78 neutrons Click to see full answer. Keeping this in view, how many neutrons does cesium 132 have? Name Cesium Atomic Mass 132.9054519 atomic mass units Number of Protons 55 Number of Neutrons 78 Number of Electrons 55 Subsequently, question is, what is cesium found in? 1860 Also to know, how many isotopes does cesium have? Isotopes of caesium. Caesium (55Cs) has 40 known isotopes, making it, along with barium and mercury, one of the elements with the most isotopes. The atomic masses of these isotopes range from 112 to 151. Only one isotope, 133Cs, is stable.How many neutrons does potassium have?For potassium it is about 39. This means that the atomic weight is 39 for both protons and neutrons. Since we know that the number of protons is 19 we can calculate the number of neutrons (39 19) as 20.