Carbon, we hardly know ye

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You are mostly water and carbon. Oh, sure, there is some nitrogen, oxygen and hydrogen, along with a host of other elements thrown in there, but you’re pretty much all carbon. You’re not alone either. From the biggest tree to the smallest virus, every living thing on this planet is carbon. In fact, carbon is so important to life that the branch of chemistry devoted to the study of carbon is called “organic chemistry.”

You may be asking yourself, “What is so special about carbon?” Well, the truth is, it is a pretty special atom. Unlike some of its atomic buddies, such as the alkali metals, carbon is extremely stable and doesn’t like to react too much — although it does like to react, unlike those snooty inert gasses such as neon and krypton. In fact, you could say that it has just the right amount of reactivity to be useful.

Carbon also has four available bonding sites, which again, isn’t too few to be useful, but isn’t too much to be unstable. Think of carbon’s bonding sites like you would parking spots around a building, with each one representing a place to park another atom. Because carbon is so stable, a wide variety of atoms can bond to it safely.

The fact that is has four sites is also significant; this allows carbon to form geometrically stable shapes, such as those found in graphite, diamond and even in your own DNA.

Despite this importance to life here on earth, extra terrestrial speculators or people who ponder the existence of interstellar life have often thought that, while it works pretty good down here on Earth, carbon might not be the only element capable of supporting life.

Silicon, which sits just below carbon on the periodic table, and shares many of carbon’s properties, has been suggested as an alternative to carbon since the late 1800s. However, biochemically-speaking, silicon does have some issues which call its usefulness into question.
When carbon is oxidized, like in cellular respiration — the process through which carbon-based life burns sugar to produce energy — carbon dioxide (CO2) is formed. Because it is a gas, the CO2 escapes our bodies through our lungs. When silicon is oxidized, which it does far more readily than carbon, silicon dioxide (SiO2) is formed. The sand enthusiasts among you will have correctly identified SiO2 as the basic building block in glass, which is not a gas — not even a little bit.

Furthermore, silicon’s extreme preference for oxygen makes the formation of anything other than oxygen containing compounds difficult at best, and unlikely at worst, severely limiting the versatility of silicon.

Finally, it is because of carbon that we know when the dinosaurs existed, and can form strong arguments to thwart the creationists. Most carbon here on earth exists in the form of carbon 12 (C-12), however a very specific percentage of the carbon in all living things is composed of the isotope carbon 14 (C-14), which has a slightly different and slightly less stable structure. Because C-14 decays into nitrogen at a predictable rate, and living things stop accumulating C-14 when they die, we can figure out when something, like a tyrannosaurus rex, died by measuring the C-12 to C-14 ratio in its remains. This is also known as radio-carbon-dating.

In conclusion, I would like to thank carbon. Unlike sodium, you don’t explode when you came in contact with water, and unlike neon you can’t be used to make lights which advertise the hot-ness, live-ness and nude-ness of people taking off their clothing, but you’re stable and geometrically regular. And that’s enough for me.