Nuclear Energy Short history 1930, atom made up of neutrons and protons 1.67X10-27kg 1840 times heavier than electron A Z N Mass Atomic(proton) Number of number number neutrons ME=Am.c2 复旦大学环境科学与工程系 Department of Environmental Science and Engineering, Fudan UniversityNuclear Energy Short History 1930, atom made up of neutrons and protons. 1.67×10-27 kg 1840 times heavier than electron A = Z + N Mass number Atomic (proton) number Number of neutrons ∆E=∆m·c2