1. HHS-CHEM-2010/11

2. Chapter 4- page 86 “The Structure of the Atom” Chemistry Chemistry Humble High School Ms. B

3. Section 4.1 Early Theories of Matters Read p- 88 from “ The greek philosophers Democritus…to…John Dalton”. Describe Which of Dalton’s beliefs about the atom are wrong? Explain why. Explain Why were alpha particles deflected in Rutherford’s gold foil experiment? Identify HISTORY OF THE ATOM

4. 460 BC Democritus develops the idea of atoms he pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMA (greek for indivisible)

5. HISTORY OF THE ATOM 1808 John Dalton suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them ATOMS

6. HISTORY OF THE ATOM 1898 Joseph John Thompson found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRON

7. HISTORY OF THE ATOM Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge 1904 like plums surrounded by pudding. PLUM PUDDING MODEL Joseph John Thompson

8. HISTORY OF THE ATOM 1910 Ernest Rutherford He fired Helium nuclei at a piece of gold foil which was only a few atoms thick. He found that although most of them passed through. About 1 in 10,000 hit and bounced back.

9. HISTORY OF THE ATOM gold foil helium nuclei He found that while most of the helium nuclei passed through the foil, a small number were deflected and, to his surprise, some helium nuclei bounced straight back.

10. HISTORY OF THE ATOM Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus. He suggested that the positive charge was all in a central nucleus. With this holding the electrons in place by electrical attraction However, this was not the end of the story.

11. Rutherford’s problem: In the following pictures, there is a target hidden by a cloud. To figure out the shape of the target, we shot some beams into the cloud and recorded where the beams came out. Can you figure out the shape of the target? Target #1 Target #2

12. The Answers: Target #1 Target #2

13. HISTORY OF THE ATOM 1913 Niels Bohr studied under Rutherford at the Victoria University in Manchester. Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.

14. Bohr’s Atom electrons in orbits nucleus PLANETERE MODEL

16. I’m an electron! I’m a proton! I’m a neutron!

17. I was walking along and I saw these two. I was telling jokes to the neutron. The proton and I were having fun.

18. They looked so happy there together. I was p o s i t i v e l y charged! I couldn’t have amassed more happiness.

19. The proton looked happy, so I wandered closer. I could see the electron coming near. The who? Huh?

20. They were HUGE next to me! The electron was so tiny!! so cute! Like a speck of dust, or something…

21. I didn’t want to seem noisy, so I kept walking. Around and around the electron goes. Hey electron, you’re making the proton dizzy.

22. The proton seems so happy with the neutron. I’m having fun, but I still notice the electron. It won’t bother me if the electron hangs around.

23. I guess I’ll just wander around out here. I’m happy hanging out here. The center is cool, but sometimes it can be a “Bohring”.

24. Electrons circle around the nucleus of an atom. Protons are a main part of the nucleus of an atom. Neutrons also hang out in the nucleus of an atom.

25. Electrons have a negative charge.  Protons have a positive charge. + Neutrons have no charge. 0

26. Electrons are little and have a mass of almost zero. Protons are big and have a mass of one. Neutrons are also big and have a mass of one.

28. What is an atom ? Definition : p- 90. Read Defining an atom.

29. Sec4.2 Subatomic Particles and the Nuclear Atom Nucleus :center of the atom and Home of Protons and Neutrons. *Proton = atomic number Has a positive (+) charge Has a relative mass of 1 Determines the Element Found inside the nucleus

30. What is the structure of an atom? *Neutron Has no (0) charge Has a relative mass of 1 Determines the isotope –Isotopes are two of the same element with different masses Found inside the nucleus

31. What is the structure of an atom? Electron –Has a negative (-) charge –Has a relative mass of 0 (zero) –Determines the ion –Found outside the nucleus Bohr model – electrons are in specific energy levels Electron cloud model – electrons are in a random cloud

32. HELIUM ATOM + N N + - - proton electron neutron Shell What do these particles consist of?

33. ATOMIC STRUCTURE ParticleChargeMass (g) or amu Location Electron (e - ) 9.11 x 10 -28 Or 0 amu Electron cloud Proton (p + ) +1 1.67 x 10 -24 Or 1 amu Nucleus Neutron (n o )0 1.67 x 10 -24 Or 1 amuNucleus

34. Sect.4.3 How Atoms Differ Atomic number of an element is the number of protons in the nucleus of each atom of that element : it is what define an element Element# of protonsAtomic # Carbon66 Nitrogen77 Oxygen88

35. Mass number is the number of protons and neutrons in the nucleus of an isotope: Mass # = p + + n 0 Nuclidep+p+ n0n0 Mass # Oxygen - 10 -88 - 3115 8 18 Oxygen 16 Phosphorus 31 16 Sect.4.3 How Atoms Differ

