The second lightest element on the periodic table is helium. Helium has an atomic number of 2, which means it has two protons in its nucleus. It is the second element in the periodic table and is represented by the symbol "He." Helium is a noble gas and is the second most abundant element in the universe, after hydrogen. It is a colorless, odorless, and non-toxic gas that has various applications, including filling balloons, cooling scientific instruments, and as a protective gas in welding.