Question

238u undergoes radioactive decay to 234th. how many protons, electrons, and neutrons are gained or lost by the 238u atom during this process?

Answer 1

U^235Number of protons = 92 pNumber of electrons = 92 eNumber of neutrons = 235 – 92 = 143n
U^238Number of protons = 92pNumber of electrons = 92eNumber of neutrons = 238 – 92 = 146n
Electron configuration of U atom U = 92 U = [Rn] 5f^6 6d^0 7s^0 U = [Rn] 5f^36d^17s^2, 7s is completely filled and others are less than half filled. 
(_92^238)U  Decays to (_90^234)ThIt loses 2 protons, 2 electrons and loses 2 neutrons Th = [Rn] 6d^2 7s^2 There is no electron in 5f subshell and 6d contains 2e^-, 7s completely filled