7 N Nitrogen 14.007
Nonmetal p-block Period 2 Group 15

Nitrogen

N · Element 7 · Pnictogens

78% of the air you are breathing right now, held together by one of the strongest bonds in chemistry.

STATE AT 20°C Gas
ATOMIC MASS 14.007 u
ELECTRON CONFIGURATION [He] 2s² 2p³
6C All 118 8O

Structure

The nitrogen atom

Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.

Orbital cloud

Measured values

Property sheet

Every bar shows where nitrogen sits among all 118 elements for that property.

Physical

Density 0.001 g/cm³ 3%
Melting point 63.2 K 5%
Boiling point 77.4 K 3%
Specific heat 1.04 J/g·K
Thermal conductivity 0.03 W/m·K 6%

Atomic

Atomic radius 65 pm 4%
Covalent radius 71 pm
Van der Waals radius 155 pm

Electronic

Electronegativity 3.04 97%
Ionisation energy 1401.9 kJ/mol 97%
Electron affinity 0 kJ/mol 0%

Occurrence

Abundance in crust 19 mg/kg 71%

Identity

SymbolN
Atomic number7
Atomic mass14.007 u
CategoryNonmetal
Blockp
Crystal structurehexagonal
Oxidation states-3, -2, -1, +1, +2, +3, +4, +5
Discovered1772
Discovered byDaniel Rutherford

Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.

Size, to scale

How big is a nitrogen atom?

Radius 65 pm — that is 0.065 nm, so about 7692 million of them side by side would span a millimetre.

Thermal range

Solid, liquid, gas — and when

Nitrogen is liquid over a 14 K window, from 63 K to 77 K.

Where it sits

Position in the table

Nitrogen sits in period 2, group 15. Everything in group 15 shares the same outer-electron count, which is why they behave so similarly.

OTHER NONMETALS

1H 6C 8O 15P 16S 34Se
All nonmetals

The story

What nitrogen is, and how we found it

The Essential Element of Life

Nitrogen is the most abundant element in Earth's atmosphere, comprising approximately 78% of the air we breathe. This colorless, odorless, and generally inert gas is fundamental to all living organisms, forming the backbone of amino acids, proteins, and nucleic acids like DNA and RNA.

Despite its abundance, nitrogen in its molecular form (N₂) is remarkably unreactive due to the extremely strong triple bond between the two nitrogen atoms. This chemical inertness makes nitrogen useful as an inert atmosphere for industrial processes, but also means that most organisms cannot directly use atmospheric nitrogen for biological processes.

Fun Fact: The nitrogen cycle is one of the most important biogeochemical cycles on Earth, involving the conversion of nitrogen between its various chemical forms through biological, chemical, and physical processes.

Nitrogen compounds are essential for agriculture, with nitrogen-based fertilizers being crucial for modern food production. However, nitrogen can also form dangerous compounds - nitrogen oxides contribute to air pollution and acid rain, while nitrogen-containing explosives have shaped military history.

In industry, liquid nitrogen (at -196°C) serves as an ultra-cold refrigerant, used in everything from food preservation to medical procedures. The element's dual nature - essential for life yet potentially dangerous in certain forms - makes nitrogen one of the most fascinating elements on the periodic table.

Applications

What nitrogen is used for

Industrial Applications and Manufacturing

Haber-Bosch Process and Fertilizer Production

The largest industrial use of nitrogen is in the Haber-Bosch process, which converts atmospheric nitrogen into ammonia (NH₃). This significant process, developed in the early 20th century, involves reacting nitrogen with hydrogen under high pressure (150-200 atm) and temperature (400-500°C) using an iron catalyst:

N₂ + 3H₂ → 2NH₃

This process produces over 150 million tons of ammonia annually, with approximately 80% used to manufacture nitrogen-based fertilizers including:

  • Ammonium nitrate (NH₄NO₃) - High-nitrogen content fertilizer
  • Urea (CO(NH₂)₂) - World's most widely used nitrogen fertilizer
  • Ammonium sulfate ((NH₄)₂SO₄) - Provides both nitrogen and sulfur
  • Ammonium phosphate - Combines nitrogen with phosphorus

