1. Atoms and Atomic Structure

2. Law of Conservation of Mass Lavoisier (1743-1794) In a chemical reaction, matter is neither created nor destroyed. P. 57 Click on picture for movie

3. CuCO 3 (s)  CuO(s) + CO 2 (g) 123.6 g79.6 g? g

4. CuCO 3 (s)  CuO(s) + CO 2 (g) 123.6 g79.6 g44.0 g

5. CuCO 3 (s)  CuO(s) + CO 2 (g) 123.6 g79.6 g44.0 g 123.6 g79.6 g + 44.0 g=

6. Law of Definite Proportions Proost (1754-1826) Different samples of any pure compound contain the same elements in the same proportions by mass. P. 58

7. Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 Regardless of where the copper carbonate is found

8. Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain?

9. Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain? Cu / C = 5.3g / 1g = x / 20g

10. Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain? (5.3g / 1g)20g = x

11. Mass Ratio of Cu:O:C in copper carbonate Cu:O:C = 53:40:10 = 5.3 : 4: 1 If a sample of copper carbonate contains 20 g of carbon how many g of Cu will it contain? 106 g = x

12. Law of Multiple Proportions (John Dalton)  The masses of one element that can combine chemically with a fixed mass of another element are in a ratio of small whole numbers. 2C+O 2  2CO Carbon monoxide C+O 2  CO 2 Carbon dioxide P. 59 24 g32 g 12 g32 g 2:1

13. The idea of “whole numbers” suggests the presence of “individual” particle ATOMS !

14. Dalton’s Atomic Theory John Dalton (1766-1844) proposed an atomic theory 1.matter is composed, indivisible particles (atoms). 2.all atoms of a particular element are identical 3.different elements have different atoms 4.atoms combine in certain whole-number ratios 5.In a chemical reaction, atoms are merely rearranged to form new compounds; they are not created, destroyed, or changed into atoms of any other elements. P. 56-57

15. OK! Matter is made of ATOMS But what are ATOMS? What are ATOMS themselves made of?

16. Cathode–Ray Tube P. 61

17. J.J. Thompson (1856-1940)

18. Cathode Rays - JJ Thompson P. 62

19. Mass of an electron Experiments performed by Thompson together with those of Robert Millikan were able to show that an electron has a mass of 9.1 x 10 -28 g The mass of one atom of the lightest element, hydrogen, is 1.7 x 10 -24 g An electron is approx 1/2000th the mass of a H atom!

20. So the electron appears to be an insignificant part of the atom - from a mass point of view! How are electrons arranged inside an atom?

21. Thompson’s Plum Pudding Model of the Atom electron Diffuse positive charge

22. Ernest Rutherford (1871-1937)

23. Nucleus of the Atom Rutherford (1871-1937) P. 64 Click on picture for movie

25. Nucleus of the Atom Continued P. 64

26. Nucleus of the Atom Continued (Rutherford)  At the center of the atom is a very dense nucleus that accounts for almost all the mass of the atom and contains all the positive charge.  He named these positive particles protons.  Protons have a relative mass of 1 and a charge of +1. P. 64

27. Nucleus of the Atom Chadwick (1891-1974)  When atoms of beryllium were bombarded with alpha particles, new uncharged particles with mass identical to protons were emitted.  These uncharged particles were called neutrons.  Neutrons have a relative mass of 1 and a charge of zero. P. 64-65

28. Characteristics of the Three Basic Subatomic Particles P. 65

30. Arrangement of Subatomic Particles in the Atom P. 66

32. Atoms are mainly EMPTY SPACE !

33. And so are ALL OF US !

34. Our first direct look at the atomic world Get me out of here!

35. View of Atoms from STM

36. Scanning Tunneling Microscopy

38. Isotopes  Atoms of an element that have the same number of protons but different numbers of neutrons are called isotopes. A X X = symbol of element Z A = mass number Z = atomic number  The isotopes of sulfur are written: 32 S 33 S 34 S 36 S 16161616

39. Isotopes Continued Which of the following represent isotopes of the same element? Which element? 234 X 234 X 235 X 238 X 92 93 92 92

40. Answer: 234 U 234 Np 235 U 238 U 92 93 92 92 234 Np is not an isotope of Uranium. 93

41. Isotopes of Carbon 12 C 13 C 14 C 6 6 6

42. 12 C 13 C 14 C 6 6 6 12 - 6 = 6 neutrons 13 - 6 = 7 neutrons 14 - 6 = 8 neutrons Radioactive Isotopes of Carbon

43. Carbon-14 Dating Used to date archeological artifacts up to 60000 years old measures amount of radioactive 14 C left in a sample Amount of 14 C decreases with time will be discussed in detail in Ch 5

44. Isotopic Fingerprinting The ratio of stable isotopes (e.g. 13 C/ 12 C) in a substance will vary slightly depending on the origin of the substance for example, petroleum samples from different parts of the world will have different 13 C/ 12 C ratios How could such information be useful?

45. Time for some nuclear chemistry …let’s begin Ch 5

46. Periodic Table Mendeleev (1834-1907)  Atoms arranged by ascending atomic number  Horizontal rows called periods  Vertical columns called groups  Elements within a group have similar chemical properties

47. The Periodic Table

48. Properties of Alkali Metals and Halogens

49. Metals Metals have distinctive properties  Good conductors of heat and electricity  Shiny appearance  Ductile and malleable  Are light purple in periodic table that is on the inside cover of the book

50. Nonmetals  Do not conduct heat or electricity  Not ductile or malleable  Many exist as gases  Are green in periodic table that is on the inside cover of the book

51. Semimetals  Have properties that lie between those of metals and nonmetals  Are gold yellow in the periodic table that is on the inside cover of the book

52. REFERENCE www.langara.bc.ca/chemistry/A_Mosi/C11 17_Ch3.pptwww.langara.bc.ca/chemistry/A_Mosi/C11 17_Ch3.ppt