All About Nitrogen

Podcast Transcript

If aliens were to look at the Earth through a telescope from far away and analyze our atmosphere, they would find that the dominant element is nitrogen.

Nitrogen makes up 78% of our atmosphere, and it’s all around us. However, it behaves very differently than the other common elements around us.

Nitrogen is not just vital for the functioning of life but is also used in various industrial and commercial applications as well.

Learn more about nitrogen, the invisible yet vital element, on this episode of Everything Everywhere Daily.

I’ve previously done episodes on the elements carbon and oxygen, which sit immediately on either side of nitrogen on the periodic table.

Nitrogen, despite being neighbors with each of those elements, behaves very differently.

Oxygen is very reactive, with six electrons in its outer shell. Carbon has four free electrons, which allows it to bond in a wide variety of ways with different elements.

Nitrogen has five free electrons. As with carbon and oxygen, understanding nitrogen involves understanding its atomic structure.

Nitrogen is the seventh element on the periodic table and the seventh most abundant element in the universe. With seven protons in its nucleus, it also has seven electrons. Two fill up its inner shell, and five are in the outer shell, which can hold up to eight.

That gives nitrogen three free electrons.

This is really the fundamental thing you need to know about nitrogen.

While I suppose you can say that is true with every element, in the case of nitrogen, it really likes to bond with other nitrogen atoms to form a nitrogen molecule or N₂.

When nitrogen bonds with itself, it creates a very strong triple covalent bond. More on this extremely important point in a bit.

While humans have been breathing nitrogen ever since they first existed, and while several nitrogen compounds, nitrogen as a separate element was unknown up until a few centuries ago.

The discovery of nitrogen is attributed to the Scottish chemist Daniel Rutherford, who identified a component in air that didn’t support combustion in 1772. Rutherford’s initial name for this gas was noxious air.

Rutherford didn’t know that his noxious gas was a separate element. The French chemist Antoine Lavoisier did experiments as well and found that any living thing subject to an atmosphere consisting only of this gas died. He called it mephitic air.

The English word comes from the French word nitrogène, which is a combination of nitre, which was a French word for saltpeter, and gene, from the Greek word for creation, as in Genesis.

As I noted in the introduction, nitrogen is the overwhelmingly dominant gas that makes up our atmosphere. 78% of the air you breathe is made up of nitrogen in molecular form.

However, because the atoms in a nitrogen molecule are bound so tightly with each other, for the most part, nitrogen acts like an inert gas. It doesn’t react with much because it is so hard to break the bonds within a nitrogen molecule.

The inertness of nitrogen molecules does have its uses. Nitrogen is the most commonly used gas used for preserving items. You pump in nitrogen to displace oxygen, and whatever it is you are trying to preserve will last longer without any oxygen to react with. This is most commonly done with food.

Many incandescent lightbulbs are filled with nitrogen so the filaments inside don’t quickly combust in the presence of oxygen.

Nitrogen is cheap and abundant, so it is preferable in most applications to truly inert gases like argon or helium.

However, as I also mentioned in the introduction, nitrogen is vital for life. Every amino acid, and hence every protein molecule, contains nitrogen.

If so much of nitrogen is tightly bound up with itself in the form of nitrogen molecules, how do life forms get access to nitrogen?

This is done through a process known as nitrogen fixation.

Nitrogen fixation is a crucial biological process that converts atmospheric nitrogen gas into ammonia or other nitrogen compounds that plants and other organisms can use.

Plants and animals cannot process atmospheric nitrogen molecules directly. They require it to be done by other means.

One way in which nitrogen is fixated, although it doesn’t account for much nitrogen fixation, is via lighting. Lighting strikes carry enormous energy that can break apart the nitrogen bonds and allow nitrogen to bond with oxygen to form nitrogen oxides.

However, the vast majority of nitrogen fixation on Earth is done via signal-cell organisms such as bacteria and archaea. These microbes are known as diazotrophic, and they are able to convert molecular nitrogen into usable forms via a class of enzymes known as Nitrogenases.

There are two types of diazotrophic microbes. The first are those that live free in the soil. They are not symbiotically attached to any plants, but the nitrogen they fixate is usable by any plants that happen to be nearby.

The other types are those that have symbiotic relationships with plants. Bacteria, such as Rhizobium and Bradyrhizobium, form symbiotic relationships with specific plants, often legumes such as soybeans, peas, and clover.

In these mutualistic relationships, the bacteria reside in specialized root nodules of the host plant. The plant provides the bacteria with sugars and other nutrients, while the bacteria convert atmospheric nitrogen into ammonia and provide it to the plant as a nitrogen source. In return, the plant benefits from increased nitrogen availability, which enhances its growth.

Once the plants consume the nitrogen, animals then eat the plants, and the free nitrogen is placed into the food chain.

Nitrogen is extremely important for plant growth and something that farmers have to take into consideration. If too many crops are planted in succession without nitrogen-fixing bacteria, the soil will eventually become exhausted of nitrogen.

