Element: Krypton
General data
| Element name | Krypton |
|---|---|
| Chemical symbol | Kr |
| Atomic number Z | 36 |
| Year discovered | 1898 |
| Standard state (25°C) | Gas |
| Category | Noble gas |
| Block | p |
| Atomic mass | 83.798 |
| CPK color | #5CB8D1 |
Physical properties
| Melting point | 115.79 K (-157.36 °C) |
|---|---|
| Boiling point | 119.93 K (-153.22 °C) |
| Density | 0.003733 g/cm³ |
Energy properties
| First ionization energy | 14 eV |
|---|---|
| Electron affinity | no data |
Atomic structure
| Protons | 36 (Atomic number) |
|---|---|
| Neutrons (Kr-84, most abundant isotope) | 48 |
| Electrons | 36 |
| Electron configuration | [Ar] 4s² 3d¹⁰ 4p⁶ |
| Oxidation states | no data |
| Electronegativity (Pauling) | 3 |
| Atomic radius (van der Waals) | 202 pm |
Ionization energies - NIST ASD (36 states)
| State | Charge | Ioniz. energy (eV) | Type |
|---|---|---|---|
| Kr I | 0+ | 13.9996055 ± 0.000002 | measured |
| Kr II | 1+ | 24.35984 ± 0.00012 | measured |
| Kr III | 2+ | 35.838 ± 0.02 | measured |
| Kr IV | 3+ | 50.85 ± 0.11 | measured |
| Kr V | 4+ | 64.69 ± 0.2 | semi-empirical |
| Kr VI | 5+ | 78.49 ± 0.2 | semi-empirical |
| Kr VII | 6+ | 109.13 ± 0.05 | calculated |
| Kr VIII | 7+ | 125.802 ± 0.003 | measured |
| Kr IX | 8+ | 233 ± 0.7 | semi-empirical |
| Kr X | 9+ | 268 ± 3 | calculated |
| Kr XI | 10+ | 308 ± 3 | calculated |
| Kr XII | 11+ | 350 ± 3 | calculated |
| Kr XIII | 12+ | 391 ± 4 | calculated |
| Kr XIV | 13+ | 446 ± 3 | calculated |
| Kr XV | 14+ | 492 ± 5 | calculated |
| Kr XVI | 15+ | 540 ± 3 | calculated |
| Kr XVII | 16+ | 591 ± 3 | calculated |
| Kr XVIII | 17+ | 640 ± 3 | calculated |
| Kr XIX | 18+ | 785.316 ± 0.012 | semi-empirical |
| Kr XX | 19+ | 831.6 ± 0.9 | semi-empirical |
| Kr XXI | 20+ | 882.8 ± 1.3 | semi-empirical |
| Kr XXII | 21+ | 945 ± 3 | semi-empirical |
| Kr XXIII | 22+ | 999 ± 2.4 | semi-empirical |
| Kr XXIV | 23+ | 1042 ± 5 | semi-empirical |
| Kr XXV | 24+ | 1155 ± 1.6 | semi-empirical |
| Kr XXVI | 25+ | 1205.23 ± 0.04 | semi-empirical |
| Kr XXVII | 26+ | 2928.9 ± 1.7 | semi-empirical |
| Kr XXVIII | 27+ | 3072 ± 5 | semi-empirical |
| Kr XXIX | 28+ | 3228 ± 7 | semi-empirical |
| Kr XXX | 29+ | 3380 ± 30 | semi-empirical |
| Kr XXXI | 30+ | 3584 ± 4 | semi-empirical |
| Kr XXXII | 31+ | 3752 ± 2.5 | semi-empirical |
| Kr XXXIII | 32+ | 3971 ± 4 | semi-empirical |
| Kr XXXIV | 33+ | 4109.083 ± 0.009 | calculated |
| Kr XXXV | 34+ | 17296.424 ± 0.004 | calculated |
| Kr XXXVI | 35+ | 17936.2405 ± 0.0016 | calculated |
Value type as given by NIST ASD: measured - from evaluated experimental data; calculated - from ab initio calculations (mostly highly ionised atoms that have not been measured; for the simplest ones, e.g. H I, the calculation is more accurate than measurement); semi-empirical - from interpolation, extrapolation or another semi-empirical method.
Photos
Isotopes (36)
| A | N | Half-life | Decay |
|---|---|---|---|
| Kr-67 | 31 | 7 ms | 2p |
| Kr-68 | 32 | 22 ms | EC/β⁺ |
| Kr-69 | 33 | 27.9 ms | EC/β⁺ |
| Kr-70 | 34 | 45.19 ms | EC/β⁺ |
| Kr-71 | 35 | 95.0 ms | EC/β⁺ |
| Kr-72 | 36 | 17.1 s | EC/β⁺ |
| Kr-73 | 37 | 27.3 s | EC/β⁺ |
| Kr-74 | 38 | 11.50 min | EC/β⁺ |
| Kr-75 | 39 | 4.55 min | EC/β⁺ |
| Kr-76 | 40 | 14.8 h | EC/β⁺ |
| Kr-77 | 41 | 71.3 min | EC/β⁺ |
| Kr-78 | 42 | stable | - |
| Kr-79 | 43 | 34.96 h | EC/β⁺ |
| Kr-80 | 44 | stable | - |
| Kr-81 | 45 | 2.29×10⁵ a | EC |
| Kr-82 | 46 | stable | - |
| Kr-83 | 47 | stable | - |
| Kr-84 | 48 | stable | - |
| Kr-85 | 49 | 10.735 a | β⁻ |
| Kr-86 | 50 | stable | - |
| Kr-87 | 51 | 76.1 min | β⁻ |
| Kr-88 | 52 | 2.803 h | β⁻ |
| Kr-89 | 53 | 3.15 min | β⁻ |
| Kr-90 | 54 | 32.32 s | β⁻ |
| Kr-91 | 55 | 8.57 s | β⁻ |
| Kr-92 | 56 | 1.841 s | β⁻ |
| Kr-93 | 57 | 1.284 s | β⁻ |
| Kr-94 | 58 | 212 ms | β⁻ |
| Kr-95 | 59 | 114 ms | β⁻ |
| Kr-96 | 60 | 80 ms | β⁻ |
| Kr-97 | 61 | 62 ms | β⁻ |
| Kr-98 | 62 | 43 ms | β⁻ |
| Kr-99 | 63 | 10 ms | β⁻ |
| Kr-100 | 64 | 7 ms | β⁻ |
| Kr-101 | 65 | unknown | β⁻ |
| Kr-102 | 66 | unknown | β⁻ |
Data sources
- PubChem Periodic Table API - Retrieved on 29 June 2026 - licence: CC0
- IUPAC CIAAW - Abridged Standard Atomic Weights 2024 - Table version: 2024 - licence: Public domain
- NNDC Wallet Cards 2023 - Data as of 15 October 2024 - licence: Public domain
- NIST Atomic Spectra Database (ASD) - Retrieved on 29 June 2026 - licence: © U.S. Secretary of Commerce
- Images of Elements - Retrieved on 29 June 2026 - licence: CC BY 3.0