1. Investigation III: A Particulate World
Alchemy Unit
Investigation III: A Particulate World
Lesson 1: Pudding and Clouds
Lesson 2: Building Atoms
Lesson 3: Subatomic Heavyweights
Lesson 4: Life on the Edge
Lesson 5: Shell Game
Lesson 6: Go Figure
Lesson 7: Technicolor Atoms

2. Alchemy Unit – Investigation III
Lesson 1:
Pudding and Clouds

3. 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?
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4. The Big Question
How have chemists thought about the atom through history?
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5. You will be able to:
Describe some models of an atom and explain how they differ.
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6. Notes
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.
(cont.)
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7. As new evidence is gathered, models are refined and changed.
(cont.)
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.
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8. 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.
(cont.)
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9. (cont.)
Five Models of the Atom
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10. 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.
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11. Notes 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).
(cont.)
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12. Notes (cont.)
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.
(cont.)
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13. Notes (cont.)
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14. 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.
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15. 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.
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16. Alchemy Unit – Investigation III
Lesson 2:
Building Atoms

17. ChemCatalyst
A Bohr model of a helium atom and a beryllium atom are given below.
Helium, He
Berylium, Be
(cont.)
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18. List three similarities and three differences.
(cont.)
List three similarities and three differences.
How do you think a gold atom is different from a copper atom?
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19. The Big Question
What does the periodic table tells us about the structures of different atoms?
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20. You will be able to:
Use the periodic table to identify the properties of an elements atom.
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21. Notes
Atomic number is the number of protons in the nucleus of an atom.
Mass number is the mass of an individual atom.
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22. Activity
Purpose: This lesson will formally introduce you to atomic structure.
Beryllium Atom
Fluorine Atom
Carbon Atom
(cont.)
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23. (cont.) element chemical symbol atomic number # of protons
# of electrons
# of neutrons
mass number
atomic weight
beryllium 5
fluorine 10 6 12
chlorine 18
35.45
lead
126
potassium 19 39
tin 70
tungsten
184
183.85 29 36
gold
118
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24. 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.
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25. Notes
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.
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26. 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
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27. Wrap-Up
Each successive element has one more proton than the element preceding it.
The atomic number is equal to the number of protons.
(cont.)
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28. (cont.)
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).
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29. Alchemy Unit – Investigation III
Lesson 3:
Subatomic Heavyweights

30. 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.
(cont.)
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31. What is different about the two atoms?
(cont.)
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?
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32. The Big Question
How do isotopes of an atom account for the atomic weight of an element?
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33. You will be able to: Predict the isotopes of an element.
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34. Notes
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.
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35. Activity
Purpose: In this lesson you will investigate isotopes and how they affect atomic weight.
(cont.)
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36. (cont.) (cont.) boron atom 1 2 3 4 5 6 7 8 9 10 # protons # neutrons
# electrons
(cont.)
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37. (cont.) Element Chemical Symbol Atomic Number Atomic Weight
# of protons
# of electrons
# of neutrons
Boron B
5 or 6
Chlorine 17
Lithium
6.94
Vanadium V 23
Nitrogen 7
Magnesium
Argon Ar
39.9
or 22
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38. Making Sense
Explain why the atomic weights listed in the periodic table are not usually whole numbers.
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39. Notes
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.
(cont.)
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40. Notes (cont.)
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.
(cont.)
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41. (cont.)
Atomic Weight is the weighted average of the atomic masses of different isotopes taking into account their abundance.
(cont.)
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42. (cont.)
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43. Check-In
Predict the isotopes of carbon, C. Which isotope is more abundant? How do you know?
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44. 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.
(cont.)
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45. Isotopes are referred to by their mass numbers.
(cont.)
Isotopes of a single element exhibit similar properties in that they form similar compounds.
Isotopes are referred to by their mass numbers.
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46. Alchemy Unit – Investigation III
Lesson 4:
Life on the Edge

47. 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?
(cont.)
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48. (cont.)
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49. The Big Question
What accounts for the similar chemistry of elements in the same group?
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50. You will be able to:
Give the number of valence electrons for an element.
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51. 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.
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52. Making Sense
Explain how you can determine the arrangement of an element’s electrons, from the element’s position on the periodic table.
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53. Notes
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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54. (cont.)
(cont.)
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55. The outermost shell of each drawing is called the valence shell.
(cont.)
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.
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56. 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.
(cont.)
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57. e) The number of valence electrons.
(cont.)
e) The number of valence electrons.
f) The group number for this element.
g) The names of other elements with similar chemistry.
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58. 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.
(cont.)
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59. Elements with the same number of valence electrons have similar chemistry and are in the same group.
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60. Alchemy Unit – Investigation III
Lesson 5:
Shell Game

