The chemical element with the atomic number 1 is hydrogen. It is the simplest and lightest element on the periodic table, consisting of just one proton and one electron. Hydrogen is abundant in the universe, constituting approximately 75% of its elemental mass. This element plays a crucial role in various chemical reactions, including forming water when it combines with oxygen. Additionally, hydrogen serves as a vital component in many energy-related technologies, such as fuel cells. Its versatility makes it essential for both industrial processes and scientific research, contributing to advancements in multiple fields.