PDF Loss of a - Fort Bend ISD • Nuclear reactions can change one element into another element 226Ra 88 222Rn 86 4 He 2 + Atomic number: 88 = 86 + 2 Mass number: 226 = 222 + 4 BALANCING A balanced nuclear reaction conserves the mass and atomic (proton) numbers. In other words, these values must be identical on both sides of the reaction X X = element symbol Z = atomic number