1. How to Use This Presentation To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” To advance through the presentation, click the right-arrow key or the space bar. From the resources slide, click on any resource to see a presentation for that resource. From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. You may exit the slide show at any time by pressing the Esc key. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu

2. Chapter Presentation Transparencies Image and Math Focus Bank Bellringers Standardized Test Prep Visual Concepts Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter menu Resources

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Atoms Table of Contents Section 1 Development of the Atomic Theory Section 2 The Atom Chapter 4

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Bellringer The following is a quote by Democritus (c. 460– c. 370 BCE). Paraphrase this quote in your own words in your science journal. “Color exists by convention, sweet by convention, bitter by convention; in reality nothing exists but atoms and the void.” What do you know about Democritus? And why are his thoughts important? Chapter 4

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Objectives Describe some of the experiments that led to the current atomic theory. Compare the different models of the atom. Explain how the atomic theory has changed as scientists have discovered new information about the atom. Chapter 4

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory The Beginning of the Atomic Theory Around 440 BCE, a Greek philosopher named Democritus thought that you would eventually end up with a particle that could not be cut. He called this particle an atom. From Aristotle to Modern Science Aristotle, another Greek philosopher, disagreed with Democritus’s ideas. He believed that you would never end up with a particle that could not be cut. Chapter 4

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory The Beginning of the Atomic Theory, continued Democritus was right, though: Matter is made of particles, which we call atoms. An atom is the smallest particle into which an element can be divided and still be the same substance. Chapter 4

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Dalton’s Atomic Theory Based on Experiments John Dalton published his atomic theory in 1803. His theory stated that all substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed. Atoms of the same element are exactly alike, and atoms of different elements are different. Atoms join with other atoms to make new substances. Not Quite Correct The atomic theory was then changed to describe the atom more correctly. Chapter 4

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Thompson’s Discovery of Electrons Thompson experimented with a cathode-ray tube like the one shown on the next slide. He discovered negatively charged particles that are now known as electrons. Like Plums in Pudding After learning that atoms contain electrons, Thompson proposed a new model of the atom. Thompson thought that electrons were mixed throughout an atom, like plums in a pudding. Chapter 4

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Chapter 4 Thompson’s Cathode-Ray Tube Experiment

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Rutherford’s Atomic “Shooting Gallery” In 1909, Ernest Rutherford aimed a beam of small, positively charged particles at a thin sheet of gold foil. The next slide shows his experiment. Surprising Results Rutherford expected the particles to pass right through the gold in a straight line. To Rutherford’s great surprise, some of the particles were deflected. Chapter 4

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Chapter 4 Rutherford’s Gold-Foil Experiment

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Where Are the Electrons? Far from the Nucleus Rutherford proposed that in the center of the atom is a tiny, positively charged part called the nucleus. Bohr’s Electron Levels In 1913, Niels Bohr proposed that electrons move around the nucleus in certain paths, or energy levels. Chapter 4

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Where Are the Electrons?, continued The Modern Atomic Theory According to the current theory, there are regions inside the atom where electrons are likely to found. These regions are called electron clouds. Chapter 4

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 4 Comparing Models of the Atom Section 1 Development of the Atomic Theory

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Bellringer Answer the following question: An atom is the smallest particle into which an element can be divided and still be that element. Now that scientists have learned that an atom is made up of even smaller particles, is this definition still accurate? Explain your answer in your science journal. Chapter 4

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Objectives Describe the size of an atom. Name the parts of an atom. State how atoms of different elements differ. State how isotopes differ. Calculate atomic masses. Describe the role of electrons in an atom. Chapter 4

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom How Small Is an Atom? Scientists know that aluminum is made of average- sized atoms. An aluminum atom has a diameter of about 0.00000003 cm. Chapter 4

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom What Is an Atom Made Of? The Nucleus Protons are positively charged particles in the nucleus. Neutrons are the particles of the nucleus that have no electrical charge. Outside the Nucleus Electrons are the negatively charged particles in atoms. Electrons are found around the nucleus within electron clouds. All the structures of the atom can be seen on the next slide. Chapter 4

