(Incomplete)
| Isotope | Abundance | T½ (s) | Decay |
| 31K | | | |
| 33K | | | |
| 34K | | | |
| 35K | | | |
| 36K | | | |
| 37K | | | |
| 38K | | | |
| 39K | 93.2581 % | Stable | - |
| 40K | | | |
| 41K | 6.7302 % | Stable | - |
| 42K | | | |
| 43K | | | |
| 44K | | | |
| 45K | | | |
| 46K | | | |
| 47K | | | |
| 48K | | | |
| 49K | | | |
| 50K | | | |
| 51K | | | |
| 52K | | | |
| 53K | | | |
| 54K | | | |
| 55K | | | |
| 56K | | | |
Note: No 32K isotope.
All data from [8].
| α: | alpha particle emission (4He nucleus) |
| β+: | emission of an anti-electron and a neutrino. A proton inside the nucleus is transformed into a neutron |
| β-: | emission of an electron and an anti-neutrino. A neutron inside the nucleus is transformed into a proton |
| ec: | electron capture: capture of one orbital electron by the the nucleus. A proton inside the nucleus is transformed into a neutron plus a neutrino |
| SF: | Spontaneous Fission: a nucleus spontaneously splits into fragment nuclides |
| IT: | Isomeric Transition: a level above the ground state decays via electromagnetic process |
| n: | neutron emission |
| p: | proton emission |
| β- n (and similar): | beta- decay followed by delayed neutron emission |
| 