What element has the atomic number 1?

The element that holds the distinction of having an atomic number of 1 is hydrogen. This fundamental characteristic stems from the definition of an atomic number itself, which is determined by the number of protons found in the nucleus of an atom. In the case of hydrogen, its atom contains a single proton, making it the simplest and lightest of all elements. This singular proton dictates its position at the very beginning of the periodic table.

Beyond its atomic structure, hydrogen is remarkably significant throughout the universe. It is the most abundant element, comprising approximately 75% of all normal matter by mass and about 90% of all atoms. This includes its role as the primary fuel for stars, like our sun, where hydrogen atoms undergo nuclear fusion to release immense amounts of energy, allowing stars to shine for billions of years.

On Earth, hydrogen rarely exists in its pure elemental form due to its lightness, often bonding with other elements. It is famously a component of water (H2O) and is crucial in all organic compounds, making it essential for life. As a colorless, odorless, and tasteless gas, hydrogen has also garnered attention as a promising clean energy carrier, with its potential use in fuel cells to produce electricity with only water vapor as a byproduct. The element was first recognized as a distinct substance by Henry Cavendish in 1766 and later named by Antoine Lavoisier, derived from Greek words meaning "water-former."