Which element has the atomic number 1?

The element with the atomic number 1 is hydrogen. The atomic number of an element refers to the number of protons found in the nucleus of an atom of that element. Since hydrogen has one proton, its atomic number is designated as 1. This fundamental characteristic of hydrogen makes it the simplest and lightest element on the periodic table. It's essential in various chemical reactions and is a primary component of water and organic compounds, playing a critical role in both chemistry and biology. The other elements listed—oxygen, carbon, and helium—have higher atomic numbers, indicating that they possess more protons in their nuclei than hydrogen.