Hydrogen is the most abundant element in the Universe. According to the Big Bang Theory, the Universe at the beginning expanded and later cooled to form subatomic particles and the simplest elements. Hydrogen along with some helium and lithium is the first element that came into existence in the Universe. Hydrogen is the most abundant element in the Universe; it accounts for almost 73 to 75% of all matter in the Universe.
Helium is the second most abundant element which is approximately 24%. Both represent 99% of the total matter. Oxygen follows helium as the third most abundant element. Then there are traces of other elements like carbon, nitrogen, iron, and many others.