Hydrogen
. Hydrogen, chemical element that exists as a gas at room temperature. Hydrogen gas is odorless, tasteless, colorless, and highly flammable. When hydrogen gas burns in air, it forms water. French chemist Antoine Lavoisier named hydrogen from the Greek words for “water former.” Hydrogen has the smallest atoms of any element. (Atoms are the smallest particles that have the characteristics of a chemical element.) A hydrogen atom contains one proton , a tiny particle with a positive electrical charge, and only one electron , an even smaller, negatively charged particle. The proton is the center, or nucleus , of the hydrogen atom, and the electron travels around the nucleus. Pure hydrogen exists as hydrogen gas, in which pairs of hydrogen atoms bond together to make larger particles called molecules . See also Atom . Hydrogen is the first element in the periodic table of the elements and is represented by the symbol H (see Periodic Law ). The periodic table lists elements by their atomic nu