Oxygen and Nitrogen Levels in the Atmosphere

Oxygen and nitrogen are two of a handful of elemental superstars of life. Without them, life would not be possible. In some ways, these two elements are very similar, but they are also very different.

Oxygen and nitrogen atoms differ in only one proton and one electron. In chemical reactions, the important subatomic particle is the electron, and oxygen has eight while nitrogen has seven. In the last two days, we talked about the difference that one electron makes. Oxygen and nitrogen make up about 99% of our atmosphere, with nitrogen composing nearly three-quarters of our air. So why is nitrogen’s percentage so high compared to oxygen?

As we said previously, the triple bond of a nitrogen molecule requires more than twice as much energy to break as the double bond of an oxygen molecule. The oxygen bond can be broken to allow combustion oxidation and energize our bodies. On the other hand, the nitrogen bond is not easy to break, but plants require nitrogen for photosynthesis and growth. What is the solution?

Lightning breaks the nitrogen bond allowing rain to wash nitrogen to the ground. Plants such as beans, peas, and alfalfa, which we call legumes, have microorganisms on their roots that extract nitrogen from the air. That enriches the soil with nitrogen while providing for the legumes. More than a century ago, scientists found a way to extract nitrogen from the air to produce ammonia. That process enabled fertilizer production, which today allows farmers to produce enough food for the world’s population.

It is not easy to break the nitrogen bond so it can combine with other elements, but with 78% of the atmosphere being nitrogen, there is no shortage. So why is our atmosphere mostly nitrogen? Since it is only about 21% oxygen, wouldn’t it be better to have more oxygen so we could breathe easier? The answer is that nitrogen stability is essential for our safety. Wildfires have been a significant problem in recent years. If the atmosphere consisted of a very high percentage of oxygen, fires would be more common and dangerous. If the atmosphere consisted of 100% oxygen, all it would take is one lightning strike to set the whole planet on fire.

Remarkably, we have the correct percentage of elements in our atmosphere. We have the right amount of oxygen to allow respiration to power our bodies and combustion to power our vehicles and industry and heat our homes. At the same time, we have the right amount of nitrogen to prevent uncontrolled combustion leading to the destruction of life. We have just a small amount of carbon dioxide, which plants need for photosynthesis. Plants use CO² and generate oxygen to keep the gases in balance. The balance is amazingly precise as long as humans don’t generate enough carbon dioxide to mess it up.

During the dinosaur age, the oxygen level was higher, on the order of around one-third of the atmosphere. That allowed the enormous animals to prepare the Earth for humans. Now we have the precise balance to sustain human life and advanced society. The question is, did the features of oxygen and nitrogen and the balance between them happen by accident, or was it part of an intelligent plan? We think the best explanation is that an intelligent Planner of life created it.

— Roland Earnst © 2022