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    Chemical Element
    Hydrogen is a chemical element with chemical symbol H and atomic number 1. With an atomic weight of 1.00794 u, hydrogen is the lightest element on the periodic table. Wikipedia 

    Symbol: H
    Atomic mass: 1.00794 u ± 0.00001 u
    Melting point: -434.5°F (-259.2°C)

What makes a hydrogen car possible is a device called a fuel cell, which converts hydrogen to electricity, giving off only heat and water as byproducts.