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| Ernest Rutherford's Work |
| The Atom By 1911 all of the components of the atom had been discovered, protons, neutrons and electrons. What remained unclear was how the protons and electrons were arranged and what their path of movement within the atom was. J.J. Thomson introduced the Plum Pudding model. In this model electrons and protons were mixed throughout the atom. Rutherford was skeptical of J.J. Thomson's theory, and decided to test the Plum Pudding model. Rutherford devised the Gold Foil experiment, he stated that is Thomson's model was correct then the mass of the atom was spread out throughout the entire atom. In the experiment he shot alpha particles (consisting of protons and neutrons) moving at high speeds towards a gold sheet. He detected what happened to these atoms after they hit the gold with a sheet of glow in the dark material. When an alpha particle hit the glow in the dark sheet it made a bright light where it struck. Most of the alpha particles passed right through the gold atoms. This meant most of the atom was empty space. The empty space was te space between the nucleus and the electrons. Some of the alpha particles were deflected slightly this was due to their attraction to the passing electrons moving around the outside of the atoms. A small percentage shot straight back, this was because thy struck the nucleus and were sent straight back. All of these observations contributed to Rutherford's model of the atom. In the center there is a positively charged nucleus made of protons and neutrons, and the negatively charged electrons orbit the nucleus much like planets orbit the sun. |
| The Proton In yet another one of Rutherford's experiments, he managed to produce the disintegration of a non-radioactive atom. By dislodging a single particle, he found that it had a positive charge. He concluded that since it was positive it much have come from the nucleus. He called this new particle a proton. |
| Two Kinds of Radiation Rutherford also discovered that there are two types of radiation, alpha and beta. By stacking aluminum foil sheets, he found that the intensity of radiation decreases with the thickness of the foil that is penetrated. He also found that after a certain thickness, the radiation passing though was low but it did not then decrease with increasing thickness of the foil. From this he concluded that the radiation consisted of two compnents; alpha rays, which were intense and quickly absorbed, and beta rays which were less intense, but penetrated further. Alpha radiation can be stopped by a sheet of paper and cannot penetrate the skin. Beta radiation is slightly stronger and can go on through an inch of water or skin but it cannot go through a sheet of thick aluminum foil. Gamma radiation is the strongest of these three types of radiation, it can penetrate the human body. Lead or thick concrete are the only things that can stop gamma rays. |
| Radioactive Half-Life Working with Frederick Soddy in 1902, Rutherford found that radioactive material disintegrates. Each element has a characteristic lifetime of which is indicated by the time that it takes for its intensity to decrease by half, therefore being declared Radioactive Half-life. Rutherford's formulation of radioactivity is still accepted to this fay. An explanation of radioactivity: each decay of the atoms of radioactive materials signifies the transmutation of a parent elements into a daughter (nuclide formed after decay of a radioactive element) with each type of atom having its own transformation period otherwise known as half-life. Rutherford was awarded the 1908 Nobel Prize for chemistry, for his work on radioactivity. |
| Daughter Atom Rutherford also discovered the daughter atom. Is is a nuclide formed after radioactive decay. |