Krypton (Kr)
Stable isotopes of krypton available from ISOFLEX
| Isotope | Z(p) | N(n) | Atomic Mass | Natural Abundance | Enrichment Level | Chemical Form |
| Kr-78 | 36 | 42 | 77.92039 | 0.35% | 99.90% | Gas |
| Kr-80 | 36 | 44 | 79.916379 | 2.25% | 99.90% | Gas |
| Kr-82 | 36 | 46 | 81.913485 | 11.60% | 99.90% | Gas |
| Kr-83 | 36 | 47 | 82.914137 | 11.50% | 99.90% | Gas |
| Kr-84 | 36 | 48 | 83.911508 | 57.00% | 99.90% | Gas |
| Kr-86 | 36 | 50 | 85.910615 | 17.30% | 99.90% | Gas |
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Krypton was discovered in 1898 by Sir William Ramsay and Morris W. Travers. Its name originates with the Greek word kryptos, meaning “hidden.”
Krypton is a colorless, odorless, tasteless gas. It liquefies at -153.22 ºC and solidifies at 157.36 ºC to a white crystalline substance with a face-centered cubic structure. It is slightly soluble in water.
Krypton is an inert gas element. Its closed-shell, stable octet electron configuration allows zero reactivity with practically any substance. Only a few types of compounds, complexes and clathrates have been synthesized, mostly with fluorine, the most electronegative element.
The commercial applications of krypton are fewer than those of helium or argon. Its principal use is in fluorescent lights. It is mixed with argon as a filling gas to enhance brightness in fluorescent tubes. Other applications are in flash tubes for high-speed photography and incandescent bulbs. Radioactive Krypton-85 is used as a tracer to monitor surface reactions. The unit of length “meter” was once defined in terms of the orange-red spectral line of Krypton-86.
Properties of Krypton
| Name | Krypton |
| Symbol | Kr |
| Atomic number | 36 |
| Atomic weight | 83.30 |
| Standard state | Gas at 298 °K |
| CAS Registry ID | 7439-90-9 |
| Group in periodic table | 18 |
| Group name | Noble gas |
| Period in periodic table | 4 |
| Block in periodic table | p-block |
| Color | Colorless |
| Classification | Nonmetallic |
| Melting point | -157.36 °C |
| Boiling point | -153.22 °C |
| Thermal conductivity | 0.00943 W/(m·K) |
| Electronegativity | 3.00 |
| Heat of vaporization | 9.02 kJ·mol-1 |
| Heat of fusion | 1.64 kJ·mol-1 |
| Density of gas | .0037 g/cm3 |
| Density of liquid | No data available |
| Density of solid | 2.16 g/cm3 |
| Electron configuration | [Ar]3d104s24p6 |
| First ionization potential | 13.999 volts |
| Oxidation state | 0 (an uncommon oxidation state +2 exists for its difluoride) |
| Critical temperature | -63.7 ºC |
| Critical pressure | 54.30 atm |
| Critical density | 0.908 g/L |
