Periodic table › Nitrogen
1. Identity and classification
Colorless, odorless, inert diatomic gas (N₂); colorless liquid below 77 K
- Name and symbol
- Nitrogen (Nitrogen) · N
- Atomic number
- 7
- Relative atomic weight / mass number
- 14.007 ± 0.001
- Group · period · block
- 15 · 2 · p
- Category
- Reactive Nonmetal
- State near room temperature
- Gas
- Stable isotopes
- At least one stable isotope
- CAS number
- 7727-37-9
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 7 · 7
- Neutrons in reference isotope
- 7 (14N)
- Full electron configuration
1s² 2s² 2p³- Abbreviated configuration
[He] 2s² 2p³- Electrons per shell
- 2, 5
- Listed oxidation states
- +5, +4, +3, +2, +1, -1, -2, -3
- Electronegativity
- 3.04 (Pauling)
- First ionization energy
- 1402.318 kJ/mol · 14.534 eV
- Electron affinity
- Not established
- Covalent radius
- 71 pm
- van der Waals radius
- 155 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 0.0012506 g/cm³
- Melting point
- 63.15 K · -210 °C · -346 °F
- Boiling point
- 77.36 K · -195.79 °C · -320.422 °F
- Crystal structure
- HCP
- Specific heat
- 1.04 J/(g·K)
- Thermal conductivity
- 0.02583 W/(m·K)
- Enthalpy of fusion
- 0.72 kJ/mol
- Enthalpy of vaporization
- 5.57 kJ/mol
- Magnetic ordering
- Diamagnetic
- Mohs hardness
- Not established
- Speed of sound
- 353 m/s
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
The N₂ triple bond is strong; nitrogen also forms many covalent compounds.
Selected compounds: NH₃ (Ammonia) · HNO₃ (Nitric acid) · NH₄NO₃ (Ammonium nitrate) · CO(NH₂)₂ (Urea) · TiN (Titanium nitride)
Reaction reference
Nitrogen is relatively unreactive at room temperature; high temperatures permit nitrogen oxide formation.
No direct reaction with liquid water under ordinary conditions.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 14N | Stable | 99.6205% | Stable |
| 15N | Stable | 0.3795% | Stable |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1772 CE
- Scientists associated with discovery
- Daniel Rutherford
- Location
- Scotland (Edinburgh)
- Origin
- Natural
- Listed crustal abundance
- 19 ppm
Minerals and naming reference
Chile saltpeter (NaNO₃), Niter (KNO₃); 78.08% by volume of Earth's atmosphere
From Greek 'nitron' (native soda/niter) + 'genes' (forming), coined by Jean-Antoine Chaptal in 1790
7. Applications
Food packaging modified atmosphere (keeping crisps/snacks fresh), automotive tire inflation
Detailed applications by field
- everyday
- Food packaging modified atmosphere (keeping crisps/snacks fresh), automotive tire inflation
- industry
- Haber process for ammonia and nitric acid, inert blanketing in chemical plants, stainless steel alloying
- electronics
- Dry nitrogen purging during integrated circuit manufacturing, GaN (Gallium nitride) LEDs and power transistors
- medicine
- Liquid nitrogen (LN₂) cryosurgery and cryopreservation of blood, stem cells, and embryos; N₂O anesthesia
- energy
- Pressurized gas accumulators, oil well enhanced recovery
- aerospace
- Fuel tank inerting systems in commercial aircraft, cold-gas attitude thrusters
- agriculture
- Synthesizing urea, ammonium nitrate, and NPK fertilizers that sustain global food production
- science
- 77 K cryogenic bath for high-temperature superconductors and spectroscopic detectors
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Essential component of all amino acids (proteins), nucleotides (DNA/RNA), ATP, and chlorophyll.