In 1913, an element was known to "emanate" from radium-226 by alpha emission and then to decay to polonium-218, also by $\alpha$ emission. What was the unknown element?

Question

Quizplus · Accepted Answer

The element that "emanates" from radium-226 by alpha emission is radon-222, which then decays to polonium-218 by alpha emission (F1F1F1S1αF1F1F10 emission). This is a well-known decay pathway of radium-226, and the only element that fits this description is radon-222.

In 1913, an Element Was Known to "Emanate" from Radium-226 α\alphaα

In 1913, an Element Was Known to "Emanate" from Radium-226 $\alpha$