Potassium-40 (K40) is the most abundant isotope of potassium, followed by potassium-39 (K39) and then potassium-41 (K41).
The main isotopes of potassium are potassium-39, potassium-40, and potassium-41. Other isotopes of potassium include potassium-42, potassium-43, potassium-44, potassium-45, potassium-46, potassium-47, potassium-48, potassium-49, potassium-50, potassium-51, potassium-52, potassium-53, potassium-54, and potassium-55.