What is hydrogen
Hydrogen is the element with atomic number 1; it consists of one proton and one electron (1s1) and is the smallest and lightest among elements. It forms a diatomic molecule H2, which is colorless, odorless and flammable gas. Hydrogen gas is about 14.5 times less dense than the air. Hydrogen is the most abundant element in the Universe, and one of the most abundant elements on Earth and in living organisms.