This is one reason why many farmers practice crop rotation. In between crops such as corn or wheat, other nitrogen-fixing crops, such as legumes, add nitrogen to the soil. Sometimes, these crops aren’t even harvested. They are just plowed back into the ground to provide even more nutrients.

Crop rotation was not the only way that farmers would add nitrogen to the story. They would also fertilize the soil, usually through the addition of manure from farm animals or other byproducts like offal and blood.

Native Americans famously taught the early English settlers how to grow corn by planting each stalk on the remains of a fish, which provided the nitrogen for the plant.

However, as crop production grew in the 19th century, natural fertilizer was reaching its limits. There is only so much manure to go around. Guano, aka bird poop, deposits were mined around the world, but they were very limited resources.

By the start of the 20th century, there were concerns about the inability to provide enough nitrogen fertilizer to feed the world’s growing population.

The man who solved this problem was the German chemist Fritz Haber, on whom I’ve done a previous episode.

Haber developed a system for artificially taking atmospheric nitrogen and creating ammonia. In 1909, he was able to perform a laboratory demonstration that could produce drops of ammonia at a rate of 125 mL or four fluid ounces per hour.

Haber sold his invention to the German chemical company BASF who in turn gave Carl Bosh the assignment of scaling up the process so ammonia could be produced at an industrial scale.

Known as the Haber-Bosch process, it resulted in the creation of enough artificially fixated nitrogen that eliminated concerns about the ability to have enough fertilizer to feed the world.

Both Fritz Haber and Carl Bosch were awarded Nobel Prizes for their work.

While nitrogen is vital for agricultural crops, it is possible to have too much of a good thing.

When nitrogen fertilizer runs off of agricultural land, it can leech into the water supply and result in what is known as Eutrophication. Eutrophication is when a body of water becomes saturated with minerals and nutrients, particularly nitrogen.

This can result in algae blooms, which can deplete the oxygen in the water and kill most of the life forms that live in it.

While nitrogen fertilizer is an important use of nitrogen, it is far from the only one.

In many specialty cases, tires are often inflated with pure nitrogen instead of air. Oxygen can be reactive, and moisture in the air can cause excess expansion and contraction due to temperature. Race cars and airplanes will often inflate tires with nitrogen to solve these problems. Nitrogen tire inflation has even found its way to some commercial gas stations and auto repair centers.

Pure nitrogen gas is also used in a host of other applications where unwanted oxidation isn’t desired.

The process of nitriding is used on metals. Nitriding is a surface hardening process used to improve the hardness and wear resistance of metals, particularly steel. It involves the diffusion of nitrogen into the surface layers of the metal.

Nitrogen is used in some fire suppressant systems in lieu of carbon dioxide as well.

In the 19th century, one of the first artificial chemical creations using nitrogen was nitroglycerine. It is a highly volatile explosive that was used as the basis for dynamite.

One of the most important industrial and commercial uses of nitrogen is liquid nitrogen.

Nitrogen has a boiling point that can be reached relatively easily with commercial equipment. It will liquefy at ?196 °C, ??320 °F, or 77 kelvin.

Liquid nitrogen can be used for medical purposes for the removal of warts and other skin legions. I actually had this procedure performed on me when I was really young, and I had a wart on my hand. They injected a topical anesthesia and froze the offending wart with liquid nitrogen, which caused the area to shrivel and die.

Liquid nitrogen is used on metal parts to shrink them a small amount so they can better fit together and expand when they warm.

Many high-end classical musicians give their instruments cryogenic treatments. The process of making an instrument can result in microscopic fractures in the metal. By exposing the instruments to extreme cold temperatures provided by liquid nitrogen, many of the micro-fractures in the metal can heal.

Believe it or not, this technique also is used on woodwinds as well as brass instruments.

Liquid Nitrogen is used to cool the digital sensors in high-end astronomy telescopes. It is necessary to remove small heat fluctuations, which allow the instruments to be more sensitive to low light conditions.

One of the holy grails of physics and material science right now is to find a cheap, high-temperature superconductor. While a room-temperature superconductor would be ideal, even one that could operate at the temperature of liquid nitrogen could be made cost-effective for many uses.

Some high-end molecular gastronomy restaurants use liquid nitrogen to freeze foods and make ice cream.

Liquid nitrogen is normally safe to work with, but it can be very dangerous if used improperly.

When nitrogen boils and becomes a gas, it expands to 694 times the volume from when it was a liquid.

In 2006, there was an accident at Texas A&M University involving liquid nitrogen. A large tank of liquid nitrogen had a damaged pressure relief valve that didn’t allow the gas to vent. The pressure resulted in a catastrophic explosion which blew the tank through the ceiling and broke a concrete beam below it.

In 2012, a woman in England was hospitalized and had to have her stomach removed after she drank a cocktail made out of liquid nitrogen.

I find nitrogen to be a very odd element. It is everywhere and with us all the time, yet it is very difficult to work with beyond using it in its molecular form.

It is absolutely vital for all life, yet most life can’t access it directly.

It has a variety of industrial and commercial uses, but we couldn’t actually extract it from the air until the 20th century.

All of these apparent contradictions are what makes nitrogen so special.