Nitrogen
Atomic Data
| Atomic Number | 7 |
| Symbol | N |
| Atomic Weight | 14.007 u |
| Density (STP) | 1.2506 g/L |
| Melting Point | −210.0 °C (63.15 K) |
| Boiling Point | −195.79 °C (77.36 K) |
| Electronegativity | 3.04 (Pauling) |
| Electron Config. | 1s2 2s2 2p3 |
| Oxidation States | −3, −2, −1, 0, +1, +2, +3, +4, +5 |
| Phase at STP | Gas |
| Category | Reactive Nonmetal |
| Period / Group | 2 / 15 |
| CAS Number | 7727-37-9 |
Electron Configuration
[He] 2s2 2p3
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 3 | 7 |
| Total | 7 | 7 | ||
Isotopes of Nitrogen
Nitrogen has two naturally occurring stable isotopes. The most abundant is ¹⁴N, comprising 99.636% of all naturally occurring Nitrogen.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Nitrogen-14 | ¹⁴N | 7 | 7 | 99.636 | Stable |
| Nitrogen-15 | ¹⁵N | 7 | 8 | 0.364 | Stable |
Abundance & Occurrence
Nitrogen is present in Earth's crust at approximately 19 ppm by mass and at approximately 1000 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Asphyxiation: Nitrogen is a colourless, odourless, tasteless gas that displaces oxygen; concentrations above ~85% in air cause rapid unconsciousness and death without warning — the leading cause of fatalities in industrial gas accidents.
- Liquid nitrogen cryogenic burns: Liquid nitrogen at −196 °C causes immediate, severe cryogenic burns to skin and eyes on contact; insulated gloves and face protection are mandatory, and sealed containers must never be used.
- Rapid vaporisation: One litre of liquid nitrogen expands to approximately 694 litres of gas at room temperature; spills in enclosed spaces can instantly produce a lethal, oxygen-deficient atmosphere.
- Pressurised systems: Nitrogen at high pressure is used to purge pipelines and inert storage vessels; purged vessels must be verified oxygen-sufficient before entry — confined-space entry procedures are mandatory.
Nitrogen in the Real World
Real-World Uses
- Fertiliser production — The Haber-Bosch process fixes atmospheric nitrogen into ammonia, which is the starting material for virtually all synthetic nitrogen fertilisers (urea, ammonium nitrate, ammonium sulfate) that underpin modern agriculture.
- Food packaging — Nitrogen gas flushes oxygen from food packaging to prevent oxidation and microbial growth, extending the shelf life of crisps, nuts, coffee, and other perishable products.
- Cryogenic freezing — Liquid nitrogen (−196 °C) is used to snap-freeze biological samples, sperm, embryos, and tissue for long-term storage in biobanks, and to rapidly freeze food products to preserve texture and quality.
- Electronics manufacturing — Nitrogen provides an inert reflow-soldering atmosphere in circuit board assembly and purges semiconductor furnaces during diffusion and oxidation steps, preventing unintended oxidation.
- Explosives — Nitrogen-rich compounds such as TNT, RDX, ammonium nitrate, and nitroglycerin release large volumes of gas rapidly upon detonation, used in mining, demolition, and military applications.
- Tyre inflation — Pure nitrogen is used to inflate aircraft tyres and racing car tyres because it does not contain moisture, reducing pressure variation with temperature and slowing rubber oxidation from the inside.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is nitrogen used for?
Nitrogen has many important industrial uses. The Haber-Bosch process converts nitrogen gas to ammonia for synthetic fertilisers. Liquid nitrogen is used as a cryogenic coolant for storing biological samples, food freezing, and superconductor cooling. Nitrogen provides inert atmospheres in electronic manufacturing, food packaging, and metallurgical heat treatment. Nitrogen compounds are also central to explosives, pharmaceuticals, and dyes.
Why does nitrogen make up most of the atmosphere?
Nitrogen (N₂) makes up 78% of Earth’s atmosphere primarily because it is chemically very stable — the N≡N triple bond is one of the strongest in chemistry, requiring extreme conditions (lightning, industrial catalysts, or biological enzymes) to break. This stability means that unlike oxygen and carbon dioxide, nitrogen does not react readily with rocks or water to be removed from the air, allowing it to accumulate over geological time.
Is nitrogen essential for life?
Yes, nitrogen is indispensable to life. It is a component of amino acids (the building blocks of proteins), nucleic acids (DNA and RNA), and ATP. Animals obtain nitrogen by eating protein; plants absorb nitrate and ammonium ions from soil; some bacteria and cyanobacteria can fix atmospheric N₂ directly into ammonium, making it available to the ecosystem. Without the nitrogen cycle, life as we know it could not exist.
Is liquid nitrogen dangerous?
Liquid nitrogen (boiling point −196°C) is hazardous in several ways. Contact with skin or eyes causes cryogenic burns and frostbite almost instantly. Rapid vaporisation in a sealed container can cause explosive pressure build-up. Most critically, liquid nitrogen vaporising in a confined space rapidly displaces oxygen, creating an asphyxiation hazard that can be fatal without warning because nitrogen is colourless and odourless. Proper ventilation and cryogenic personal protective equipment are essential.