Chemical Manufacturing and Synthesis

Nitrogen serves as a critical feedstock for producing numerous industrial chemicals:

  • Nitric acid (HNO₃) - Produced via the Ostwald process, used in explosives, fertilizers, and chemical synthesis
  • Hydrogen cyanide (HCN) - Essential for producing adiponitrile, which becomes nylon
  • Melamine - Used in producing melamine-formaldehyde resins for laminates and adhesives
  • Acrylonitrile - Building block for synthetic fibers and plastics

Cryogenic and Cooling Applications

Liquid nitrogen at -196°C (-321°F) provides ultra-low temperature cooling for:

  • Food processing - Flash-freezing foods to preserve texture and nutrients
  • Medical applications - Cryosurgery, cryotherapy, and preserving biological samples
  • Electronics manufacturing - Cooling superconductors and testing electronic components
  • Laboratory research - Creating controlled low-temperature environments
  • Transportation - Shrink-fitting metal parts and maintaining vaccine cold chains

Metallurgy and Material Processing

Nitrogen creates inert atmospheres to prevent oxidation during:

  • Steel production - Preventing carbon loss and controlling steel properties
  • Aluminum welding - Protecting welds from atmospheric contamination
  • Heat treatment - Controlling atmosphere during annealing and hardening
  • Powder metallurgy - Preventing oxidation during sintering processes

Electronics and Semiconductor Industry

High-purity nitrogen is essential for:

  • Wafer processing - Creating clean, oxygen-free environments
  • Chemical vapor deposition - Depositing thin films without contamination
  • Soldering operations - Preventing oxidation of electronic components
  • Storage and transport - Maintaining inert conditions for sensitive materials

Everyday Applications and Consumer Products

Food Industry and Preservation

  • Modified Atmosphere Packaging (MAP) - Extends shelf life of fresh produce, meats, and baked goods by replacing oxygen with nitrogen
  • Wine and Beer Production - Nitrogen prevents oxidation during fermentation, storage, and bottling
  • Coffee Packaging - Nitrogen-flushed coffee bags maintain freshness by eliminating oxygen
  • Cooking and Food Service - Liquid nitrogen creates dramatic effects in molecular gastronomy
  • Potato Chip Bags - Nitrogen-filled packages prevent rancidity and maintain crispiness
  • Oil and Fat Processing - Nitrogen blanketing prevents oxidation during production and storage

Automotive and Transportation

  • Tire Inflation - Pure nitrogen maintains consistent tire pressure longer than air
  • Formula 1 Racing - Nitrogen-filled tires provide more predictable pressure changes
  • Aircraft Tires - Nitrogen prevents tire fires and maintains pressure at altitude
  • Fuel Tank Inerting - Military and commercial aircraft use nitrogen to prevent fuel tank explosions

Medical and Healthcare Applications

  • Dermatology - Liquid nitrogen removes warts, skin tags, and precancerous lesions
  • Cryotherapy - Whole-body cryotherapy chambers use nitrogen for athletic recovery
  • Organ Preservation - Liquid nitrogen stores organs, tissues, and medical samples
  • Pharmaceutical Manufacturing - Nitrogen atmospheres prevent degradation during drug production
  • Medical Device Packaging - Nitrogen prevents corrosion of surgical instruments

Laboratory and Research

  • Sample Storage - Liquid nitrogen dewars preserve biological samples for very long periods
  • Chemical Reactions - Nitrogen atmospheres prevent unwanted oxidation reactions
  • Analytical Chemistry - Nitrogen serves as carrier gas in gas chromatography
  • Vacuum Systems - Nitrogen purging removes residual gases from vacuum chambers

Environmental and Safety Applications

  • Fire Suppression - Nitrogen-based fire suppression systems protect data centers and museums
  • Tank Cleaning - Nitrogen inerting prevents explosions during fuel tank maintenance
  • Pipeline Purging - Nitrogen removes flammable gases before maintenance work
  • Oil Spill Response - Nitrogen prevents ignition during cleanup operations

Where it comes from

Natural occurrence

19 mg/kg of Earth's crust · more abundant than 71% of elements

Abundance and Natural Sources

Atmospheric Abundance

Nitrogen dominates Earth's atmosphere, comprising approximately 78.08% of the air by volume. This massive reservoir contains an estimated 3.9 × 10¹⁵ tons of nitrogen gas (N₂), making it the most abundant uncombined element accessible to life on Earth.

