The chemical symbol for hydrogen is **H**. It is the first element on the periodic table and has an atomic number of 1. As the simplest and most abundant element in the universe, hydrogen plays a crucial role in the formation of stars and the composition of molecules, including water (H2O) and organic compounds. Hydrogen exists primarily as diatomic molecules (H2) under standard conditions. It is used in various industrial applications, including the production of ammonia for fertilizers, refining petroleum, and as a potential clean fuel source. Its properties make hydrogen a focus of research in energy and environmental sciences.