1875+-+1900

** __Henri Becquerel__ ** -Died in Le Croisic, France on August 25 1908.
 * __ 1875 - 1900 __ **
 * -Born in Paris, France on December 15, 1852.

Henri Becquerel was a French physicist born into a scientific family extending through several generations. The most famous of all is his grandfather Antoine-Cesar Becquerel. He received his formal scientific education at the École Polytechnique and training on engineering at the École des Ponts et Chaussées. Besides his teaching and research posts, Henri was appointed chief engineer in the Department of Bridges and Highways for many years. His research concerned electricity, energy, optical phenomena, and magnetism since these were major areas of study during the 19th century. Many years his main focus was the rotation of plane-polarized light by magnetic fields and then it was followed by infrared radiation. He examined the spectra of different phosphorescent crystals under infrared stimulation. Becquerel extended the research of his father by studying the similarity between absorption of light and emission of phosphorescence in some uranium compounds. Henri Becquerel was an accomplished and respected physicist by 1896.

Antoine Henri Becquerel made an accidental discovery. While he was studying the capability of uranium salts that had been exposed to sunbeams to fog photographic film plates. Since there were bad weather conditions, he could not expose the sample to sunlight. However, he accidentally left it on top of the photographic plate. When he developed the plate, he found out that the uranium salt still fogged the plate. Therefore, he proved his point that something that was very alike to X rays was released by luminescent substance at the same time it threw off visible radiation. His works awaken the world for the discovery of new radioactive materials. In addition, Henri made three other significant contributions. The first was to measure the deflection of beta particles. From the charge to mass value he got, he demonstrated that the beta particles were the same as Joseph Thomson’s newly identified electron. One more discovery was the condition that the supposedly active substance in uranium, uranium X, vanish its radiating capability. ** 
 * __Wilhelm C. Roentgen__

- Date of Birth: March 27, 1845 - Date of Death: Feb. 10, 1923 - Country of Origin: Germany Wilhelm Roentgen showed a love for nature and a great ability for mechanics since an early age. He went to Utrecht University to study physics, then got out and entered The Zurich Polytechnic to study mechanical engineering. After graduating, he spent 5 years as an assistant, 2 years as a university teacher and then climbed to be the chair of physics in the University of Giessen. In 1870 he started publishing his scientific works and by 1896, he had invented the X-ray.For this he won a lot of fame and money yet he stayed an honest, calm, modest man. He also kept his like for the outdoors and he was constantly in trips. In 1872, he married Ana Bertha Ludwig. Four years after she died, Roentgen died in 1923. On November 8, 1895, Roentgen discovered the X-ray. It was created by the passing of an electric current through a gas of extremely low pressure. This had been donde before by other scientists yet not until Roentgen tried it, none had made the cathode ray work in a dark room, where no light hit the discharged tube.Roentgen found that by interposing objects like his wife's hand and imbolizing them, he could see the 1st X-ray as we know it today. This discovery helped the atomic theory because with it, it was possible to research more about the structure of objects and the structure of elements.

__JJ Thomson__ ** **-Born in Cheetham Hill, a suburb of Manchester, England on December 18, 1856. -Died in Cambridge, UK on August 30, 1940. JJ Thomson’s father was a bookseller and therefore he did not have the fee for his apprenticeship. However, he wanted his son to be an engineer. Thomson entered Owens College. His professor of mathematics noticed his extraordinary intelligence and motivated him to apply for a scholarship at Trinity College in Cambridge. He was a student who finished the third year of math with first-class honors. JJ Thomson became Cavendish Professor of Physics in 1884. His discovery began one year later in the Cavendish laboratory where he conducted a series of experiments. The English physicist, JJ Thomson discovered the electron in 1897. “Electrons are negatively charged subatomic particles.” He performed many experiments that involved passing electric current at a low pressure through gases. In glass tubes, he sealed the gases and at both ends the tubes were fitted with metal disks called electrodes. These electrodes were attached to a source of electricity. There were two electrons. The anode became positively charged and the other one, the cathode, became negatively charged. The outcome was a glowing beam or cathode ray that traveled from the cathode to the anode. His investigations into the action of electrostatic and magnetic fields would later result in the invention of the mass spectrometer. **


 * __Plum Pudding Model__ **

**This model was proposed by JJ Thomson, the English physicist who discovered the electron. The plum pudding model is also known as the Chocolate Chip Cookie or the Blueberry Muffin Model. The “pudding” is positively charged and the plums dotting the dough are negatively charged electrons. This model has a dispersed positive charge in comparison to today’s atom which has a very small and dense positively charged nucleus. Therefore, this model of the atom was only successful to explain why most atoms were neutral. The Plum Pudding model was visualized as having a cloud of positive charge in contrast to the recent atomic model which illustrates a positive nucleus surrounded by an electron cloud. **