Quick Facts
| Property | Value |
|---|---|
| Symbol | N |
| Atomic Number | 7 |
| Atomic Mass | 14.007 u |
| Category | Nonmetal |
| Period | 2 |
| Group | 15 |
| Block | p |
| Electron Configuration | [He] 2s² 2p³ |
Physical Properties
| Property | Value |
|---|---|
| State at 20°C | Gas |
| Density | 0.001251 g/cm³ |
| Melting Point | -210.00°C (63.15 K) |
| Boiling Point | -195.79°C (77.36 K) |
| Appearance | Colorless, odorless gas |
Atomic Properties
| Property | Value |
|---|---|
| Electron Configuration | [He] 2s² 2p³ |
| Electronegativity | 3.04 (Pauling scale) |
| First Ionization Energy | 1402.3 kJ/mol |
| Atomic Radius | 65 pm |
| Covalent Radius | 71 pm |
| Van der Waals Radius | 155 pm |
History and Discovery
Discovered by: Daniel Rutherford Year of Discovery: 1772 Location: Edinburgh, Scotland
Etymology
The name "nitrogen" comes from the Greek words "nitron" (native soda) and "genes" (forming), meaning "niter-forming." The French name "azote" (still used in many languages) comes from Greek "a-" (without) and "zoe" (life), meaning "lifeless," as it does not support respiration.
Discovery Story
Daniel Rutherford discovered nitrogen in 1772 by removing oxygen and carbon dioxide from air and showing that the remaining gas could not support combustion or life. Carl Wilhelm Scheele, Henry Cavendish, and Joseph Priestley also studied nitrogen around the same time. Antoine Lavoisier recognized it as an element and named it "azote."
Isotopes
| Isotope | Natural Abundance | Half-life | Decay Mode |
|---|---|---|---|
| ¹⁴N | 99.636% | Stable | - |
| ¹⁵N | 0.364% | Stable | - |
Occurrence
Natural Abundance
Nitrogen makes up about 78.1% of Earth's atmosphere by volume, making it the most abundant uncombined element on Earth. It is the seventh most abundant element in the universe. In the Earth's crust, nitrogen is relatively rare (about 20 ppm), found mainly in nitrate minerals like saltpeter (KNO₃).
Extraction and Production
- Fractional Distillation of Air: Primary industrial method—air is liquefied and distilled
- Pressure Swing Adsorption: Separates nitrogen from air using molecular sieves
- Membrane Separation: Uses selective permeability of membranes
- Global production exceeds 150 million tons annually
Applications and Uses
Industrial Applications
- Ammonia production (Haber-Bosch process) for fertilizers
- Inert atmosphere for manufacturing and packaging
- Metal processing (annealing, hardening)
- Chemical synthesis
Technological Applications
- Electronics manufacturing (inert atmosphere)
- Tire inflation (maintains pressure better than air)
- Cryogenic cooling (liquid nitrogen at -196°C)
- Oil and gas well enhancement
Food Industry
- Modified atmosphere packaging (extends shelf life)
- Quick-freezing foods
- Preventing oxidation in food processing
Other Uses
- Fire suppression systems
- Cryopreservation of biological samples
- Superconductor cooling
- Special effects (fog production)
Biological Role
Nitrogen is essential for all life. It is a key component of amino acids, proteins, nucleic acids (DNA and RNA), and many other biological molecules.
In the Human Body
- About 3% of body mass is nitrogen
- Component of all proteins and nucleic acids
- Present in ATP (adenosine triphosphate)
- Essential for growth and repair
Nitrogen Cycle
Nitrogen cycles through the atmosphere, soil, and living organisms. Nitrogen fixation (by bacteria and lightning) converts N₂ to usable forms, while denitrification returns nitrogen to the atmosphere.
Dietary Sources
Nitrogen is obtained through protein-rich foods: meat, fish, eggs, dairy, legumes, and nuts.
Safety and Hazards
Toxicity
Nitrogen gas is non-toxic but can act as an asphyxiant by displacing oxygen. Nitrogen compounds vary widely in toxicity—some are essential nutrients while others are highly toxic.
Handling Precautions
- Can cause asphyxiation in confined spaces
- Liquid nitrogen causes severe frostbite on contact
- Nitrogen under pressure can cause decompression sickness ("the bends")
- Store liquid nitrogen in well-ventilated areas
Environmental Impact
Excess nitrogen from fertilizers causes eutrophication of waterways and dead zones in coastal waters. Nitrous oxide (N₂O) is a potent greenhouse gas and contributes to ozone depletion.
Interesting Facts
- Despite making up 78% of the atmosphere, nitrogen is relatively inert due to the strong triple bond in N₂
- Liquid nitrogen is cold enough to freeze almost anything solid
- The Haber-Bosch process for making ammonia fertilizer is estimated to support nearly half the world's food production
- Nitrogen narcosis ("rapture of the deep") affects divers at depths below 30 meters
- Plants cannot use atmospheric nitrogen directly—they need it "fixed" by bacteria or lightning