Nitrogen · element 7
Four fifths of every breath you take, yet your body cannot use a single atom of it directly
Key facts
Take a breath. About 78 per cent of what just entered your lungs was nitrogen, and almost all of it will leave again unchanged. Nitrogen gas is made of pairs of atoms held together by a triple bond, one of the strongest in chemistry. That bond makes nitrogen so stable that most things ignore it, which is exactly why it fills the air rather than reacting away.
Yet nitrogen is essential. Every amino acid, every protein and every base in DNA contains it. The challenge for living things is breaking that triple bond to get at the atoms. Only certain bacteria and lightning can do it naturally. In the twentieth century humans learned to do it industrially, and that single invention now feeds roughly half the world.
Where it is found
The atmosphere is nitrogen's great reservoir. It makes up about 78 per cent of dry air by volume, a store vastly larger than all the nitrogen in soil, rocks and living things combined. The main mineral sources are nitrate deposits such as those in the Atacama Desert of Chile, which were once mined intensively for fertiliser and explosives, and potassium nitrate, or saltpetre, which forms in caves and old manure heaps.
Living things hold a constantly cycling stock of nitrogen. Bacteria in soil and in the root nodules of peas, beans and clover convert nitrogen gas into ammonia, which plants build into proteins. Other bacteria return it to the air. Beyond Earth, Saturn's moon Titan has a thick atmosphere that is mostly nitrogen, and Pluto's thin one is too.
How it was discovered
In 1772 Daniel Rutherford, a medical student in Edinburgh, burned substances in a sealed volume of air, absorbed the carbon dioxide produced, and studied the gas that remained. Nothing would burn in it and a mouse could not live in it. He called it noxious air. Several other chemists, including Scheele, Cavendish and Priestley, were investigating the same gas at about the same time, but Rutherford published first and usually receives the credit.
Antoine Lavoisier named it azote, meaning without life, a name still used in French. The English name came from Jean-Antoine Chaptal in 1790. He chose nitrogen, meaning nitre-former, because the gas was found to be a component of nitre, the old name for potassium nitrate.
What we use it for
The Haber-Bosch process, developed just before the First World War, combines nitrogen from the air with hydrogen under high pressure to make ammonia. That ammonia becomes the nitrogen fertiliser that underpins modern farming. The same chemistry supplies nitric acid for explosives, dyes and nylon.
Nitrogen gas is valuable precisely because it does so little. It fills crisp packets and food containers to keep oxygen out, blankets flammable chemicals in storage and inflates aircraft tyres. Liquid nitrogen, at about minus 196 degrees Celsius, freezes food quickly, preserves biological samples, cools scientific instruments and is used by dermatologists to remove warts.
Reading the numbers
Nitrogen boils at about minus 196 degrees Celsius and freezes at about minus 210. That boiling point is cold enough to make liquid nitrogen an everyday coolant, yet warm enough that it can be made cheaply by liquefying air. As a gas its density is 1.25 grams per litre, very slightly less than air, which is unsurprising since air is mostly nitrogen.
The configuration [He] 2s2 2p3 gives nitrogen five outer electrons, three short of a full shell. Two nitrogen atoms can each share three electrons to form a triple bond, and that is the source of N2's famous stability. Nitrogen's electronegativity of 3.04 is high, so it pulls electrons towards itself in compounds with hydrogen and carbon. Its first ionisation energy of 1402 kilojoules per mole is higher than oxygen's, an effect of its neat half-filled set of p orbitals. Nitrogen heads group 15 in period 2.
Safety and the environment
Nitrogen gas is not toxic, but it is a silent suffocation hazard. If it displaces the oxygen in a confined space, a person can lose consciousness in seconds without feeling short of breath. Liquid nitrogen causes instant frostbite on skin and expands almost seven hundred times when it boils, so it must never be sealed in a closed container.
Environmentally, the story is about too much of a good thing. Nitrogen fertiliser washed from fields feeds algal blooms in rivers and coastal seas, creating dead zones where fish cannot live. Nitrous oxide from soils is a potent greenhouse gas. Managing the nitrogen cycle is one of the great environmental challenges of this century.
Did you know?
- About 78 per cent of the air by volume is nitrogen.
- The triple bond in a nitrogen molecule is one of the strongest chemical bonds known, which is why nitrogen gas is so unreactive.
- Nitrogen fertiliser made by the Haber-Bosch process is estimated to feed around half of the world's population.
- Liquid nitrogen boils at about minus 196 degrees Celsius and is used to freeze off warts and to make instant ice cream.
- Saturn's largest moon Titan has an atmosphere thicker than Earth's that is mainly nitrogen.
- The decompression sickness that divers call the bends is caused by nitrogen bubbling out of the blood as pressure falls.
More in the non-metals
Column-mates come first, since elements in one column have outer electrons arranged in a similar way and tend to behave alike; the rest are the nearest neighbours in the family.
See all 7 non-metals on one page, or browse all 118 elements.
Compare Nitrogen with another element
Each comparison has a side-by-side data table and a plain-English summary of the differences.
Frequently asked questions
Is nitrogen flammable?
No. Nitrogen gas does not burn and does not support burning; a flame goes out in it. That is why it is used to blanket flammable liquids and to fill packaging. Some nitrogen compounds, such as ammonia and nitroglycerine, are a different matter.
Why do we breathe nitrogen if we do not use it?
We breathe it simply because it is there. Nitrogen gas passes in and out of the lungs unchanged, because the body has no way to break its triple bond. All the nitrogen in our proteins comes from food, and ultimately from plants and bacteria that can fix it.
How cold is liquid nitrogen?
It boils at about minus 196 degrees Celsius, roughly 77 kelvin. Anything dipped into it freezes almost instantly, and it causes severe frostbite on contact with skin. It must be stored in vented containers because it expands enormously as it turns back into gas.
Why is nitrogen important for plants?
Plants need nitrogen to make proteins, chlorophyll and DNA. They cannot take it from the air, so they absorb nitrate or ammonium from the soil, supplied by bacteria, decaying matter or fertiliser. Nitrogen shortage shows as pale, stunted growth.
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Written by Anthony. Updated September 2026. Numerical data from Periodic-Table-JSON (CC BY-SA), cross-checked against the Nitrogen reference article. Spotted an error? Tell us.