Hydrogen


 * Liquid hydrogen has the lowest density of any liquid.
 * Solid, crystalline hydrogen has the lowest density of any crystalline solid.
 * Hydrogen is the only element that can exist without neutrons. Hydrogen's most abundant isotope has no neurons.
 * Antihydrogen is the only antimatter element made so far, with atoms of antihydrogen synthesized at CERN lasting for as long as 1000 seconds. Each atom of antihydrogen contains a positron (positively charged version of the electron) orbiting an antiproton (negatively charged version of the proton).