36. What is a chemical symbol? Chemical symbol tells us what atom it is Always a CAPITAL LETTER, sometimes followed by a lower case letter Ex: Oxygen O; Nitrogen N; Sodium Na Copper Cu; Iron Fe Cobalt Co; Carbon Monoxide CO (Co is an element, CO is a compound)

37. ATOMIC STRUCTURE the number of protons and neutrons in an atom He 4 2 Atomic number (subscript) Atomic mass (superscript) number of electrons = number of protons Hint: mass # is always › Atomic # the number of protons in an atom

38. SymbolsBromine n Find each of these: a) number of protons: b) number of neutrons: c) number of electrons: d) Atomic number: e) Mass Number: Br

39. Symbols n If an element has an atomic number of 34 and a mass number of 78, what is the: a) number of protons: b) number of neutrons: c) number of electrons: d) complete symbol:

40. Symbols n If an element has 91 protons and 140 neutrons what is the a) Atomic number: b) Mass number: c) number of electrons: d) complete symbol:

41. Symbols n If an element has 78 electrons and 117 neutrons what is the a) Atomic number: b) Mass number: c) number of protons: d) complete symbol:

42. Isotopes Dalton was wrong about all elements of the same type being identical Atoms of the same element can have different numbers of neutrons. Thus, different mass numbers. These are called isotopes.

43. Naming Isotopes We can also put the mass number after the name of the element: carbon-12 carbon-14 uranium-235

44. Isotopes are atoms of the same element having different masses, due to varying numbers of neutrons. IsotopeProtonsElectronsNeutronsNucleus Hydrogen–1 (protium) 1 1 0 Hydrogen-2 (deuterium) 111 Hydrogen-3 (tritium) 112

45. Isotopes Elements occur in nature as mixtures of isotopes. Isotopes are atoms of the same element that differ in the number of neutrons.

46. Calculating Atomic Mass Problem 4-3 page 103 Practice problems # 15-16 page 104

47. Atomic number equals the number of or. Atomic mass equals the number of + The Atomic Structure - Atomic Math Challenge Atomic Number Symbol Name Atomic Mass protons electrons protons neutrons

49. Assignment: Finish the rest of the worksheet and turn it in to your teacher.

50. The first energy street can hold only two Electron. The second energy street, called the Energy Freeway, can hold 8 electrons. The third energy street, called the Energy Superhighway, can hold 18 of them. Nucleus Arcade Contains protons & neutrons Energy Freeway Can hold 8 (2,6) Energy Superhighway Can hold 18 electrons( 2,6,10) Energy Street Can hold 2 electrons

51. ATOMIC STRUCTURE There are two ways to represent the atomic structure of an element or compound; 1.Electronic Configuration 2.Dot & Cross Diagrams

52. ELECTRONIC CONFIGURATION With electronic configuration elements are represented numerically by the number of electrons in their shells and number of shells. For example: N Nitrogen 7 14 We know 2e in 1 st shell 5e in 2 nd shell 2 + 5 = 7 So, Nitrogen configuration = 2, 5

53. ELECTRONIC CONFIGURATION Write the electronic configuration for the following elements; Ca O ClSi Na 40 20 23 11 16 35 8 17 28 14 B 5 11 a)b)c) d)e)f) 2,8,8,2 2,8,1 2,8,72,8,4 2,3 2,6

54. DOT & CROSS DIAGRAMS With Dot & Cross diagrams elements and compounds are represented by Dots or Crosses to show electrons, and circles to show the shells. For example; Nitrogen N XX X X XX X N 7 14

55. DOT & CROSS DIAGRAMS Draw the Dot & Cross diagrams for the following elements; OCl 817 16 35 a)b) O X X X X X X X X Cl X X X XX X X X X X X X X X X X X X

56. SUMMARY 1.The building block of Matters is Atom; Definition of an atom 2.The subatomic particles are: Proton, Neutron, Electron. 3. a) Protons are +ve and defines the Element. b) Neutrons are neutral and defines the isotopes. c) Electrons are –ve and defines the chemical properties of the element. 4.Isotopes are atoms of the same element that differ in the number of neutrons. 5.The Atomic Number of an atom = number of protons in the nucleus. 6. The Atomic Mass of an atom = number of P + N in the nucleus. 7. The number of Protons = Number of Electrons= overall charge = 0 8. Electrons orbit the nucleus in shells. 9. Each shell can only carry a set number of electrons= 2,8,18

57. ATOMIC STRUCTURE Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. first shella maximum of 2 electrons second shella maximum of 8 (2,6) electrons third shella maximum of 18 (2,6,10) electrons

58. Chapter 5 p-116 Electrons in Atoms Read p-118