alchemy unit

1. Alchemy Unit Investigation III: A Particulate World

3. Unit 1 • Investigation III ChemCatalyst In the 5th century BCE a Greek philosopher named Leucippus and his student, Democritis, stated, “All matter is made up of particles that can be divided called atoms.” What do you think atoms are?

4. Unit 1 • Investigation III The Big Question How have chemists thought about the atom through history?

5. Unit 1 • Investigation III You will be able to: Describe some models of an atom and explain how they differ.

6. Unit 1 • Investigation III Atoms are extremely small particles, which cannot be seen, even with microscopes. All matter is made up of atoms. Scientists have created models to describe atoms. Models are similar to theories, but often include a picture or physical representation.

7. Unit 1 • Investigation III When a model is supported by scientific evidence it is often accepted by the scientific community. Scientific evidence is a collection of observations that many people have made. Everyone agrees on the same collection of observations. As new evidence is gathered, models are refined and changed.

8. Unit 1 • Investigation III Activity Purpose: This lesson will introduce you to various models for the atom that have appeared over the past two hundred years. The descriptions of five models of the atom are on a separate handout.

9. Unit 1 • Investigation III Five Models of the Atom

10. Unit 1 • Investigation III Making Sense Examine the date of the atomic evidence and then put the five models in the correct order of their introduction to the world of science.

11. Unit 1 • Investigation III An atom is mostly empty space. The rest consists of a nucleus, which is located in the very center of the atom, and electrons, which are located around the nucleus. The nucleus is very small (it would be nothing more than a tiny speck in our drawings, if we were to draw it to scale).

12. Unit 1 • Investigation III The nucleus is also very dense and consists of two types of particles—neutrons and protons. A neutron is a neutral particle with no charge on it. A proton is a positively charged particle. Tightly bound together, neutrons and protons make a positively charged nucleus.

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14. Unit 1 • Investigation III Check-In Here is a Bohr model of a carbon atom. List two things this model tells you about atoms. List something this model does not tell you about atoms.

15. Unit 1 • Investigation III Wrap-Up All matter is made up of extremely small particles called atoms. These particles are too small to be seen even with a microscope. Science is theoretical and dynamic. Models and theories are continually being revised, refined, or replaced with new models and theories.

16. Alchemy Unit – Investigation III Lesson 2: Building Atoms

17. Unit 1 • Investigation III ChemCatalyst A Bohr model of a helium atom and a beryllium atom are given below.

18. Unit 1 • Investigation III List three similarities and three differences. How do you think a gold atom is different from a copper atom?

19. Unit 1 • Investigation III The Big Question What does the periodic table tells us about the structures of different atoms?

20. Unit 1 • Investigation III You will be able to: Use the periodic table to identify the properties of an elements atom.

21. Unit 1 • Investigation III Atomic number is the number of protons in the nucleus of an atom. Mass number is the mass of an individual atom.

22. Unit 1 • Investigation III Activity Purpose: This lesson will formally introduce you to atomic structure.

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24. Unit 1 • Investigation III Making Sense If you know the atomic number of an element, what other information can you figure out about the atoms of that element? If you know the atomic number of an element, can you figure out how many neutrons an atom of that element has? Can you come up with a close guess? Explain.

25. Unit 1 • Investigation III Mass number is the number of protons plus the number of neutrons. Atomic mass is the “weight” or mass of a single atom. Atomic weight is the decimal number on the periodic table.

26. Unit 1 • Investigation III Check-In Use your periodic table to identify the following elements: a) Atomic number 18 b) Has three electrons c) Atomic mass of 16.0

27. Unit 1 • Investigation III Wrap-Up Each successive element has one more proton than the element preceding it. The atomic number is equal to the number of protons.

28. Unit 1 • Investigation III The number of electrons is equal to the number of protons (as long as the atom is neutral). The mass number is equal to the number of protons plus the number of neutrons (most of the mass is found in the nucleus).

29. Alchemy Unit – Investigation III Lesson 3: Subatomic Heavyweights

30. Unit 1 • Investigation III ChemCatalyst A chemist investigating a sample of lithium found that some atoms have a lower mass than other atoms. The chemist determined that the structures of the two types of atoms would be similar to the two drawings below.

