Answer :
Final answer:
Cesium with atomic number 55 and mass number 137 is known as Cesium-137 (137Cs), a radiogenic isotope produced from nuclear fission.
Explanation:
The element Cesium (Cs) with atomic number 55 and mass number 137 is known as Cesium-137 (137Cs). This designation indicates that the isotope of cesium has 137 nucleons (protons and neutrons) in its nucleus. With cesium having an atomic number of 55, it also means this isotope has 55 protons and 137 - 55 = 82 neutrons. Cesium-137 is a radiogenic isotope produced from nuclear fission, found in the aftermath of nuclear weapons tests and nuclear accidents, such as the Chernobyl disaster.
