Final answer:
The first element formed in the universe was hydrogen, followed closely by helium and a small amount of lithium. These light elements were produced through fusion immediately post-Big Bang, while heavier elements were created later in the cores of stars.
Step-by-step explanation:
The First Element in the Universe
The discussions of the early universe and the evolution of stars center around nucleosynthesis, or the process by which the nuclei of elements are built. According to our best models of the universe's formation, particularly during the first few minutes post-Big Bang, two of the simplest elements, hydrogen and helium, were formed, with a tiny amount of lithium as well.
Hydrogen was truly the first element to appear in the universe. Immediate after the Big Bang, when the universe was still extremely hot, fusion occurred producing hydrogen and helium in the most significant amounts. It wasn't until much later inside stars that the heavier elements were created. This information tells us that the universe started simple and grew in complexity as stars formed heavier elements through stellar nucleosynthesis.
Helium too plays a critical role as the second-most common element in the universe. However, despite this abundance, heavier elements like carbon, oxygen, and even uranium did not form until much later inside the cores of stars through fusion processes. Gamow and other scientists contributed to understanding this key aspect of how elements are formed in the universe.