31. Unit 1 • Investigation III What is different about the two atoms? What is the atomic number of each atom? What is the mass number of each atom? Do you think they are both lithium atoms? Why or why not?

32. Unit 1 • Investigation III The Big Question How do isotopes of an atom account for the atomic weight of an element?

33. Unit 1 • Investigation III You will be able to: Predict the isotopes of an element.

34. Unit 1 • Investigation III Atoms of the same element that have different numbers of neutrons are called isotopes. Atomic mass units (amu) are “invented” measurement units of the atomic mass.

35. Unit 1 • Investigation III Activity Purpose: In this lesson you will investigate isotopes and how they affect atomic weight.

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38. Unit 1 • Investigation III Making Sense Explain why the atomic weights listed in the periodic table are not usually whole numbers.

39. Unit 1 • Investigation III While the element iron is defined as being made up of neutral atoms with 26 protons and 26 electrons, not every iron atom has the same number of neutrons. Atoms that have the same number of protons but different numbers of neutrons are called isotopes.

40. Unit 1 • Investigation III What we call the atomic weight on the periodic table is actually the average atomic mass of that element’s naturally occurring isotopes. Isotopes have similar chemical properties in that they combine with other elements to form similar compounds.

41. Unit 1 • Investigation III Atomic Weight is the weighted average of the atomic masses of different isotopes taking into account their abundance.

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43. Unit 1 • Investigation III Check-In Predict the isotopes of carbon, C. Which isotope is more abundant? How do you know?

44. Unit 1 • Investigation III Wrap-Up Elements may have anywhere from 2 to 10 naturally occurring isotopes. The atomic weight of an element listed on the periodic table is actually the average mass of the naturally occurring isotopes of that element. Isotopes have the same number of protons and electrons, but different numbers of neutrons.

45. Unit 1 • Investigation III Isotopes of a single element exhibit similar properties in that they form similar compounds. Isotopes are referred to by their mass numbers.

46. Alchemy Unit – Investigation III Lesson 4: Life on the Edge

47. Unit 1 • Investigation III ChemCatalyst The three atoms below have similar reactivity and chemical behavior. Where are these elements located on the periodic table? What do you think might be responsible for their similar properties?

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49. Unit 1 • Investigation III The Big Question What accounts for the similar chemistry of elements in the same group?

50. Unit 1 • Investigation III You will be able to: Give the number of valence electrons for an element.

51. Unit 1 • Investigation III Activity Purpose: The various physical and chemical properties of the elements can be traced to the electrons. By studying electrons further we may be able to unlock the key to creating substances similar to gold. This lesson will reveal the arrangement of electrons within atoms.

52. Unit 1 • Investigation III Making Sense Explain how you can determine the arrangement of an element’s electrons, from the element’s position on the periodic table.

53. Unit 1 • Investigation III Bohr proposed that electrons could be found in different shells around the nucleus. The letter “n” is referred to as the quantum number.

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55. Unit 1 • Investigation III The outermost shell of each drawing is called the valence shell. The valence shell contains the valence electrons. All other electrons are considered core electrons.

56. Unit 1 • Investigation III Check-In Provide the following information for element number 34. a) The element’s name and symbol. b) The number of protons in the nucleus. c) The total number of electrons for this element. d) The number of core electrons for this element.

57. Unit 1 • Investigation III e) The number of valence electrons. f) The group number for this element. g) The names of other elements with similar chemistry.

58. Unit 1 • Investigation III Wrap-Up Electrons occupy different shells around the nucleus of an atom. Each electron shell can hold a specific maximum number of electrons. The valence electrons are in the outermost electron shell of an atom. Electrons that are not valence electrons are called core electrons.

59. Unit 1 • Investigation III Elements with the same number of valence electrons have similar chemistry and are in the same group.

60. Alchemy Unit – Investigation III Lesson 5: Shell Game

61. Unit 1 • Investigation III ChemCatalyst The two drawings show two ways of representing the electron arrangement of the element calcium, Ca. Name at least two differences. Name at least two similarities.

