What Is Nitrogen?

Nitrogen is a chemical element with the symbol N and atomic number 7, classified as a nonmetal. It is the most abundant gas in Earth's atmosphere, making up about 78% of the air we breathe, yet despite this abundance, most living organisms can't directly use atmospheric nitrogen and instead depend on specialized bacteria or industrial processes to convert it into usable forms.

Nitrogen exists in the atmosphere as a diatomic molecule (N₂) held together by an extremely strong triple bond, which is precisely why nitrogen gas is so chemically unreactive under normal conditions despite the element's central importance to biology. Breaking that triple bond requires significant energy, which is exactly what makes industrial nitrogen fixation — converting N₂ into ammonia for fertilizer — such an energy-intensive but agriculturally essential process.

Nitrogen sits in Period 2, Group 15 of the periodic table. Its electron configuration of [He] 2s² 2p³ gives it five valence electrons, allowing it to form up to three covalent bonds, which is exactly how it achieves the stable triple bond holding N₂ molecules together.

Physical & Chemical Properties

Nitrogen has an atomic mass of 14.007 u and an extremely low gas density of 0.001145 g/cm³. It has a melting point of -210°C and a boiling point of -195.8°C, meaning it remains gaseous across virtually the entire range of temperatures found naturally on Earth.

In its diatomic gas form (N₂), nitrogen is remarkably unreactive due to the strength of the triple bond connecting its two atoms — one of the strongest chemical bonds known. This is something of a chemical paradox: nitrogen is essential to amino acids, proteins, and DNA, yet the form it exists in most abundantly (atmospheric N₂) is almost completely inert. Liquid nitrogen, produced by cooling the gas to below -196°C, is widely used as an extremely cold but chemically inert refrigerant, since it won't react with the materials it's used to freeze or preserve.

Electron Configuration Explained

Nitrogen's electron configuration is [He] 2s² 2p³, meaning it has the stable two-electron configuration of helium as its core, plus five additional electrons distributed across its second shell.

With three electrons in the 2p subshell (out of a possible six), nitrogen has exactly enough unpaired electrons to form three covalent bonds. When two nitrogen atoms combine to form N₂, each atom shares three electron pairs with the other, creating an unusually strong triple bond that locks both atoms into a remarkably stable, low-energy configuration — explaining why atmospheric nitrogen gas requires so much energy to break apart and react.

This same bonding capacity is also why nitrogen is central to amino acids and DNA: in biological molecules, nitrogen typically forms three single bonds rather than one triple bond, allowing it to link different atoms together within complex organic structures rather than simply pairing with another nitrogen atom.

History & Discovery

Nitrogen was discovered in 1772 by Scottish physician Daniel Rutherford, who identified it as the component of air that remained after oxygen and carbon dioxide had been removed, originally calling it "noxious air" because it couldn't sustain either combustion or animal life on its own. Several other scientists, including Carl Wilhelm Scheele and Henry Cavendish, conducted related experiments around the same period.

The element's modern name comes from the Greek words for "nitre-forming," referencing its presence in saltpeter (potassium nitrate), a substance long used in gunpowder production. The far greater significance of nitrogen — its essential role in proteins, DNA, and agricultural fertility — wasn't fully appreciated until decades later as biochemistry and agricultural science matured.

What Is Nitrogen Used For?

Nitrogen's properties make it essential across agriculture, industry, and food preservation:

  • Fertilizers: Synthetic nitrogen fertilizers, produced through the energy-intensive Haber-Bosch process, are credited with enabling the dramatic increases in agricultural yield that have fed much of the world's growing population over the past century.
  • Explosives: Many explosives, including TNT and dynamite, rely on nitrogen compounds that release energy rapidly when their chemical bonds break.
  • Cryogenic cooling: Liquid nitrogen's extremely low temperature and chemical inertness make it ideal for preserving biological samples, freezing food rapidly, and various medical and scientific cooling applications.
  • Food preservation: Nitrogen gas is used to displace oxygen in packaged foods, slowing spoilage and oxidation without introducing any reactive chemicals.
  • Airbags: Many vehicle airbags use a rapid chemical reaction that generates nitrogen gas to inflate almost instantly during a collision.

Common Nitrogen Compounds

Nitrogen forms numerous biologically and industrially important compounds:

  • Ammonia (NH₃): Produced industrially at massive scale for fertilizer production, and also a key building block for many other nitrogen compounds.
  • Amino acids and proteins: Every amino acid contains nitrogen, making it an essential element for all known life, since proteins built from amino acids perform most of the functional work inside living cells.
  • Nitrates: Compounds like potassium nitrate and ammonium nitrate are used extensively in fertilizers and, due to their oxidizing properties, in explosives.
  • Nitrous oxide (N₂O): Used medically as a mild anesthetic and pain reliever, commonly known as "laughing gas."

Fun Facts About Nitrogen

  • Despite making up 78% of the air we breathe, atmospheric nitrogen is so unreactive that most organisms — including humans — cannot directly use it, instead relying on nitrogen already converted into usable compounds through biological or industrial fixation.
  • Liquid nitrogen is cold enough to instantly freeze biological tissue, a property used both in medicine (such as removing skin lesions) and in popular science demonstrations involving instantly frozen flowers or fruit.
  • The Haber-Bosch process for industrially converting atmospheric nitrogen into ammonia fertilizer is estimated to support roughly half of the world's current food production, making it one of the most consequential chemical inventions in human history.
  • Nitrogen narcosis, sometimes called "the bends" in a related context, can affect deep-sea divers breathing compressed air, which is part of why specialized gas mixtures are used for very deep or prolonged dives.

Frequently Asked Questions

Why is nitrogen gas unreactive despite being essential to life?
Atmospheric nitrogen (N₂) is held together by an extremely strong triple bond that requires significant energy to break. While nitrogen atoms themselves are essential to amino acids and DNA, the diatomic gas form found in air is comparatively very stable and difficult to react.

What is nitrogen's atomic number?
Nitrogen has atomic number 7, meaning each nitrogen atom contains 7 protons in its nucleus.

Is liquid nitrogen dangerous?
Yes, liquid nitrogen's extreme cold (-196°C) can cause severe frostbite-like injuries on contact with skin, and it should always be handled with appropriate protective equipment and proper ventilation, since it can also displace breathable oxygen in enclosed spaces.

What is nitrogen used for in fertilizer?
Plants need nitrogen to build proteins and grow, but most plants can't use atmospheric N₂ directly. Nitrogen fertilizers provide nitrogen already converted into usable forms like ammonia or nitrates that plant roots can absorb.