The element hydrogen is extremely flammable and is often described as the most flammable of all known substances. Hydrogen can be ignited by heat, sunlight or a small spark. When pure hydrogen burns, ultraviolet light rays are emitted, making the flames difficult to view with the naked eye.
Hydrogen is the most abundantly available element in the universe. The chemical symbol of hydrogen is H, and its atomic number is one. The atomic weight is 1 as well, which makes it the lightest of all elements. Hydrogen is a colorless gas and appears in the first position on the periodic table.