Alchemy Unit – Investigation IV

Lesson 1:

Island of Stability

QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

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?

Cu63

29Au

197

79

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

Isotope Review

Copper-63

29 protons

29 electrons

63 – 29 = 34 neutrons

Cu63

29Au

197

79

Bottom #: Number of protons

Top #: Total mass (protons + neutrons)

Gold-197

79 protons

79 electrons

197 – 79 = 118 neutrons

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

The Big Question

• What is the range of the number of neutrons found in isotopes of various elements?

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

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

© 2004 Key Curriculum Press.

Homework Review

1. Atomic # = number of protons

Atomic mass = average of mass numbers

Mass # = protons + neutrons

2. They have different numbers of neutrons and different masses.

3.

K4019K4119K3919

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

Homework Review

4. a) fluorine-23 p: 9 e: 9 n: 23 – 9 = 14

b) p: 27 e: 27 n: 59 – 27 = 32

c) molybdenum-96 p: 42 e: 42 n: 96 -42 = 54

d) p: 30 e: 30 n: 70 - 30 = 40

5. Mass = 26 + 32 = 58 amu

Zn7030

Fe5826

Co5927

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

Homework Review

6. Mass = 30.97 Atomic # = 15

Phosphorus-31 will be most abundant because 30.97 is closest to 31.

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

• 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.

Continuation of Isotope Notes from 9/27/10

(cont.)

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

• 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.)

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

• Isotopes have similar chemical properties in that they combine with other elements to form similar compounds.

(cont.)

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

Boron-10 Boron-11

Uranium-238

Atomic #

Mass #

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

• 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.

Atom Stability 9 / 28 / 10

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

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.)

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

(cont.)

(cont.)

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

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

© 2004 Key Curriculum Press.

• 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.

Notes

(cont.)

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

• Any isotope that is around long enough to be detected and measured qualifies as an element, but still can be highly unstable and radioactive.

(cont.)

Unit 1 • Investigation IV

© 2004 Key Curriculum Press.

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

© 2004 Key Curriculum Press.

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.