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Cathode ray tube
Scientists developed the cathode ray tube. They discovered that when most of air inside a glass tube was removed by a vaccum and applied a high voltage to two electroedes inside the tube that a small electric current would pass through the remaining gas. At that time they believed that all gases were insulators. -
X-rays discovered
Wilhelm Rontgen discovers X-rays in 1895. He was experimenting the secondary emissions caused by cathode rays . He put thick black paper over the cathode tube to ovserve the emissions oustide the tuve as the rays struck a metal plate. Wilhelm Rontgen saw that outside the tube the rays caused fluorescent mineral to glow which exposed photographic film. -
Radioactivity
Henri Becquerel discovered natural raido activity when a photographic plate that was covered darkened by a mineral that contained uranium. This radiation was different then Wilhelm Rontgens X-ray radiation. -
Marie and Pierre Curie
Marie Curie and her husband Pierre Curie stared to wonder what caused uranium to produc Becquerel rays, so they started to analyze uranium. Marie Curie investigated other elements to see if they gave off Becquerel rays. She discovered that thorium gave off a similar emission. As they kept on studying they discovered two new elements, radium and polonium. -
The Concept of the Nucleus was Proposed
Ernest Rutherford a phycisist from New Zealand, used radioacitity to explore the atom. He discovered that most of the particels went through the foil, some particles were deflected and some other particles bounced back from the foil. Ernest Rutherford came to the conclusion that an atom is mostly empty space and that the positive charged particles and all the mass of an atom is at the center. This part came to be the nucleus. -
Existance of Neutrons
A British physicist names James Chadwick found that atomic nuclei have a particle in them that has a neutral charge, he called this a neutron. A neutron has the same mass as a proton and because it has no charge, it was difficult to find.
