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What is Matter? Matter is anything that has mass. All objects are made of matter. Air, water, a brick, even you are made of matter! States of matter Atomic particles and isotopes VIDEO-Clip: http://www.britannica.com/EBchecked/topic/41549/atom Subatomic particles Particles smaller than an atom. They may be elementary or composite. Electrons (elementary) Protons (composite), made of 3 quarks Neutrons (composite), made of 3 quarks John DALTON Over eighty years ago, scientists thought that the atom was the smallest piece of matter. Atom: the building block of matter Solid sphere model John DALTON (1844) http://www.etownschools.org/Page/3502 John DALTON’s atomic theory VIDEO CLIP: http://www.britannica.com/EBchecked/topic/41549/atom John THOMSON discovered the electrons 1940 John Thomson 1906 Nobel Prize in Physics Thomson at work The Cavendish Laboratory, Cambridge (UK) What could these rays be? A simple cathode ray tube. VIDEO (3:46’) http://www.youtube.com/watch?v=4QAzu6fe8rE Do atoms have parts? JJ Thomson suggested that they do! He advanced the idea that cathode rays are really streams of very small pieces of atoms. "We have in the cathode rays matter in a new state." J.J. Thomson experimenting J.J. Thomson Talks About the Size of the Electron To listen to J.J. Thomson speaking on his discovery: AUDIO: http://www.aip.org/history/electron/jjsound.htm "Could anything at first sight seem more impractical than a body (the electron) which is so small that its mass is an insignificant fraction of the mass of an atom of hydrogen? --which itself is so small that a crowd of these atoms equal in number to the population of the whole world would be too small to have been detected by any means then known to science." Recording made in 1934. From the soundtrack of the film, Atomic Physics copyright © J. Arthur Rank Organization, Ltd., 1948. John THOMSON’s model of the atom Raisin cake model J.J. Thomson theorized that electrons were surrounded by a positively charged material, uniformly distributed. Ernest Rutherford discovered the nucleus 1937 Ernest Rutherford 1908 Nobel Prize Solar system model Rutherford’s experiment The gold-foil experiment Alpha particle: helium nucleus (4u2+) VIDEO: http://www.youtube.com/watch?v=Zd6_zVdMgJk Expected results according to….. Thomson’s model Rutherford’s model Rutherford’s model of the atom Rutherford envisioned the atom as a miniature solar system, with electrons orbiting around a massive nucleus. Solar system model What is Matter? neutrons mesons Quarks and gluons Do you think that the quark is the smallest piece of matter or do you think that there might be something smaller inside the quark? You name it! You name it! The model of atom created by Rutherford shouldn’t exist! According to classical physics, an electron in orbit around an atomic nucleus should emit electromagnetic radiation (photons) continuously. The resulting loss of energy implies that the electron should spiral into the nucleus in a very short time (atoms cannot exist!!) Niels BOHR 1962 Niels BOHR 1922 Nobel Prize Quantized shell model Fixed orbits In 1913 Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus. Bohr proposed that electrons are restricted to certain fixed (quantized) orbits. An electron can jump between these orbits by absorbing or emitting a photon with the appropriate precise wavelenght. quantized shell model Shell model of the atom Bohr's idea was that each discrete orbit could only hold a certain number of electrons. After that orbit is full, the next level would have to be used. This gives the atom a shell structure, in which each shell corresponds to a Bohr orbit VIDEO: http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model For working hard with me! Electronic configuration of different atoms VIDEO: http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model Nuclear fission VIDEO: http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model Atomic bonds VIDEO: http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model Nuclear power VIDEO: http://www.britannica.com/EBchecked/topic/41549/atom/48360/Bohrsshell-model