH}_2^-$), which acts as a base. When $\text{NH}_2^-$ accepts a proton, it forms ammonia ($\text{NH}_3$): $\text{NH}_2^- + \text{H}^+ \rightarrow \text{NH}_3$ Therefore, the conjugate acid of $\text{NH}_2^-$ is $\text{NH}_3$ .