Which is the most abundant element in the universe?

The story behind the answer

Hydrogen is the most abundant element in the universe because it was produced in vast quantities during the first few minutes after the Big Bang. As the simplest atom—one proton and one electron—it formed easily when the universe cooled, making up about 75% of its elemental mass (and over 90% of its atoms). Stars are largely hydrogen, and they shine by fusing hydrogen into helium.

For context, helium is the second most abundant, while elements like oxygen and lithium are far less common on a cosmic scale (oxygen is abundant on Earth but not universe-wide). Memory tip: Hydrogen is element number 1 on the periodic table—and it’s also number 1 in the universe.