The most abundant element in the universe is hydrogen. Approximately 75 percent of all matter is composed of hydrogen. As of 2015, 90 percent of the visible universe is comprised of hydrogen.
Hydrogen is the simplest element in the universe, consisting of only one proton and one electron. It was first classified as an element in 1766 by Henry Cavendish and is the first element on the periodic table with an atomic number of 1. Hydrogen has an extremely low melting and boiling point at minus 434.81 degrees Fahrenheit and minus 423.17 degrees Fahrenheit respectively. At room temperature, hydrogen is a gas.