61. 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. 1 2 3 4 1s 2s
2pp
3sp
3pp 3d
4sp
4pp
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62. The Big Question
How do electron subshells relate to the periodic table?
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63. You will be able to:
Identify an element based on its electron configuration.
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64. Notes Electron shells are divided into electron subshells.
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65. Activity
Purpose: This lesson introduces you to electron subshells. You will explore how they are related to the periodic table.
(cont.)
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66. (cont.) 1s 2s
2pp
3sp
3pp 3d
4sp
4pp
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67. (cont.) Electron configuration Element 1s22s1 1s22s22p3 nitrogen, N
1s22s22p63s23p5
1s22s22p63s23p64s23d6
1s22s22p63s23p64s23d104p2
1s22s22p63s23p64s23d104p65s24d105p4
tellurium,Te
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68. Making Sense
How is the organization and structure of the periodic table related to electron subshells?
(cont.)
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69. (cont.)
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70. Notes
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.
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71. Check-In
Identify the element with the following electron configuration.
1s22s22p63s23p64s23d104p3
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72. 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.
(cont.)
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73. (cont.)
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.
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74. Alchemy Unit – Investigation III
Lesson 6:
Go Figure

75. 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.
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76. The Big Question
Where are the valence electrons in electron configurations?
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77. You will be able to:
Write electron configurations and name valence electrons for an element.
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78. Activity
Purpose: This activity teaches you a shorthand way to keep track of electron arrangements and how to identify valence electrons.
(cont.)
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79. (cont.) (cont.) Element Electron configuration
No. of valence electrons
Identity of valence electrons
1s22s22p3 5
2s22p3
1s22s22p63s23p1
1s22s22p63s23p64s23d2
2 or 4
4s23d2
1s22s22p4
Chlorine
1s22s22p63s23p64s23d104p65s1
Barium
(cont.)
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80. (cont.) (cont.) Element Electron configuration
No. of valence electrons
Identity of valence electrons
1s22s22p63s23p64s23d104p65s24d105p6
Silver
1 or 2
5s2
Potassium
Mercury 2
6s2
Terbium
Chromium
2,3,4,5,6
4s23d4
(cont.)
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81. (cont.) Element Electron configuration Valence electrons Lithium, Li
[He] 2s1
2s1
Potassium, K
[Ar] 4s1
4s1
Scandium, Sc
[Ar] 4s23d1
4s2 3d1
Zinc, Zn
[Ar] 4s23d10
4s2
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82. Making Sense
If you know the electron configuration of an element, what other information can you figure out? List at least six things.
(cont.)
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83. Unit 1 • Investigation III

84. 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.
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85. 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.
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86. Alchemy Unit – Investigation III
Lesson 7:
Technicolor Atoms

87. 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?
(cont.)
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88. Unit 1 • Investigation III

89. The Big Question What part of the atom is changed by heating?
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90. You will be able to:
Predict the color of the flame produced when heating a substance.
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91. Activity
Purpose: In this activity you will observe evidence that atomic structure is changed when atoms are heated.
(cont.)
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92. Keep long sleeves and clothing away from the flames.
(cont.)
Safety Note:
Tie back long hair.
Keep long sleeves and clothing away from the flames.
(cont.)
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93. (cont.)
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.
(cont.)
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94. Substance Name Color of Flame sodium carbonate potassium nitrate
copper nitrate
strontium nitrate
potassium chloride
sodium chloride
copper sulfate
strontium chloride
sodium nitrate
potassium sulfate
copper wire
copper penny
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95. 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?)
(cont.)
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96. (cont.)
Do you think gold can be made by changing the arrangement of electrons in atoms? Explain.
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97. Notes Red Blue/Green Yellow/Orange Pink/Lilac (cont.)
strontium nitrate
strontium chloride
Blue/Green
copper nitrate
copper sulfate
copper solid
copper penny
Yellow/Orange
sodium carbonate
sodium chloride
sodium nitrate
Pink/Lilac
potassium nitrate
potassium chloride
potassium sulfate
(cont.)
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98. Notes (cont.)
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99. Check-In
Predict the colors of the flames produced when heating the following substances. Explain your thinking.
Copper carbonate
Magnesium sulfate
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100. 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.
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