Final answer:
Hydrogen (H) is the lightest and most abundant element, serving as the fuel for stars and found extensively in compounds like water and organic substances.
Step-by-step explanation:
The lightest and most abundant element in the universe, essential as fuel for the Sun and other stars, and found in countless compounds including water and most carbon-containing substances, is Hydrogen (H). Hydrogen's light atomic mass contributes to its abundance and reactivity, resulting in it being trapped in compounds such as water (H₂O), hydrocarbons, and organic matter. In the cosmos, hydrogen makes up about 90% of atoms, serving as the primary element in stars, where it undergoes fusion to produce energy and create heavier elements.
A Closer Look at Hydrogen
On Earth, hydrogen is generally found bonded with oxygen in the form of water, covering about 70% of the planet's surface. Hydrogen comprises only .9% of the Earth's mass and 15% of its volume, with a minuscule presence in the atmosphere due to its extreme flammability and lightness, which allows it to escape into space more readily than heavier gases. Not only is hydrogen essential in the composition of water, but it is fundamentally part of life's chemistry along with carbon, nitrogen, and oxygen.