Let's suppose that a massive element has undergone a radioactive decay. The new element has the same mass but the atomic number decreased by one. What other particle was emitted in this decay? A) Alpha partice B) Positron C) Electron E) Gamma Ray Case #2 What if the atomic number and mass number stayed the same? Case #3 What if the atomic number increased by one and the mass number stayed the same? Good Luck on the MCAT. I'll be later in the week.