An atomic mass of 54.94u suggests that the element is potassium (K). Potassium has three naturally occurring isotopes: potassium-39 (39K), potassium-40 (40K), and potassium-41 (41K).
The isotopic abundances of these isotopes are approximately 93.26% for 39K, 0.012% for 40K, and 6.73% for 41K. The atomic mass of an element is calculated by taking into account the mass of each isotope and its relative abundance. Therefore, the presence of multiple isotopes contributes to the overall atomic mass of an element.
Given that potassium has multiple isotopes and the atomic mass of potassium is 54.94u, it is evident that there are different isotopes of potassium. The relative abundances of these isotopes contribute to the overall atomic mass of the element.