Kaplan MCAT Sample Question


A nuclide undergoes 2 alpha decays, 2 positron decays, and 2 gamma decays. What is the difference between the atomic number of the parent nuclide and the atomic number of the daughter nuclide?

  1. 0
  2. 2
  3. 4
  4. 6

The answer is:

D. 6

In Alpha decay, an element loses two protons and two neutrons. In positron decay, a proton is converted into a neutron. Gamma decay, meanwhile, has no impact on the atomic number of the nuclide. Therefore, two alpha decays and two positron decays will yield a daughter nuclide with 6 fewer protons than the parent.

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