Welcome to Authorea!

    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.
where will we get the hydrogen?
How expensive will these fuel-efficient cars be to purchase?
Will you be able to find a hydrogen fuelling station to refill your tank?
And, perhaps most importantly, as a fuel, is hydrogen really as non-polluting as it seems?

In 1839, the Welsh scientist Sir William Robert Grove took the familiar electrochemical process of electrolysis, which uses electricity to produce hydrogen from water, and reversed it, generating electricity and water from hydrogen. He called his invention a gas voltaic battery.