Atomic structure refers to the structure of an atom comprising a nucleus (center) in which the protons (positively charged) and neutrons (neutral) are present. The negatively charged particles called electrons revolve around the center of the nucleus.
1. Atomic Structure
2. Democritus 460 BC ► GreekPhilosopher ► Suggested world was made of two things – empty space and “atomos” Atomos – Greek word for uncuttable ►2 Main ideas Atoms are the smallest possible particle of matter There are different types of
3. John Dalton’s Atomic Theory 1804 1. All matter is made of atoms. 2. Atoms of one element are all the same. 3. Atoms cannot be broken down into smaller parts 4. Compounds form by combining atoms
4. Dalton’s Early Atomic Model ► “Billiard Ball” model ► he envisioned atoms as solid, hard spheres, like billiard(pool) balls, so he used wooden balls to model them
5. J.J. Thomson 1897 Discovered the electron He was the first scientist to show the atom was made of even smaller
6. JJ Thomson ► Used the Cathode ray tube to discover electrons
7. Thomson’s Experiment Voltage source - + Vacuum tube Metal Disks
8. Thomson’s Experiment Voltage source - +
9. Thomson’s Experiment Voltage source - +
10. Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end
11. Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end
12. Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end
13. Thomson’s Experiment Voltage source - + Passing an electric current makes a beam appear to move from the negative to the positive end
14. Thomson’s Experiment Voltage source ►By adding an electric field
15. Thomson’s Experiment Voltage source + - By adding an electric field
16. Thomson’s Experiment Voltage source + - By adding an electric field
17. Thomson’s Experiment Voltage source + - By adding an electric field
18. Thomson’s Experiment Voltage source + - By adding an electric field
19. Thomson’s Experiment Voltage source + - By adding an electric field
20. Thomson’s Experiment Voltage source + - - Adding an electric field cause the beam to move toward the positive plate. Thomson concluded the beam was made of negative moving pieces.
21. Thomson’s “Plum Pudding” Atom Model
22. Democritus, Dalton, Thomson Video
23. Eugen Goldstein 1850-1930 Using a cathode ray tube he discovered canal rays which are beams of positively charged He is credited with the discovery of protons in an atom. Canal Rays discovery
24. Millikan’s Oil Drop • Determined the charge on an electron • Used Thomson’s charge Millikan’s Oil Drop to mass Millikan’s Oil Drop ratio to calculate theExperiment Experiment mass video –of an another electron
25. Ernest Rutherford - 1913 • discovered the nucleus of a gold atom with his “gold foil” experiment
26.
27. Using J.J Thomson’s Plum Pudding atomic model, Rutherford predicted the alpha particles would pass straight though the gold foil. That’s not what happened.
28. Gold Foil Experiment Results most alpha particles go straight through the gold foil A few alpha particles are sharply
29. Rutherford’s Conclusion ►The atom is mostly empty space. ►There is a small, dense center with a positive charge. discovered the nucleus in atoms
30. Rutherford’s Contribution to the Atomic Theory ►The atom is mostly empty space. ►The nucleus is a small, dense core with a positive charge.
31. Gold Foil video
32. Rutherford’s Atomic Model
33. Structure of the Atom ► Atom – smallest particle of an element that can exist alone Two regions of an atom ►Nucleus Center of atom Protons and neutrons ►Electron “cloud” Area surrounding nucleus containing electrons
34. Structure of the Atom ► Proton – Positive charge (+), 1 atomic mass unit (amu); found in the nucleus amu -Approximate mass of a proton or a neutron ► Neutron – Neutral charge (0), 1 amu; found in the nucleus ► Electron – Negative charge (-), mass is VERY small
35. Counting Atoms ► Atomic Number Number of protons in nucleus The number of protons determines identity of the element!! ► Mass Number (Atomic Mass) Number of protons + neutrons
36. Counting Atoms ► Isotopes Atoms of the same element with varying number of neutrons Different isotopes have different mass numbers because the number of neutrons is different
37. Composition of the atom video Start at 3:25
38. Counting Atoms Nuclear Symbol Notation
39. Atoms ► Protonshave a positive (+) charge and electrons have a negative (-) charge ► Ina neutral atom, the number of protons equals the number of electrons, so the overall charge is zero (0) Example/ Helium, with an atomic number of 2, has 2 protons and 2 electrons when
40. Ions ► In a neutral atom Atomic number = # of protons = #of electrons ► Sometimes atoms will gain or lose electrons and form IONS ► Because an electron has a negative charge: When an atom GAINS electrons it becomes NEGATIVE When an atom LOSES electrons it
41. Ions Cation = a positive ion Anion = a negative ion
42. Let’s Practice ► Aluminum (Al) (no periodic table) Protons = 13 Electrons = Neutrons = 14 Atomic Number = Atomic Mass =
43. Let’s Practice w/ nuclear symbol notation ► NuclearSymbol notation (no periodic table) 108 A Protons = Electrons = 47 Neutrons = Atomic Number = Atomic Mass = g
44. Let’s Practice w/ isotopes ► use the periodic table Protons = Uranium- Electrons = Neutrons = 235 Atomic Number = Atomic Mass =
45. Let’s Practice with Ions Use the periodic table 39 K 1+ Charge = Protons = Electrons = Neutrons = Atomic Number = Atomic Mass =
+1-315-636-4485
+91 98151-74050 
