The Universe's Foundation Element
Hydrogen stands as the simplest and most abundant element in the universe, comprising approximately 75% of all normal matter. With just one proton and one electron, it serves as the fundamental building block from which all other elements are forged in the hearts of stars.
Physical Properties
At standard conditions, Hydrogen exists as a colorless, odorless, tasteless diatomic gas (H₂). It's the lightest element with a density 14 times less than air, causing Hydrogen-filled balloons to rise rapidly. The element becomes liquid at an extremely cold -253°C (-423°F) and solid at -259°C (-434°F).
Chemical Characteristics
Hydrogen exhibits unique chemical behavior, acting as both a reducing agent and oxidizing agent depending on reaction conditions. It readily forms covalent bonds with nonmetals and ionic compounds with active metals. The H-H bond energy of 436 kJ/mol makes H₂ relatively stable, requiring activation energy for most reactions.
Isotopic Varieties
Protium (¹H): 99.985% abundance - the "normal" Hydrogen with no neutrons
Deuterium (²H or D): 0.015% abundance - "heavy Hydrogen" with one neutron, used in nuclear fusion
Tritium (³H or T): Trace amounts - radioactive with two neutrons, half-life of 12.3 years