What is the most abundant element in the universe?

Hydrogen is the most abundant element in the universe, making up about 74% of its elemental mass. This is primarily because hydrogen was the first element formed during the Big Bang, leading to its dominance in the cosmos. It serves as the building block for all other elements: through the process of nuclear fusion in stars, hydrogen atoms combine to form helium and other heavier elements.

The significant proportion of hydrogen is crucial in the lifecycle of stars, driving the processes that create heavier elements. In contrast, helium, while the second most abundant element, constitutes about 24% of the universe's mass, followed by lithium and carbon, which are much less abundant. This hierarchical representation of elemental abundance highlights hydrogen’s foundational role in the universe's composition and the formation of matter.