The atmospheric nitrogen exists primarily as diatomic molecules (N₂) held together by an extremely strong triple bond (941 kJ/mol), making it one of the most chemically inert substances under normal conditions. This stability explains why atmospheric nitrogen has accumulated over billions of years.

Stellar Nucleosynthesis and Cosmic Origin

Nitrogen is formed in the cores of massive stars through stellar nucleosynthesis via two primary processes:

  • CNO Cycle - Carbon-nitrogen-oxygen fusion cycle that powers stars more massive than our Sun
  • Stellar Wind Processing - Secondary processes in evolved stars that enrich the interstellar medium
  • Supernova Nucleosynthesis - Explosive stellar death creates and distributes nitrogen throughout galaxies

In the universe, nitrogen ranks as the 7th most abundant element, with an estimated cosmic abundance of about 1 part per 1,000 hydrogen atoms.

Geological Occurrence and Crustal Abundance

Within Earth's crust, nitrogen is relatively rare, comprising only about 0.002% by weight. Natural nitrogen-bearing minerals include:

  • Saltpeter (Potassium nitrate, KNO₃) - Forms in arid regions through bacterial processes
  • Chile saltpeter (Sodium nitrate, NaNO₃) - Large deposits in the Atacama Desert
  • Niter (Potassium nitrate) - Found in caves and soil in limestone regions
  • Organic deposits - Coal, petroleum, and natural gas contain nitrogen compounds

Biological Nitrogen Cycle

The nitrogen cycle represents one of Earth's most crucial biogeochemical processes:

Nitrogen Fixation

Special bacteria convert atmospheric N₂ into biologically available forms:

  • Rhizobium bacteria - Symbiotic relationship with legume plant roots
  • Azotobacter - Free-living soil bacteria
  • Cyanobacteria - Blue-green algae in aquatic environments
  • Lightning - Natural electrical discharge creates nitrogen oxides

Nitrification and Denitrification

Soil bacteria continuously transform nitrogen between various oxidation states:

  • Ammonification - Decomposition releases ammonia from organic matter
  • Nitrification - Conversion of ammonia to nitrites then nitrates
  • Denitrification - Return of nitrates to atmospheric nitrogen

Marine and Aquatic Systems

Ocean and freshwater systems contain significant dissolved nitrogen:

  • Dissolved N₂ - Approximately 15 mg/L in seawater at standard conditions
  • Nitrates and nitrites - Essential nutrients for marine phytoplankton
  • Organic nitrogen - Proteins and nucleic acids in marine organisms
  • Hydrothermal vents - Specialized bacteria fix nitrogen in deep ocean environments

Human Impact on the Nitrogen Cycle

Human activities have dramatically altered the global nitrogen cycle:

  • Industrial nitrogen fixation - Haber-Bosch process doubles natural nitrogen fixation
  • Agricultural runoff - Excess fertilizers cause eutrophication in water bodies
  • Fossil fuel combustion - Releases nitrogen oxides contributing to air pollution
  • Deforestation - Disrupts natural nitrogen cycling in forest ecosystems

Handling

Safety

Safety Information and Handling Precautions

DANGER: Nitrogen gas can cause rapid asphyxiation without warning. In confined spaces, nitrogen displaces oxygen and can lead to unconsciousness and death within seconds.

