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Radioactivity

 

 

Marie and Pierre Curie

 

ð Discovered two previously unknown elements in 1906 that are highly radioactive - they were named radium and polonium

 

ð The phenomenon was impervious to physical and chemical treatments.

 

ð The cause, therefore, was reasoned to be deep within the atom - the nucleus

 

ð Radioactivity was determined to be caused by the disintegration of an unstable nucleus 

  

 

Radiation Types

 

ð The Radioactive rays were observed to be of three types:

         Ø Alpha rays, which could barely penetrate a piece of paper

        Ø Beta rays, which could penetrate 3 mm of aluminum

        Ø Gamma rays, which could penetrate several centimeters of lead

 

ð Alpha and beta rays are bent in opposite directions in a magnetic field, while gamma rays are not bent at all.

 

ð We now know that alpha rays are helium nuclei, beta rays are electrons, and gamma rays are electromagnetic radiation.