Nitrogen

Nitrogen makes up a whopping 78% of the air we breathe, but for a long time, no one knew it existed! Back in the 1760s and 70s, chemists such as Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley were trying to figure out what air was made of. They knew about oxygen, but there was still something else in the air that they couldn’t define. When they removed oxygen from the air, they found that the remaining gas couldn’t keep candles burning or support life. Mice placed in this mysterious air didn’t survive, so they called it names like "noxious air" and "burnt air." These properties provided clues, but no one realized they had discovered nitrogen.

The real breakthrough came in 1772 when Daniel Rutherford, a Scottish physician, isolated nitrogen from the air and suggested it might be a new element. While Rutherford didn’t fully understand what he had found, his work laid the groundwork for future discoveries. A few years later, in 1785, Henry Cavendish correctly determined that air was made of four parts nitrogen and one part oxygen, but he still didn’t use the word “nitrogen” to describe this mysterious gas.

The name "nitrogen" came about in 1790, thanks to French chemist Jean-Antoine Chaptal. He named the element "nitrogène," which means "nitre-forming." Nitre, or potassium nitrate (also called saltpeter), was important because it was used to make nitric acid and gunpowder. The word has roots in both Greek and Latin, and Chaptal's name stuck in English as well, entering the language as "nitrogen" in 1794. Another early name for nitrogen was "azote," meaning “no life” in Greek, because it couldn’t support breathing or combustion. This name is still used in many languages today.

Before the element itself was understood, nitrogen compounds had been used for centuries. Ancient civilizations knew about ammonium chloride, and during the Middle Ages, alchemists worked with nitric acid and nitrate salts. They even created a powerful acid called aqua regia, a mixture of nitric and hydrochloric acids, famous for being able to dissolve gold, the "king of metals." Nitrogen compounds also became essential for making gunpowder and fertilizers, giving nitrogen a starring role in agriculture and warfare.

By the early 20th century, scientists developed methods to produce nitrogen compounds on a large scale. The Haber-Bosch process, invented in the early 1900s, allowed industries to fix nitrogen (or capture it) from the air, creating synthetic fertilizers. This was a game-changer for farming, and today, about half of the world’s food production depends on these fertilizers. At the same time, nitrogen compounds became important in manufacturing explosives, playing a huge role in both World Wars. From ancient alchemy to modern industry, nitrogen has played a vital role in warfare, agriculture, and scientific advancements.

Nitrogen is a nonmetal that, in its gas or liquid state, is clear and odorless. N₂ has a very strong covalent triple bond, one of the strongest bonds in all of chemistry. This has two main consequences:

First, it is very difficult to extract nitrogen from atmospheric gas, although it is possible. Some soil bacteria have evolved to do it, naturally fertilizing plants. And human industry does it by the “Haber-Bosch process”—a high-pressure, metal-catalyzed reaction of N₂ with H₂. The rest is done by lightning.

Second, there’s a ton of energy stored in N₂’s strong triple bond. When nitrogen compounds convert or decompose to N₂ gas, the triple bond breaks and releases a massive amount of energy. This is why many nitrogen compounds are valuable as explosives, like TNT (trinitrotoluene) and dynamite (with a nitroglycerin base).

Nitrogen on its own has many uses. As a gas, it serves as an inert atmosphere (no oxygen) for preserving food, processing steel and stainless steel, and manufacturing electronic components. As a compressed gas, it is used to pressurize containers, like beer kegs and paintball guns. As a liquid, it looks like water. It is a cryogenic refrigerant with many uses, including freezing food for freshness. It also has medical uses, such as freezing blood, eggs, and sperm for preservation or freezing warts and cysts to remove them.

Nitrogen also has valuable compounds, particularly ammonia (NH3). It is an important fertilizer—a critical precursor to the production of nearly half of the world's food supply. It is also a common solvent and glass cleaner, but it has more specialized applications too, such as rocket fuel. Other nitrogen compounds are used as fertilizers and rocket fuels as well.

Nitrogen is also a key component of major biomolecules, including DNA and enzymes. It is likewise used in every major class of pharmaceuticals.

Commercially, ammonia is the most important nitrogen compound. It is useful on its own or as a precursor to making other nitrogen compounds. These include nitric acid (HNO₃) and potassium and sodium nitrate (saltpeter and Chile saltpeter, KNO₃ and NaNO₃, respectively). These, like other nitrogen compounds, are used variously as food preservatives, fertilizers, explosives, propellants, and more.

Nitrogen, produced in stars, is the seventh most abundant element in the universe. It is the largest component of the earth’s atmosphere and one of the main constituents of the human body. However, it is not abundant in the earth’s crust. There, it makes up only 0.0019 percent, similar to lithium, niobium, and gallium.

The primary commercial source of nitrogen is air. Air is liquefied and then distilled to isolate nitrogen. That means the liquefied air is heated until one component evaporates and is collected. Then it is heated further until the next component evaporates, and so on.