Brief Description:
Hydrogen is the lightest and most abundant element in the universe; it is estimated that hydrogen makes up over 90% of all matter. Stars use hydrogen as fuel, fusing it into helium and releasing tremendous amounts of energy. Hydrogen is highly flammable in air, forming H₂O when combusted with oxygen. Its low density makes it an excellent lifting agent, but its explosivity also makes it dangerous. Sources: Decomposition of water, acid-metal reactions.