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Chapter 4 Parts of an Atom

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom What Is an Atom Made Of? The Nucleus An atom’s nucleus contains positively charged particles called protons. The SI unit used to express the masses of particles in atoms is the atomic mass unit (amu). Each proton has a mass of about 1 amu. Neutrons are the particles of the nucleus that have no electrical charge. Chapter 4

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom What Is an Atom Made Of?, continued Outside the Nucleus Electrons are the negatively charged particles in atoms. Electrons are found around the nucleus within electron clouds. The charges of protons and electrons are opposite but equal, so their charges cancel out. Because an atom has no overall charge, it is neutral. Chapter 4

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom How Do Atoms of Different Elements Differ? Starting Simply The hydrogen atom has one proton and one electron. Now for Some Neutrons The helium atom has two protons, two neutrons, and two electrons. Chapter 4

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom How Do Atoms of Different Elements Differ?, continued Building Bigger Atoms For bigger atoms, simply add protons, neutrons, and electrons. Protons and Atomic Number The number of protons in the nucleus of an atom is the atomic number of that atom. All atoms of an element have the same atomic number. Chapter 4

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Isotopes Isotopes are atoms that have the same number of protons but have different numbers of neutrons. Chapter 4

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Isotopes, continued Properties of Isotopes An unstable atom is an atom with a nucleus that will change over time. This type of isotope is radioactive. Telling Isotopes Apart You can identify each isotope of an element by its mass number. The mass number is the sum of the protons and neutrons in an atom. Chapter 4

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Isotopes, continued Chapter 4

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Isotopes, continued Naming Isotopes To identify a specific isotope of an element, write the name of the element followed by a hyphen and the mass number of the isotope. Calculating the Mass of an Element The atomic mass of an element is the weighted average of the masses of all the naturally occurring isotopes of that element. Chapter 4

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Math Focus Chapter 4

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom The Important Role of Electrons The electrons at the outer layer of the atom are important to the atom’s interactions with its environment. Energy Levels Each electron cloud exists at a certain energy level. Chapter 4

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom The Important Role of Electrons, continued Ions: Electron-Proton Imbalance Valence electrons are at the outer edge of the atom, so they are the ones most likely to be lost if the atom loses electrons. The outermost energy level is also where the atom is most likely to gain electrons. Ions are formed when an atom loses or gains electrons, leaving an unequal number of protons and electrons. Chapter 4

32. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Atoms Use the terms below to complete the concept map on the next slide. Concept Mapping nucleus mass number isotopes protons atoms electrons atomic number neutrons Chapter 4

33. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 4 Atoms

34. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter 4 Atoms

35. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu End of Chapter 4 Show

36. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation For the following questions, write your answers on a separate sheet of paper. FCAT Chapter 4

37. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 1.British chemist and schoolteacher John Dalton published a theory that defined atoms in 1803. Included in his theory was the idea that atoms are small particles which cannot be divided. One of the first major challenges to this theory came nearly 100 years later. Another British scientist, J.J. Thomson, created an experiment using a cathode-ray tube and discovered the existence of negatively charged subatomic particles. What was the effect of this new information? Continued on next slide Chapter 4

38. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Question 1, continued A.Dalton’s theory was not changed and is still believed to be true. B.Dalton’s theory had to be modified in response to the new information. C.Two different theories of atoms were developed and used by different scientists. D.Thomson’s experiment was changed so that its results matched Dalton’s theory. Chapter 4

39. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Question 1, continued A.Dalton’s theory was not changed and is still believed to be true. B.Dalton’s theory had to be modified in response to the new information. C.Two different theories of atoms were developed and used by different scientists. D.Thomson’s experiment was changed so that its results matched Dalton’s theory. Chapter 4

40. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 2. The illustration below shows a model of an isotope of boron. What is the mass of the isotope shown? F.5 G.10 H.11 I.16 Chapter 4

41. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 2. The illustration below shows a model of an isotope of boron. What is the mass of the isotope shown? F.5 G.10 H.11 I.16 Chapter 4

42. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 3. What is the difference between an isotope and an ion? A.An isotope is an atom that has a different number of electrons than other atoms of the same element have. An ion is a particle that has an equal number of protons and neutrons. B.An isotope is an atom that has a different number of protons than other atoms of the same element have. An ion is a particle that has an equal number of protons and electrons. C.An isotope is an atom that has a different number of neutrons than other atoms of the same element have. An ion is a particle that has an unequal number of protons and electrons. D.An isotope is an atom that has a different number of protons than other atoms of the same element have. An ion is a particle that has an unequal number of protons and electrons. Chapter 4

43. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 3. What is the difference between an isotope and an ion? A.An isotope is an atom that has a different number of electrons than other atoms of the same element have. An ion is a particle that has an equal number of protons and neutrons. B.An isotope is an atom that has a different number of protons than other atoms of the same element have. An ion is a particle that has an equal number of protons and electrons. C.An isotope is an atom that has a different number of neutrons than other atoms of the same element have. An ion is a particle that has an unequal number of protons and electrons. D.An isotope is an atom that has a different number of protons than other atoms of the same element have. An ion is a particle that has an unequal number of protons and electrons. Chapter 4

44. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 4. British scientist Ernest Rutherford proposed a new model of the atom in 1911. The diagram below shows his model of the atom. Continued on next slide Chapter 4

45. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Question 4, continued 4. What did this model add to atomic theory? F.the idea that an atom has a dense, negatively charged nucleus with electrons surrounding the nucleus at a distance G.the idea that an atom has a dense, positively charged nucleus with electrons surrounding the nucleus at a distance H.the idea that an atom has a dense, neutrally charged nucleus with electrons surrounding the nucleus in an electron cloud I.the idea that an atom has a dense, positively charged nucleus with electrons surrounding the nucleus in an electron cloud Chapter 4

46. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Question 4, continued 4. What did this model add to atomic theory? F.the idea that an atom has a dense, negatively charged nucleus with electrons surrounding the nucleus at a distance G.the idea that an atom has a dense, positively charged nucleus with electrons surrounding the nucleus at a distance H.the idea that an atom has a dense, neutrally charged nucleus with electrons surrounding the nucleus in an electron cloud I.the idea that an atom has a dense, positively charged nucleus with electrons surrounding the nucleus in an electron cloud Chapter 4

47. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 5. Which one of the following is true of a neutron? A.A neutron has half the mass of a proton. B.A neutron has the same mass as an electron. C.A neutron is a little more massive than a proton. D.A neutron is a little more massive than an electron. Chapter 4

48. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 5. Which one of the following is true of a neutron? A.A neutron has half the mass of a proton. B.A neutron has the same mass as an electron. C.A neutron is a little more massive than a proton. D.A neutron is a little more massive than an electron. Chapter 4

49. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation 6. Austrian physicist Erwin Schrödinger and German physicist Werner Heisenberg expanded atomic theory in the 20th century. They accepted some of the work of earlier scientists, but they added to atomic theory with new ideas about electrons. They did not agree with Neils Bohr’s model that had electrons moving in definite paths around the nucleus of an atom. Schrödinger and Heisenberg concluded that one cannot know exactly where electrons are in an atom. One can only predict where electrons are likely to be found. Continued on next slide Chapter 4

50. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Question 6, continued 6. What was one of the main contributions of Schrödinger and Heisenberg to atomic theory? Current theory identifies regions where electrons are likely to be found. What are these regions called? Chapter 4

51. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Question 6, continued 6. What was one of the main contributions of Schrödinger and Heisenberg to atomic theory? Current theory identifies regions where electrons are likely to be found. What are these regions called? Full credit answers should include the following points: One of the main contributions of Schrödinger and Heisenberg was the idea that electrons do not travel in definite paths around the nucleus. Electron clouds are the regions where electrons are likely to be found, according to current atomic theory. Chapter 4

52. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Thompson’s Cathode-Ray Tube Experiment Chapter 4

53. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Chapter 4 Rutherford’s Gold-Foil Experiment

54. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Chapter 4

55. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Development of the Atomic Theory Chapter 4

56. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Chapter 4 Parts of an Atom

57. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Chapter 4

58. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Chapter 4

59. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Chapter 4

60. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Chapter 4

61. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Chapter 4

62. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Standardized Test Preparation Chapter 4

63. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 The Atom Math Focus Chapter 4