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Dear students ,

Dear students , How are you, we hope that you all are fine especially after this long . long vacation. It is time to work , we try always to offer you the best. Now hoping that you too will do your best to pass this critical period of time & to complete together our success.

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  1. Dear students, How are you, we hope that you all are fine especially after this long .long vacation. It is time to work , we try always to offer you the best. Now hoping that you too will do your best to pass this critical period of time & to complete together our success. For better future to our country. Science Department

  2. Chapter one Atomic structure Ch. Ahmed elfekey

  3. Lesson one

  4. Models of the Atom a Historical Perspective

  5. 1- Greek philosophers Substances consists of smaller particles which are indivisible called A toms A = no tom = divide

  6. fire Dust air water Aristotle Aristotle He rejected the concept of atom ** He said that ** Matter consists of 4 main components which are .

  7. It was believed that cheap metal as Ironor Copper Can be changed into precious ones as gold by change the ratio of constituent

  8. 3- Boyle He refused Aristotle's idea & givethe 1st definition of theelement Element Simple pure substance that can not be changed into simpler form by traditional chemical method

  9. Who’s Next? Late 1700’s - John Dalton- England. Teacher- summarized results of his experiments and those of others. Elements substances that can’t be broken down In Dalton’s Atomic Theory Combined idea of elements with that of atoms.

  10. Dalton’s Atomic Theory a- The matter is composed of very minute particles which is named atoms b- The atom is solid undivided particle c- The atoms of each element are different from the atoms of any other element

  11. 5 – Thomson Gases do not conduct electricity under normal conditions of pressure & temperature

  12. The condition at which the gas could be conduct electricity Discharge tube with a- Pressure ranges between 0.01 – 0.001 mm Hg b- Potential difference of about 10,000 volts was applied through the space between the Cathode rays are the carriers of electric current from cathode to anode inside a vacuumed tube

  13. Voltage source Thomson’s Experiment - + Metal Disks

  14. Voltage source Thomson’s Experiment - + • Passing an electric current makes a beam appear to move from the negative to the positive end

  15. Voltage source Thomson’s Experiment + - • By adding an electric field he found that the moving pieces were negative • By adding an electric field

  16. G.R.F To get the cathode rays, the used tube is discharged to a very low pressure. Because gases do not conduct electricity Under normal pressure

  17. Cathode rays A stream of electrons produced at the ( -ve ) electrode ( cathode ) of the vacuum glass tube containing a gas at low pressure

  18. Properties of cathode rays 1-A stream of electrons produced at the ( -ve ) electrode ( cathode ) of the vacuum glass tube containing a gas at low pressure • 2-It moves in straight lines. • 3-They have thermal effect. • 4-They are affected by both electric & magnetic fields Chemist . Ahmed elfekey

  19. Voltage source 5-They are negatively charged. + - • 6-They do not differ either in behavior or in nature • if the material of cathode or the used gas are changed • [ Fundamental constituent of any matter ]

  20. Cathode Ray Tube (Michael Faraday (1791-1867))

  21. Thomson’s Model A sphere of a uniform (+ve) electricity in which a number of (-ve) charged electrons are embedded in to make the atom electrically neutral

  22. Rutherford's atom

  23. Rutherford’s Experiment Ernest Rutherford English physicist. (1910) Believed the plum pudding model of the atom was correct. Wanted to see how big they are. Used radioactivity. Alpha particles - positively charged pieces given off by uranium. Shot them at gold foil which can be made a few atoms thick.

  24. Rutherford, Geiger, and Marsden(Early 20th Century) Positively charged alpha-particles were directed at a piece of thin gold foil

  25. Metal sheet coated With ZnS Lead block Uranium Gold Foil Chemist . Ahmed elfekey

  26. What he expected

  27. Because, he thought the mass was evenly distributed in the atom Chemist . Ahmed elfekey

  28. Because, he thought the mass was evenly distributed in the atom

  29. What he got • Ch. Ahmed elfekey

  30. + How he explained it Atom is mostly empty. Small dense, positive piece at center. Alpha particles are deflected by it if they get close enough. Chemist . Ahmed elfekey

  31. + Chemist . Ahmed elfekey

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