Hydrogen: Chemical Element and Properties

Hydrogen Facts

• Hydrogen is the most abundant chemical substance in the universe.

Physical Properties of Hydrogen

• At standard conditions, hydrogen is in a gaseous state.

Atomic Structure of Hydrogen

• The most common isotope of hydrogen (symbol 1H) has:
  • 1 proton
  • 1 electron
  • 0 neutrons

Metallic Hydrogen

• Hydrogen becomes metallic under extremely high pressures, typically above 100 GPa.

Acid-Base Reactions

• Hydrogen plays a crucial role in acid-base reactions.

Combustion Properties of Hydrogen

• The enthalpy of combustion for hydrogen gas is -286 kJ/mol.
• The autoignition temperature of hydrogen gas in air is 500°C.

Ionic Compounds

• The symbol H+ represents a hydrogen ion in ionic compounds.

Hydrogen Flames

• Pure hydrogen-oxygen flames emit ultraviolet light, making them invisible.

History of Hydrogen Production

• Hydrogen gas was first artificially produced in the early 16th century through the reaction of acids with metals.