Which element has the atomic number 1?

Hydrogen is the element with atomic number 1, which means it is the simplest and lightest element in the periodic table. It consists of only one proton in its nucleus, which defines its identity as hydrogen. This unique characteristic places it at the beginning of the periodic table and makes it fundamental to the structure of all matter in the universe.

In the context of the other elements listed, oxygen, carbon, and nitrogen have higher atomic numbers. Oxygen has an atomic number of 8, carbon is 6, and nitrogen is 7, which indicates that they each have more protons in their nuclei compared to hydrogen. Thus, the distinction of hydrogen as the first element not only establishes its place in the periodic table but also underscores its importance in chemistry, including its role in forming water and organic compounds.