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

2. ChemCatalyst
A Bohr model of a helium atom and a beryllium atom are given below.
Helium, He
Berylium, Be
(cont.)
Unit 1 • Investigation III

3. List three similarities and three differences between Be and He.
(cont.)
List three similarities and three differences between Be and He.
How do you think a gold atom is different from a copper atom?
Unit 1 • Investigation III

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

5. You will be able to:
Use the periodic table to identify the properties of an element’s atoms.
Unit 1 • Investigation III

6. Notes & Definitions
Atomic number is the number of protons in the nucleus of an atom.
Mass number is the mass of an individual atom.
Unit 1 • Investigation III

7. Activity
Purpose: This lesson will formally introduce you to atomic structure by first looking at Bohr models.
Beryllium Atom
Fluorine Atom
Carbon Atom
(cont.)
Unit 1 • Investigation III

8. Answer the following questions:
Label the electrons, nucleus, neutrons and protons in the pictures on the worksheet.
Each atom is electrically neutral. Can you explain why?
How did you know which were the protons and which were the neutrons?
Is the nucleus of these atoms positive, negative or neutral? Explain.
Unit 1 • Investigation III

9. 5. Fill in the following table
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
Unit 1 • Investigation III

10. Answer the following questions:
6. How did you figure out the number of electrons?
7. How did you figure out the number of protons?
8. How did you figure out the number of neutrons?
9. How does the mass number of each atom compare to the atomic weight given on the periodic table?
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11. Question 10: Draw a nitrogen atom
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12. Answer:
Electrons
Neutrons
Protons
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13. 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.
Unit 1 • Investigation III

14. Making Sense #3
Examine Tellurium (Te) and Iodine (I) on the periodic table. What are their atomic numbers? What are their atomic weights?
Why do you think iodine’s atomic weight is less than tellurium’s, even though its atomic number is higher?
Can you find another example like this?
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15. revisions and additions
Notes & Definitions,
revisions and additions
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.
Unit 1 • Investigation III

16. Atomic Structure & Alchemy
How are gold and copper atoms different?
To change copper into gold, what would we have to do to a copper atom?
If you were trying to make gold from another substance, is there a better starting material than copper?
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17. 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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18. 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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19. (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).
Unit 1 • Investigation III