Becquerel In 1896, Becquerel's earlier work was surpassed by his discovery of the occurrence of natural radioactivity. Becquerel decided to investigate whether there was any connection between X-rays and naturally occurring phosphorescence, after his discussion with Henri Poincaré on the radiation which had been recently discovered by Röntgen (X-rays) and which was accompanied by a type of phosphorescence in the vacuum tube. He had inherited from his father a supply of uranium salts, which exhibits …showed first 75 words of 323 total…

…showed last 75 words of 323 total…fired a 15-inch naval shell at a piece of tissue paper and the shell came right back and hit you." From this straightforward observation, Rutherford concluded that the atom's mass must be concentrated in a tiny, positively-charged nucleus, while the electrons occupy the farthest ranges of the atom. Although this planetary model of the atom has been greatly sophisticated over the years, it remains as legitimate today as when it was originally devised by Rutherford.