The key problem underlying the discovery of radium was:
A) Why certain isotopes of thorium are radioactive.
B) Why uranium has the power to darken photographic plates.
C) Why pitchblende emits rays that are stronger than rays emitted by pure uranium.
D) Why rays emitted by thorium are stronger than rays emitted by uranium.
E) Why X-rays are stronger than rays emitted by pure uranium.

Question

Quizplus · Accepted Answer

The key problem underlying the discovery of radium was why pitchblende emits rays that are stronger than rays emitted by pure uranium. This led Marie and Pierre Curie to hypothesize that there must be another element present in pitchblende that was more radioactive than uranium, which they later discovered to be radium.

The Key Problem Underlying the Discovery of Radium Was