Uranium-238 decays into thorium-234.
How do scientists explain why this happens?
A) The nucleus is unstable.
B) The atom is unstable.
C) It is bombarded by alpha particles.
D) It is bombarded by neutrons.
A) The nucleus is unstable.
In this case, the uranium-238 nucleus is unstable and undergoes radioactive decay to become a more stable thorium-234 nucleus. This process helps to explain why uranium-238 decays into thorium-234.