Explain how hydrogen and helium nuclei were first formed in the universe.

The low mass, elements hydrogen, and helium were produced in the hot, dense conditions of the birth of universe itself. The birth, life, and death of a star are described in terms of nuclear reactions. The chemical elements that make up the matter we observe throughout the universe were created in these reactions.

Hydrogen and helium nuclei were formed in the universe through a process called nucleosynthesis. deuterium (a hydrogen isoptope) nuclei were formed when protons and neutrons combined. neutrons combined with deuterium nuclei to form tritium. a proton would then fuse with tritium to form helium nuclei.