Hydrogen on the periodic table
Hydrogen (chemical symbol H and atomic number 1) is a chemical element. It is thought to be the most abundant element in the universe. It is also the lightest element on the periodic table.
Hydrogen is a gas at room temperature. Its melting and boiling points are very low (approximately 14 K and 20 K above absolute zero, respectively).
Water (H2O) is a well-known chemical compound, which consists of two hydrogen atoms and one oxygen atom.