Periodic table › Krypton
1. Identity and classification
Colorless, odorless, tasteless monatomic gas; emits characteristic vivid glow in high-voltage plasma tubes
- Name and symbol
- Krypton (Krypton) · Kr
- Atomic number
- 36
- Relative atomic weight / mass number
- 83.798 ± 0.002
- Group · period · block
- 18 · 4 · p
- Category
- Noble Gas
- State near room temperature
- Gas
- Stable isotopes
- At least one stable isotope
- CAS number
- 7439-90-9
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
- 36 · 36
- Neutrons in reference isotope
- 48 (84Kr)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶- Abbreviated configuration
[Ar]4s² 3d¹⁰ 4p⁶- Electrons per shell
- 2, 8, 18, 8
- Listed oxidation states
- 0
- Electronegativity
- 3 (Pauling)
- First ionization energy
- 1350.795 kJ/mol · 14 eV
- Electron affinity
- Not established
- Covalent radius
- 116 pm
- van der Waals radius
- 202 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 0.003733 g/cm³
- Melting point
- 115.79 K · -157.36 °C · -251.248 °F
- Boiling point
- 119.93 K · -153.22 °C · -243.796 °F
- Crystal structure
- FCC
- Specific heat
- 0.248 J/(g·K)
- Thermal conductivity
- 0.00943 W/(m·K)
- Enthalpy of fusion
- 1.64 kJ/mol
- Enthalpy of vaporization
- 9.08 kJ/mol
- Magnetic ordering
- Diamagnetic
- Mohs hardness
- Not established
- Speed of sound
- 220 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
Closed valence shells explain low reactivity; xenon and krypton can form compounds under suitable conditions.
Selected compounds: Monatomic gas — no stable compounds at STP
Reaction reference
No ordinary reaction with air.
No ordinary reaction with water.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 78Kr | Stable | 0.355% | Stable |
| 80Kr | Stable | 2.286% | Stable |
| 82Kr | Stable | 11.593% | Stable |
| 83Kr | Stable | 11.500% | Stable |
| 84Kr | Stable | 56.987% | Stable |
| 85Kr | Radioactive | — | 10.739 Y |
| 86Kr | Stable | 17.279% | 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
- 1898 CE
- Scientists associated with discovery
- William Ramsay & Morris Travers
- Location
- United Kingdom (London)
- Origin
- Natural
- Listed crustal abundance
- Not established
Minerals and naming reference
Fractional distillation of liquid air (1.14 ppm in atmosphere)
Named from scientific/historical roots associated with Krypton (Kr), discovered or characterized by William Ramsay & Morris Travers.
7. Applications
High-intensity airport runway strobes, Krypton-Fluoride (KrF) excimer lasers for photolithography, energy-efficient window insulation
Detailed applications by field
- everyday
- High-intensity airport runway strobes, Krypton-Fluoride (KrF) excimer lasers for photolithography, energy-efficient window insulation
- industry
- Used in noble gas processing, specialized alloys, and chemical manufacturing (High-intensity airport runway strobes, Krypton-Fluoride (KrF) excimer lasers for photolithography, energy-efficient window insulation).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Krypton's electronic structure ([Ar] 3d¹⁰ 4s² 4p⁶) provides target conductivity.
- medicine
- Diagnostic imaging, biomedical instrumentation, or pharmaceutical synthesis research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Krypton.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Krypton.
- agriculture
- Soil geochemistry analysis, trace micronutrient research, or analytical environmental monitoring.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 4 p-block elements.
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
Classified as non-essential in human and biological systems.