Rosa Vila Carbon Atom Necklace for Science and Chemistry Lovers and Enthusiasts - Basis of Life Dimension: 1.5" x 1.5" x 17" Unique Carbon Atom Inspired Necklace - Great for everyday wear or or special occasions. Carbon atom - a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen. Carbon is essential to all known living systems, and without it life as we know it could not exist