1. Alchemy Unit – Investigation IV
Lesson 1:
Island of Stability

2. Admit Slip
The isotope notation for an atom of copper and an atom of gold are given below.
How could you change a copper atom into a gold atom?
What would you need to change? Give specific numbers.
Why is this change called a nuclear reaction? Cu 63 29 Au
197 79
Unit 1 • Investigation IV

3. Cu Au Isotope Review 63 29 197 79 Copper-63 29 protons 29 electrons
Top #: Total mass (protons + neutrons) Cu 63 29 Au
197 79
Bottom #: Number of protons
Copper-63
29 protons
29 electrons
63 – 29 = 34 neutrons
Gold-197
79 protons
79 electrons
197 – 79 = 118 neutrons
Unit 1 • Investigation IV

4. The Big Question
What is the range of the number of neutrons found in isotopes of various elements?
Unit 1 • Investigation IV

5. Objective:
Students will be able to determine how many neutrons are required to make a stable element with a given number of protons.
Agenda:
Admit Slip
Homework Review
Notes
Island of Stability Homework:
Exit Slip Island of Stability – Lesson 1
Unit 1 • Investigation IV

6. Homework Review Atomic # = number of protons
Atomic mass = average of mass numbers
Mass # = protons + neutrons
They have different numbers of neutrons and different masses.
Unit 1 • Investigation IV

7. Homework Review 4. a) fluorine-23 p: 9 e: 9 n: 23 – 9 = 14
b) p: e: n: 59 – 27 = 32
c) molybdenum p: 42 e: 42 n: = 54
d) p: e: n: = 40
5. Mass = = 58 amu
Unit 1 • Investigation IV

8. Homework Review Mass = 30.97 Atomic # = 15
Phosphorus-31 will be most abundant because is closest to 31.
Unit 1 • Investigation IV

9. Continuation of Isotope Notes from 9/27/10
For example, iron atoms always have 26 protons and 26 electrons, but not always the same number of neutrons.
Because isotopes of an element have different amounts of neutrons, and protons + neutrons = mass, each isotope will have a different mass.
(cont.)
Unit 1 • Investigation IV

10. Atomic Mass is the weighted average of the atomic masses of that element’s naturally occurring isotopes, taking into account their abundance.
The atomic mass will be closest to the mass of the most abundant isotope.
For example, since lithium’s atomic mass is 6.94, the most abundant lithium isotope is Li-7.
(cont.)
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11. Isotopes have similar chemical properties in that they combine with other elements to form similar compounds.
(cont.)
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12. Boron-10 Boron-11 Uranium-238 Mass # Atomic #
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13. Atom Stability 9 / 28 / 10
Nuclear chemistry is the study of the nucleus of the atom.
The band of stability is the range in the number of neutrons for a given number of protons for isotopes that are found in nature.
Unit 1 • Investigation IV

14. Activity
Purpose: Some combinations of neutrons, electrons, and protons are not stable enough to be called elements. This lesson shows you how to predict the numbers of neutrons, electrons, and protons of the isotopes they are likely to find in nature.
(cont.)
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15. Unit 1 • Investigation IV

16. (cont.)
(cont.)
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17. Making Sense
What kind of generalization can you make about how the number of protons and neutrons are related to each other in the elements?
Unit 1 • Investigation IV

18. Notes
Radioactive elements are less stable because they decay over time as pieces of the nucleus break apart.
Atoms that exist for a long time are referred to as stable.
Radioactive atoms disappear over time and are referred to as unstable.
(cont.)
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19. (cont.)
Any isotope that is around long enough to be detected and measured qualifies as an element, but still can be highly unstable and radioactive.
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20. Exit Slip
Use your graph to determine how many neutrons you would need to make a stable element with 75 protons.
How many neutrons would make a radioactive element with 75 protons?
Unit 1 • Investigation IV

21. Wrap-Up
In order for an atom to be considered an element, it has to have a stable nucleus and exist long enough to be detected.
The neutron to proton ratio is an important factor in determining the stability of a nucleus.
Some isotopes are more stable than others. Unstable isotopes undergo nuclear decay to produce atoms with lower mass.
Unit 1 • Investigation IV