62. Unit 1 • Investigation III The Big Question How do electron subshells relate to the periodic table?

63. Unit 1 • Investigation III You will be able to: Identify an element based on its electron configuration.

64. Unit 1 • Investigation III Electron shells are divided into electron subshells.

65. Unit 1 • Investigation III Activity Purpose: This lesson introduces you to electron subshells. You will explore how they are related to the periodic table.

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68. Unit 1 • Investigation III Making Sense How is the organization and structure of the periodic table related to electron subshells?

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70. Unit 1 • Investigation III An electron configuration is a list of all the subshells that have electrons for a given element. The number of electrons in a subshell is specified as a superscripted number.

71. Unit 1 • Investigation III Check-In Identify the element with the following electron configuration. 1s22s22p63s23p64s23d104p3

72. Unit 1 • Investigation III Wrap-Up Electron shells can be divided further into subshells, referred to as; s, p, d, f. Each subshell can hold a specific maximum number of electrons. The s subshell can hold 2 electrons, the p subshell can hold 6, the d subshell can hold 10 electrons, and the f subshell can hold 14.

73. Unit 1 • Investigation III The periodic table can assist us in figuring out the sequence of filling the subshells with electrons. Chemists keep track of electrons and the subshells they are in by writing electron configurations.

74. Alchemy Unit – Investigation III Lesson 6: Go Figure

75. Unit 1 • Investigation III ChemCatalyst Consider the following electron configuration: 1s22s22p63s23p64s23d104p4 What element do you think is represented by this electron configuration? How many valence electrons do you think this element has? Explain your reasoning.

76. Unit 1 • Investigation III The Big Question Where are the valence electrons in electron configurations?

77. Unit 1 • Investigation III You will be able to: Write electron configurations and name valence electrons for an element.

78. Unit 1 • Investigation III Activity Purpose: This activity teaches you a shorthand way to keep track of electron arrangements and how to identify valence electrons.

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82. Unit 1 • Investigation III Making Sense If you know the electron configuration of an element, what other information can you figure out? List at least six things.

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84. Unit 1 • Investigation III Check-In Write the electron configuration for bromine, Br. Write the noble gas electron configuration for Br. How many valence electrons does Br have? Explain.

85. Unit 1 • Investigation III Wrap-Up The noble gases can be used as placeholders in the periodic table when writing electron configurations. In the d-block or transition elements we find some exceptions to the rules when determining valence electrons.

86. Alchemy Unit – Investigation III Lesson 7: Technicolor Atoms

87. Unit 1 • Investigation III ChemCatalyst The ancient alchemists heated atoms to try to change them into gold. Knowledge of atomic structure assists us in figuring out what parts of an atom can be changed. Let’s say we started with a lithium atom and changed different parts of the atom. Look at the lithium atom below and four possible changes to it. What would we end up with in each case?

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89. Unit 1 • Investigation III The Big Question What part of the atom is changed by heating?

90. Unit 1 • Investigation III You will be able to: Predict the color of the flame produced when heating a substance.

91. Unit 1 • Investigation III Activity Purpose: In this activity you will observe evidence that atomic structure is changed when atoms are heated.

92. Unit 1 • Investigation III Safety Note: Tie back long hair. Keep long sleeves and clothing away from the flames.

93. Unit 1 • Investigation III Note: Do not exchange wires. For each solution, only use the wire that is already in that solution. After you use the wire, be sure to put it back in the solution from which it came.

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95. Unit 1 • Investigation III Making Sense The yellow color of the flame for sodium indicates that the sodium atoms changed in some way when they were heated. Consider the following possibility that the electron configuration of sodium changed from [Ne]3s1 to [Ne]4p1. What is the difference between [Ne]3s1 and [Ne]4p1? (Are the total number of electrons the same? Are the electrons in the same locations?)

96. Unit 1 • Investigation III Do you think gold can be made by changing the arrangement of electrons in atoms? Explain.

97. Unit 1 • Investigation III Blue/Green copper nitrate copper sulfate copper solid copper penny

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99. Unit 1 • Investigation III Check-In Predict the colors of the flames produced when heating the following substances. Explain your thinking. Copper carbonate Magnesium sulfate

100. Unit 1 • Investigation III Wrap-Up Electrons can move between subshells within an atom. An energy exchange occurs when electrons move farther away from the nucleus, or when they return to their original subshell. Moving electrons within an atom does not change the identity of the atom.