Hydrogen - the universe's most common element
Hydrogen (chemical symbol H, Latin Hydrogenium) is the lightest and simplest gaseous chemical element, forming the bulk of matter in the universe. It has a wide practical use as an energy source, reducing agent in chemical synthesis or metallurgy, as well as filling for meteorological and fairground balloons and, until the 1930s, airships.
Hydrogen is a colorless, light gas, tasteless and odorless. It is flammable, burns with a bluish flame, but does not support burning. It is 14.38 times lighter than air and conducts heat seven times better than air. Hydrogen is stable at normal temperatures. It is considerably more reactive when heated, especially with oxygen, and halogens combine very violently, although initialization is required to trigger this reaction (e.g., a spark that ignites an oxy-hydrogen flame). Hydrogen is very slightly soluble in water, but some metals absorb it (preferably palladium).
Hydrogen forms compounds with all the elements of the periodic table (with the exception of rare gases), especially carbon, oxygen, sulfur and nitrogen, which form the basic building blocks of life on Earth.
Hydrogen is able to form a special type of chemical bond, called a hydrogen bond or also a hydrogen bridge, where the bound hydrogen atom has an affinity for other atoms with which it is not bound by a classical chemical bond. The hydrogen bond with oxygen atoms is extremely strong, which explains the anomalous physical properties of water (high boiling and melting points, etc.).