EVERYDAY SCIENCE

Detailed explanation-1: -After the universe cooled slightly, the neutrons fused with protons to make nuclei of deuterium, an isotope of hydrogen. Deuterium nuclei then combined to make helium. Further reactions between protons, neutrons, and different isotopes of helium produced lithium.

Detailed explanation-2: -Within about 3 minutes after the Big Bang, conditions cooled enough for these protons and neutrons to form hydrogen nuclei. This is called the era of nucleosynthesis. Some of these nuclei combined to form helium as well, though in much smaller quantities (just a few percent).

Detailed explanation-3: -It took 380, 000 years for electrons to be trapped in orbits around nuclei, forming the first atoms. These were mainly helium and hydrogen, which are still by far the most abundant elements in the universe.

Detailed explanation-4: -Most of the hydrogen and helium in the Universe were created in the moments after the Big Bang. Heavier elements came later.

Detailed explanation-5: -Hydrogen and helium atoms emerged a measly 379, 000 years after the Big Bang. As the hot, dense plasma of protons, electrons and photons that was the universe began to cool and expand, electrons and protons gathered to form atoms.