GENERAL KNOWLEDGE

Detailed explanation-1: -After Marie and Pierre Curie first discovered the radioactive elements polonium and radium, Marie continued to investigate their properties. In 1910 she successfully produced radium as a pure metal, which proved the new element’s existence beyond a doubt.

Detailed explanation-2: -Then Curie discovered an even more radioactive element, radium, and, through observation of radium, made a fundamental discovery: Radiation wasn’t dependent on the organisation of atoms at the molecular level; something was happening inside the atom itself.