Question: neutrons that combined with protons in an atomic nucleus early in the universe's history form
Answer: In physical cosmology , Big Bang nucleosynthesis ( abbreviated BBN , also known as primordial nucleosynthesis , arch ( a ) eonucleosynthesis , archonucleosynthesis , protonucleosynthesis and pal ( a ) eonucleosynthesis ) refers to the production of nuclei other than those of the lightest isotope of hydrogen ( hydrogen - 1 , H , having a single proton as a nucleus ) during the early phases of the Universe .