In 1803, the young English chemist John Dalton affirmed that atoms were the smallest unit of matter and he was the first to propose an atomic model. Although his atomic model was not precise, it interested other scientists in his studies. Ultimately, the combined research and experiments of Democritus, John Dalton, JJ Thomson, Ernest Rutherford, and Niels Bohr developed the atomic model we know today, a positively charged nucleus surrounded by orbitals with scattered electrons. This important discovery led to the development of many new areas of knowledge. One of the most important areas was the introduction to nuclear medicine. Nuclear medicine is a branch of medicine that involves the use of radioactive isotopes and imaging. (Tangient LLC) This branch of medicine was made possible through the combined research of Antoine Henri Becquerel, Marie and Pierre Curie, and Ernest Rutherford. Becquerel experimented with a crystal containing uranium by placing it on a photographic plate placed in a dark drawer and trying to test its reactions to energy from the sun. However, this crystal was emitting its own rays even without the initiating energy source and although he did not know it himself, what he discovered was radioactivity. (Slowiczek) Even though he didn't do further research into why his experiment went the way it did, Marie Curie and Pierre Curie were there to continue what he had started. After hearing about what Becquerel had accomplished, they got their own crystals to test things out for themselves. They experimented with two types of uranium, one containing ore and the other containing pure uranium. From these experiments, they were the first to identify the emissions as “radioactivity”. In addition, they disk...... middle of paper ......or Medical Isotopes. “Frequently Asked Questions”. Medical isotopes. Citizens for Medical Isotopes, 2009. Web. January 8, 2014. .• Mortenson, Jann. “Medical use of radioactive isotopes.” March 11, 2013. PDF file. • ProScan Imaging. “RADIOLOGY: BASIC MODALITIES.” Ed. Resham R. Mendi, Stephen J. Pomeranz, and Rod Willis. October 2007. PDF file. • Slowiczek, Fran and Pamela M. Peters M. Peters. “The discovery of radioactivity: the dawn of the nuclear age. » Access excellence. Access Excellence at the National Museum of Health, 1994. Web. January 8, 2014. .• Tangient LLC. “Nuclear Medicine”. Wikispaces. Tangient LLC, 2014. Web. 8 January 2014. • WHO Media Centre. “Noncommunicable diseases.” World Health Organization. WHO, 2014. Web. January 9. 2014. .