Asphyxiation Hazards

Nitrogen gas toxicity: While nitrogen itself is low-toxicity, it poses severe asphyxiation risks:

  • Oxygen displacement - Nitrogen reduces oxygen concentration below safe levels (16% minimum)
  • No warning signs - Victims may lose consciousness without experiencing difficulty breathing
  • Rapid onset - Unconsciousness can occur within 1-2 breaths in high-concentration environments
  • Silent killer - Colorless, odorless gas provides no sensory warning

Cryogenic Hazards (Liquid Nitrogen)

EXTREME COLD: Liquid nitrogen at -196°C can cause severe frostbite and tissue damage within seconds of contact.

Cryogenic safety measures:

  • Personal protective equipment - Insulated gloves, safety glasses, and long pants required
  • Skin contact - Can cause instantaneous frostbite and permanent tissue damage
  • Eye protection - Splash protection essential to prevent corneal freezing
  • Vapor expansion - One liter of liquid nitrogen expands to 694 liters of gas
  • Pressure buildup - Closed containers can explode due to rapid expansion

Industrial Safety Standards

OSHA regulations and workplace limits:

  • Oxygen monitoring - Required in areas where nitrogen is used or stored
  • Ventilation systems - Adequate air circulation prevents oxygen depletion
  • Emergency procedures - Rescue protocols for nitrogen-related incidents
  • Training requirements - Workers must understand asphyxiation risks
  • Atmospheric testing - Continuous monitoring in confined spaces

Storage and Transportation

Safe handling procedures:

  • Cylinder storage - Secure upright storage away from heat sources
  • Pressure relief - Containers must have appropriate pressure release systems
  • Transport regulations - DOT regulations for shipping compressed and cryogenic nitrogen
  • Leak detection - Regular inspection of storage and transfer equipment
  • Emergency response - Proper procedures for nitrogen leaks or exposures

First Aid and Emergency Response

Immediate response procedures:

  • Asphyxiation - Move victim to fresh air immediately, provide artificial respiration if needed
  • Cryogenic burns - Remove from cold source, warm affected area gradually with lukewarm water
  • Eye contact - Flush with lukewarm water for 15 minutes, seek immediate medical attention
  • Emergency contacts - Poison control: 1-800-222-1222, Emergency services: 911

Environmental Considerations

Environmental impact and regulations:

  • Nitrogen oxides - Contribute to acid rain and ozone formation
  • Eutrophication - Excess nitrogen causes algal blooms and aquatic ecosystem disruption
  • Greenhouse effects - Nitrous oxide (N₂O) is a potent greenhouse gas
  • Agricultural runoff - Nitrogen fertilizers contribute to water pollution
  • Waste disposal - Proper disposal methods for nitrogen-containing compounds

Quick answers

Nitrogen: common questions

What is Nitrogen?

Nitrogen (symbol N) is element 7 on the periodic table, a nonmetal in period 2, group 15. 78% of the air you are breathing right now, held together by one of the strongest bonds in chemistry. At room temperature it is a gas.

What is the electron configuration of Nitrogen?

Nitrogen's ground-state electron configuration is [He] 2s² 2p³, giving 2 occupied shells holding 2, 5 electrons respectively. Its outer shell holds 5 electrons, which is what sets its bonding behaviour.

What are the melting and boiling points of Nitrogen?

Nitrogen melts at 63.2 K (-210 °C) and boils at 77.4 K (-195.8 °C).

What is the atomic mass of Nitrogen?

The standard atomic weight of Nitrogen is 14.007 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.

How dense is Nitrogen?

Nitrogen is a gas at room temperature; its density is about 1.3 g/L at 0 °C and 1 atm — roughly heavier than air.

What is the electronegativity of Nitrogen?

Nitrogen has a Pauling electronegativity of 3.04. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). A value this high means it tends to pull electrons away from almost anything it bonds with.

Who discovered Nitrogen, and when?

Nitrogen was discovered in 1772 by Daniel Rutherford. It is named after greek nitron + genes, "niter-forming".

How common is Nitrogen on Earth?

Nitrogen makes up about 19 mg/kg of the Earth's crust — uncommon, but not rare.

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