What is the most abundant element in the universe?

Hydrogen is recognized as the most abundant element in the universe, making up about 75% of its elemental mass. It is the simplest and lightest element, consisting of just one proton and one electron. This elemental dominance arises from the conditions present during the formation of the universe, particularly during the Big Bang, when hydrogen was produced in vast amounts.

In addition to its abundance, hydrogen is a crucial building block for the universe's structure and is fundamental in nuclear fusion processes that power stars, including our Sun. Stars primarily fuse hydrogen into helium through nuclear reactions, a process that not only generates energy but also leads to the synthesis of heavier elements over time. This fundamental role in star formation and evolution underscores hydrogen's importance in cosmology and astrophysics.

While elements like helium, oxygen, and carbon are certainly significant in various astronomical and biological contexts, none come close to matching hydrogen’s dominance in the cosmic landscape. Helium is the second most abundant element but makes up only about 25% of the elemental mass, while carbon and oxygen are much less prevalent in comparison, primarily found in specific contexts such as within stars and planets.