How does the Big Bang theory explain why there is a lot of hydrogen and helium in the universe?

when the explosion happened the matter fussed into elements as the electrons portions Nd notrons were compresed into the elements beacuase hydrogen has 1 nutron proton and electron surronding its core

water at room temperature is flowing through a pipe with pressure taps located 10 ft apart along one section of the pipe, which are connected to a mercury (s=13.6) manometer.