who discovered this decay?
Ernest Rutherford, Frederick Soddy
History of discovery
Further research by Becquerel, Ernest Rutherford, Paul Villard, Pierre Curie, Marie Curie, and others showed that this form of radioactivity was significantly more complicated. Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula. Rutherford and his student Frederick Soddy were the first to realize that many decay processes resulted in the transmutation of one element to another. Subsequently, the radioactive displacement law of Fajans and Soddy was formulated to describe the products of alpha and beta decay.
who was lise meitner? She was an Austrian-Swedish physicist. in which country did she live in her early days? In the Leopoldstadt district of Vienna any particular educational institution that she attended as a student? University of Vienna why did she have to flee from germany? Because she lost her Austrian citizenship. why? UNANSWERABLE can you mention any of her contributions? She completed the work on beta ray spectrum that she had begun with Hahn and Baeyer, and also her own study of the uranium decay chain. could you please elaborate the last reaction? It refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations - a.k.a. "radioactive cascade". can you mention any health hazard caused by this decay? The dangers are not immediately recognized.
Ernest Rutherford and his student Frederick Soddy Henri Becquerel UNANSWERABLE
Radioactive decay Radioactive decay
History of discovery History of discovery
Further research by Becquerel, Ernest Rutherford, Paul Villard, Pierre Curie, Marie Curie, and others showed that this form of radioactivity was significantly more complicated. Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula. Rutherford and his student Frederick Soddy were the first to realize that many decay processes resulted in the transmutation of one element to another. Radioactivity was discovered in 1896 by the French scientist Henri Becquerel, while working with phosphorescent materials. 
wiki:13605792
Radioactive decay [SEP] History of discovery
It became clear from these experiments that there was a form of invisible radiation that could pass through paper and was causing the plate to react as if exposed to light. At first, it seemed as though the new radiation was similar to the then recently discovered X-rays. Further research by Becquerel, Ernest Rutherford, Paul Villard, Pierre Curie, Marie Curie, and others showed that this form of radioactivity was significantly more complicated. Rutherford was the first to realize that all such elements decay in accordance with the same mathematical exponential formula. Rutherford and his student Frederick Soddy were the first to realize that many decay processes resulted in the transmutation of one element to another.